CO0021164-Public-Notice_Permit.pdf - Leadville Sanitation

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4300 Cherry Creek Drive S., Denver, CO 80246-1530 P 303-692-2000 www.colorado.gov/cdphe/wqcd

Colorado Discharge Permit System (CDPS) Fact Sheet to Permit Number CO0021164

LEADVILLE SANITATION DISTRICT, LEADVILLE SANITATION DISTRICT WWTP, LAKE COUNTY

Christine Wehner PUBLIC NOTICE VERSION

February 13, 2020

TABLE OF CONTENTS

I. INTRODUCTION .................................................................................... 1

I. TYPE OF PERMIT ......................................................................................... 2

II. FACILITY INFORMATION ............................................................................. 2

III. RECEIVING STREAM..................................................................................... 4

IV. FACILITY DESCRIPTION .............................................................................. 4

V. PERFORMANCE HISTORY ............................................................................ 6

VI. DISCUSSION OF EFFLUENT LIMITATIONS ................................................ 8

VII. ADDITIONAL TERMS AND CONDITIONS .................................................. 17

VIII. REFERENCES ............................................................................................ 22

IX. ATTACHMENTS ................................................................................... 24

X. PUBLIC NOTICE COMMENTS.............................................................. 24

I. INTRODUCTION

The National Pollutant Discharge Elimination System (NPDES) permit was created by Congress as the implementation tool under the Clean Water Act for the restriction of the quantity, rate, and concentration of pollutants that the point sources may discharge into water. The division, as the delegated authority for development and issuance of NPDES permits for the state of Colorado, is obligated to develop and issue NPDES permits in a manner that meets federal statutory requirements (the Clean Water Act, 33 U.S.C. § 1251 et seq.), state statutory requirements (the Colorado Water Quality Control Act, 25-8-101 et seq.) and state and federal regulations. Routine review is an integral aspect of the NPDES and the Colorado Discharge Permitting System (CDPS) program. The Clean Water Act incorporates a finite term for NPDES permits in order to allow for routine review of permit terms and conditions; the Colorado Water Quality Control Act similarly recognizes that the periodic renewal of permits is required. Routine review of CDPS permits provides a mechanism for the division and the public to scrutinize the existing conditions of the permit; to upgrade the permit requirements to reflect changing knowledge, law, or advances in science and technology; to ensure that the permit limits are protective of the most recent water quality classifications, standards, and antidegradation designations established by the Water Quality Control Commission; and, if necessary, to protect against human error by the permit writer introduced into previous permits. Routine review often results in the incorporation of new or different permit limitations or approaches. This fact sheet includes factors explaining the need for the proposed permit requirements, and presents evidence supporting the need for the proposed requirements, including information regarding pollutant potential and available controls, incidents of environmental damage, and permit violations. This fact sheet also includes some background information to provide context for the statutory and regulatory direction as to how permit terms and conditions are established.

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Water Quality Control Division Fact Sheet, Permit No.CO0021164

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II. TYPE OF PERMIT

A. Permit Type: Domestic – Major Municipal, Mechanical Plant, Seventh Renewal B. Discharge To: Surface Water

III. FACILITY INFORMATION

A. SIC Code: 4952 Sewerage Systems B. Facility Location: 13867 US Highway 24 S Leadville, CO

Latitude: 39.2291° N, Longitude: 106.3297° W

C. Permitted Feature: 001A, following disinfection and prior to mixing with the receiving stream. 39.2291° N, 106.3297° W

The location(s) provided above will serve as the point(s) of compliance

for this permit and are appropriate as they are located after all treatment and prior to discharge to the receiving water.

D. Facility Flows: 1.15 MGD E. Relevant Permit History and Summary of Major Changes From Last Renewal

On June 13, 2019, the division issued for public comment a draft renewal of CDPS permit CO0021164 for Leadville SD WWTF. The June 2019 draft permit included the following major changes from the previous permit renewal:

Updated antidegradation analysis for COARUA02b based on January 2014 baseline water quality.

Considered Yak Tunnel WWTF discharge to establish water quality and antidegradation-based effluent limitations.

Monitoring implemented for metals and sulfide based on facility type and size for future RP analysis.

Updated limitation for total mercury based on the NIL that will require a compliance schedule.

New limitations for dissolved cadmium and dissolved zinc based on the WQBELs require compliance schedules.

New limitation for nonylphenol based on the ADBAC.

A requirement to monitor effluent temperature at discharge location 001A is included in the permit.

The public comment period was extended and was closed on August 19, 2019. Changes made herein to the June 2019 Draft Renewal Permit In order to provide new information available since the June 2019 draft for public review and comment, the division is re-noticing this draft renewal to CDPS Permit CO0021164 for Leadville SD WWTF. Limited changes to the June 2019 draft document are included herein. Specifically:

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This fact sheet has been modified to rewrite this Section II.E in order to provide a relevant permit history and summary of changes since last draft.

Section I and Section VIII.H have been added to this fact sheet to reflect updates to template documents, and the document has been renumbered accordingly.

The cover page of the permit has been edited to reflect updates to the template documents.

Part I.A.1 of the permit has been updated to include the name of the receiving waters in the description of the permitted feature (outfall 001A).

Effluent temperature monitoring requirements have been removed from Part I.A.2 of the permit due to the lack of temperature standards on California Gulch (COARUA06). Part I.A.4 of the permit, Sections VI and VII of this fact sheet, and Section VI of the Fact Sheet, Attachment 1 (Water Quality Assessment) have been updated accordingly.

A requirement for an infiltration/inflow study has been added to the permit. Section IV.A of this fact sheet and Part I.A.4 of the permit have been updated accordingly.

Hardness for the establishment of metals standards, other than cadmium and zinc, was recalculated based on an average hardness. This is further explained in the Fact Sheet, Attachment 1 (Water Quality Assessment) Section III. WQBELs and ADBACs were recalculated accordingly.

A minor error in Section VI.B of the fact sheet has been corrected to indicate that the RP analysis for mercury is based on the NIL and that only a 30-day average limitation will be added to the permit.

Fact Sheet Attachment 1 (Water Quality Assessment) and Section VII of this Fact Sheet have been updated to include radionuclides and uranium as pollutants of concern. Monitoring for radionuclides and uranium has been added to the permit (Part I.A.2) due to the infiltration/inflow noted in the submitted alternatives analysis.

Fact Sheet Attachment 1 (Water Quality Assessment) and Section VII of this Fact Sheet have been updated to include BTEX and benzene as pollutants of concern. Limitations for BTEX and benzene have been added to the permit (Part I.A.2) due to the infiltration/inflow noted in the submitted alternatives analysis, and a compliance schedule has been added to the permit (Part I.B.6).

Section VI and VII of this fact sheet have been modified to include an updated performance history and RP analysis for total recoverable arsenic, potentially dissolved copper, and potentially dissolved lead. Part I.A.2 of the permit has been modified to include numeric limitations for these parameters (ICIS codes: 00978, 01306, and 01318) based on the WQBELs and the ADBACs.

Compliance dates for activities to meet dissolved cadmium, total mercury, and dissolved zinc limitations (Part I.B.6.a) have been adjusted (moved back) to reflect time passed since the June 2019 draft permit.

The time period to calculate two-year average effluent data before reporting requirements become effective have been adjusted in Part I.A.2 of the permit to reflect time passed since the June 2019 draft permit.

Comments received during the June 2019 draft public comment period have not been addressed in this February 2020 fact sheet and permit. All public comments are available for download and review at: https://environmentalrecords.colorado.gov/HPRMWebDrawer/Record?q=CO0021164 The division intends to address all public notice comments following this public notice period. Commenters are not required to resubmit comments that were previously submitted to the division.

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https://environmentalrecords.colorado.gov/HPRMWebDrawer/Record?q=CO0021164


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IV. RECEIVING STREAM A. Waterbody Identification: COARUA06 and COARUA02b, California Gulch and Arkansas River B. Water Quality Assessment:

An assessment of the stream standards, low flow data, and ambient stream data has been performed to determine the assimilative capacities for California Gulch for potential pollutants of concern. This information, which is contained in the Water Quality Assessment (WQA) for this receiving stream(s), also includes an antidegradation review, where appropriate. The Division’s Permits Section has reviewed the assimilative capacities to determine the appropriate water quality-based effluent limitations as well as potential limits based on the antidegradation evaluation, where applicable. The limitations based on the assessment and other evaluations conducted as part of this fact sheet can be found in Part I.A of the permit. Permitted Feature 001A will be the authorized discharge point to the receiving stream.

V. FACILITY DESCRIPTION

A. Collection System

The permittee operates a separate sewer system that conveys wastewater to the WWTF. Infiltration and inflow (I/I) into the collection system has been evaluated for this renewal. Inflow is water, other than wastewater, that enters a sewer system from sources such as roof leaders, cellar drains, yard drains, area drains, foundation drains, drains from springs and swampy areas, manhole covers, cross sections between storm drains and sanitary sewers, catch basins, cooling towers, storm waters, surface runoff, street wash waters or other drainage. Inflow does not include, and is distinguished from, infiltration. (40 CFR 35.2005 Definitions) Infiltration is water other than wastewater that enters a sewer system (including sewer service connections and foundation drains) from the ground through such means as defective pipes, pipe joints, connections, or manholes. Infiltration does not include, and is distinguished from, inflow. (40 CFR 35.2005 Definitions)

I/I is assessed by calculating the gallons per capita per day. Gallons per capita per day is calculated by using the daily average influent flows for the three maximum flow months during the past calendar year, reported in Part D of the facility’s permit application. If the data on the application is outdated or not reported in the application, the three maximum 30-day average influent flows for the past calendar year may be used instead. The facility reports the total estimated flows for residential, industrial, commercial, and also the population of the service area in Part C of the permit application. The calculation to determine gallons per capita per day is:

𝑔𝑎𝑙𝑙𝑜𝑛𝑠 𝑝𝑒𝑟 𝑐𝑎𝑝𝑖𝑡𝑎 𝑝𝑒𝑟 𝑑𝑎𝑦 = 𝑔𝑎𝑙. 𝑝𝑒𝑟 𝑑𝑎𝑦

𝑝𝑜𝑝𝑢𝑙𝑎𝑡𝑖𝑜𝑛 𝑋 %𝑟𝑒𝑠𝑖𝑑𝑒𝑛𝑡𝑖𝑎𝑙 𝑓𝑙𝑜𝑤𝑠

% 𝑟𝑒𝑠𝑖𝑑𝑒𝑛𝑡𝑖𝑎𝑙 𝑓𝑙𝑜𝑤𝑠 = 𝑟𝑒𝑠𝑖𝑑𝑒𝑛𝑡𝑖𝑎𝑙 𝑓𝑙𝑜𝑤𝑠

𝑟𝑒𝑠𝑖𝑑𝑒𝑛𝑡𝑖𝑎𝑙 + 𝑐𝑜𝑚𝑚𝑒𝑟𝑐𝑖𝑎𝑙 + 𝑖𝑛𝑑𝑢𝑠𝑡𝑟𝑖𝑎𝑙 𝑓𝑙𝑜𝑤𝑠 𝑋 100%

For this facility the average of the daily average influent flows for the maximum three flow months is 0.375 million gallons per day. Based on data submitted in the permit application, the facility’s

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percent of residential flows is 64%. Based on the service area population of 4000, the estimated influent flow is 59.7 gallons per capita per day.

Although the facility does not exceed the 120 gallons per capita per day threshold used by the division to screen for excessive infiltration, the facility has noted in a submitted alternatives analysis that infiltration/inflow may be a significant contributor to high influent mercury. Therefore, a requirement to address infiltration/inflow has been included in the permit.

B. Lift Stations

There are no lift stations in the service area.

C. Chemical Usage

The permittee stated in the application that they utilize two chemicals in their treatment process. The MSDS sheets have been reviewed and the following chemicals have been approved for use and are summarized in the following table.

Table V-1 – Chemical Additives

Chemical Name Purpose Constituents of

Concern

Chlorine, liquid Disinfection TRC

Clarifloc CE-2078 Biosolids removal None*

*Clarifloc CE-2078 is used for biosolids removal, and is removed and disposed of with biosolids. Therefore, it is not present in the effluent.

Chemicals deemed acceptable for use in waters that will or may be discharged to waters of the State are acceptable only when used in accordance with all state and federal regulations, and in strict accordance with the manufacturer’s site-specific instructions.

D. Treatment Facility, Facility Modifications and Capacities

The facility consists of an influent flow measuring device, one septage holding tank, two aeration basins, two clarifiers, and polishing pond, a chlorine contact chamber and a continuous effluent flow measuring device. The permittee has not performed any construction at this facility that would change the hydraulic capacity of 1.15 MGD or the organic capacity of 2600 lbs BOD5/day, which were specified in Site Approval 3723. That document should be referred to for any additional information.

Pursuant to Section 100.5.2 of the Water and Wastewater Facility Operator Certification Requirements, this facility will require a certified operator. If the facility has a question on the level of the certified operator it needs then the facility will need to contact the Engineering Section of the Division.

E. Biosolids Treatment and Disposal

Biosolids are treated in two aerobic digesters to thicken the sludge prior to de-watering with a filter belt press. Then, the biosolids are hauled to an approved landfill.

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1. EPA Regulation

The Facility is required under the Direct Enforceability provision of 40 CFR §503.3(b) to meet the applicable requirements of the regulation.

2. Biosolids Regulation (Regulation No. 64, Colorado Water Quality Control Commission)

Colorado facilities that land apply biosolids must comply with requirements of Regulation No. 64, such as the submission of annual reports as discussed later in this fact sheet.

VI. PERFORMANCE HISTORY

A. Monitoring Data

1. Discharge Monitoring Reports – The following tables summarize the effluent data reported on the Discharge Monitoring Reports (DMRs) for the previous permit term, from January 2014 through December 2018.

Table VI-1 – Summary of DMR Data for Permitted Feature 001A

Parameter

# Samples or

Reporting Periods

Reported Average Concentrations Avg/Min/Max

Reported Maximum

Concentrations Avg/Min/Max

Previous Avg/Max/AD Permit Limit

Number of Limit

Excursions

Influent Flow (MGD) 60 0.36/0.28/0.54 0.44/0.32/0.76 Report/Report

Effluent Flow (MGD) 60 0.32/0.26/0.46 0.46/0.3/0.89 NA/0.205

pH (su) 60 7.2/6.8/8.2 8/1.7/9 NA - NA

Fecal Coliform (#/100 ml) 2 472/231/713 1270/910/1630 NA/NA

E. coli (#/100 ml) 58 49/10/455 336/10/1140 630/1260

TRC (mg/l) 60 0.12/0.02/0.31 0.24/0.04/0.42 0.34/0.44

NH3 as N, Tot (mg/l) Jan 5 4/1.1/11 4.6/1.3/12 20/NA

NH3 as N, Tot (mg/l) Feb 5 4.3/1.3/12 5.2/1.6/15 20/NA

NH3 as N, Tot (mg/l) Mar 5 5.3/1.6/12 6.8/1.8/15 20/NA

NH3 as N, Tot (mg/l) Apr 5 4.4/1.2/12 6.4/1.4/16 20/NA

NH3 as N, Tot (mg/l) May 5 2.9/0.95/6.7 4.8/1.2/10 20/NA

NH3 as N, Tot (mg/l) Jun 5 7.1/1.7/11 8.8/2.3/14 20/NA

NH3 as N, Tot (mg/l) Jul 5 11/7.1/14 13/9.7/15 20/NA

NH3 as N, Tot (mg/l) Aug 5 12/4.3/19 15/5.6/26 20/NA

NH3 as N, Tot (mg/l) Sep 5 11/1.9/20 15/2.6/30 20/NA

NH3 as N, Tot (mg/l) Oct 5 13/3.7/19 16/5.9/28 20/NA

NH3 as N, Tot (mg/l) Nov 5 9.8/1.2/14 13/1.4/18 20/NA

NH3 as N, Tot (mg/l) Dec 5 5.4/1.9/7.5 6.9/2.7/9.2 20/NA

BOD5, influent (mg/l) 60 198/138/257 200/138/281 NA/NA/

BOD5, influent (lbs/day) 60 572/230/966 631/230/1004 NA/NA/

BOD5, effluent (mg/l) 60 5.9/1.2/27 5.9/1.2/27 30/45/

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BOD5 (% removal) 59 97/85/100 NA/NA/NA 85/NA/

TSS, influent (mg/l) 60 194/120/279 196/120/303 NA/NA/

TSS, effluent (mg/l) 60 6.7//29 6.8//29 30/45/

TSS (% removal) 59 97/85/100 NA/NA/NA 85/NA/

Oil and Grease (mg/l) 60 NA/NA/NA 0/0/0 NA/NA/

Mo, TR (µg/l) 58 0.59/0.0005/2 NA/NA/NA NA/NA

Hg, Tot (µg/l) 58 0.063/0.0003/0.26 NA/NA/NA 0.077/NA 3

Zn, Dis (µg/l) 20 105/20/314 105/20/314 NA/NA

Nonylphenol (µg/l) 20 0//0 0//0 NA/NA

*The pH data shows the minimum reported values in the "average" column, and the maximum reported values in the "maximum column *The temperature data shows the MWAT values in the "average" column, and the daily maximum reported values in the "maximum column

** Geometric mean NA means Not Applicable NV means No Visible Sheen

Table VI-2 – Summary of DMR Data for Permitted Feature 001A (December 2007 through December 2013)

Parameter

# Samples or

Reporting Periods

Reported Average Concentrations Avg/Min/Max

Reported Maximum

Concentrations Avg/Min/Max

Previous Permit Limit

Number of Limit

Excursions

As, TR (µg/l) 13 0.56/0.0/1.4 0.7/0.0/1.6 Report

Cu, PD (µg/l) 13 3.2/1.5/4.3 3.2/1.5/4.3 Report

Pb, PD (µg/l) 13 0.51/0.2/1.0 NA/NA/NA Report

B. Compliance With Terms and Conditions of Previous Permit

1. Effluent Limitations –The data shown in the preceding table(s) indicate apparent violations of the permit. In August 2017, September 2018, and December 2018, the permittee violated effluent limitations for total mercury. Compliance advisories were issued for the August 2017 and September 2018 violations. The facility responded that they are working to sample various locations in the collection system to identify the source of mercury and have budgeted additional funds for mercury testing. In accordance with 40 CFR Part 122.41(a), any permit noncompliance constitutes a violation of the Clean Water Act and is grounds for enforcement action; for permit termination, revocation and reissuance, or modification; or denial of a permit renewal application.

2. Other Permit Requirements – The permittee has not met the following conditions of the permit:

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The permittee missed the following compliance schedule event for activities to meet total mercury final limits: CS017 - Achieve Final Compliance with Emission or Discharge Limits (6/30/2017). On November 9, 2018, the Leadville Sanitation District WWTF was served with a Notice of Violation / Cease and Desist Order relating to effluent and monitoring violations for Mercury.

The permittee has been in compliance with all other aspects of the previous permit.

VII. DISCUSSION OF EFFLUENT LIMITATIONS

A. Regulatory Basis for Limitations

1. Technology Based Limitations a. Federal Effluent Limitation Guidelines – The Federal Effluent Limitation Guidelines for

domestic wastewater treatment facilities are the secondary treatment standards. These standards have been adopted into, and are applied out of, Regulation 62, the Regulations for Effluent Limitations.

b. Regulation 62: Regulations for Effluent Limitations – These Regulations include effluent

limitations that apply to all discharges of wastewater to State waters and are shown in Section VIII of the WQA. These regulations are applicable to the discharge from the Leadville Sanitation District WWTF.

2. Numeric Water Quality Standards - The WQA contains the evaluation of pollutants limited by

water quality standards. The mass balance equation shown in Section VI of the WQA was used for most pollutants to calculate the potential water quality based effluent limitations (WQBELs), M2, that could be discharged without causing the water quality standard to be violated. For ammonia, the AMMTOX Model was used to determine the maximum assimilative capacity of the receiving stream. A detailed discussion of the calculations for the maximum allowable concentrations for the relevant parameters of concern is provided in Section VI of the Water Quality Assessment developed for this permitting action. The maximum allowable pollutant concentrations determined as part of these calculations represent the calculated effluent limits that would be protective of water quality. These are also known as the water quality-based effluent limits (WQBELs). Both acute and chronic WQBELs may be calculated based on acute and chronic standards, and these may be applied as daily maximum (acute) or 30-day average (chronic) limits.

3. Narrative Water Quality Standards - Section 31.11(1)(a)(iv) of The Basic Standards and

Methodologies for Surface Waters (Regulation No. 31) includes the narrative standard that State surface waters shall be free of substances that are harmful to the beneficial uses or toxic to humans, animals, plants, or aquatic life.

a. Whole Effluent Toxicity - The Water Quality Control Division has established the use of WET

testing as a method for identifying and controlling toxic discharges from wastewater treatment facilities. WET testing is being utilized as a means to ensure that there are no discharges of pollutants "in amounts, concentrations or combinations which are harmful to the beneficial uses or toxic to humans, animals, plants, or aquatic life" as required by Section 31.11 (1) of the Basic Standards and Methodologies for Surface Waters. The requirements for

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WET testing are being implemented in accordance with Division policy, Implementation of the Narrative Standard for Toxicity in Discharge Permits Using Whole Effluent Toxicity (Sept 30, 2010).

4. Water Quality Regulations, Policies, and Guidance Documents

a. Antidegradation - Since the receiving water is Undesignated, an antidegradation review is

required pursuant to Section 31.8 of The Basic Standards and Methodologies for Surface Water. As set forth in Section VII of the WQA, an antidegradation evaluation was conducted for pollutants when water quality impacts occurred and when the impacts were significant. Based on the antidegradation requirements and the reasonable potential analysis discussed below, antidegradation-based average concentrations (ADBACs) may be applied.

According to Division procedures, the facility has three options related to antidegradation-

based effluent limits: (1) the facility may accept ADBACs as permit limits (see Section VII of the WQA); (2) the facility may select permit limits based on their non-impact limit (NIL), which would result in the facility not being subject to an antidegradation review and thus the antidegradation-based average concentrations would not apply (the NILs are also contained in Section VII of the WQA); or (3) the facility may complete an alternatives analysis as set forth in Section 31.8(3)(d) of the regulations which would result in alternative antidegradation-based effluent limitations.

The effluent must not cause or contribute to an exceedance of a water quality standard and

therefore the WQBEL must be selected if it is lower than the NIL. Where the WQBEL is not the most restrictive, the discharger may choose between the NIL or the ADBAC: the NIL results in no increased water quality impact; the ADBAC results in an “insignificant” increase in water quality impact. The ADBAC limits are imposed as two-year average limits.

b. Antibacksliding - As the receiving water is designated Reviewable or Outstanding, and the

Division has performed an antidegradation evaluation, in accordance with the Antidegradation Guidance, the antibacksliding requirements in Regulation 61.10 have been met.

c. Determination of Total Maximum Daily Loads (TMDLs) – Stream segment COARUA06 is not on

the State’s 303(d) list, and therefore TMDLs do not apply. For stream segment, COARUA02b, this fact sheet and the accompanying permit include TMDLs developed as specified in Total Maximum Daily Load Assessment for the Arkansas River/Lake Creek/Chalk Creek/ Evans Gulch/Lake/Chaffee County, Colorado. However, there are no WLAs for dissolved cadmium and dissolved zinc specified for this facility. As required under the Clean Water Act Section 303(d), these TMDLs were submitted, through the normal public notification process, to EPA Region VIII for their review and approval, and were approved on July 14, 2009.

d. Colorado Mixing Zone Regulations – Pursuant to section 31.10 of The Basic Standards and

Methodologies for Surface Water, a mixing zone determination is required for this permitting action. The Colorado Mixing Zone Implementation Guidance, dated April 2002, identifies the process for determining the meaningful limit on the area impacted by a discharge to surface water where standards may be exceeded (i.e., regulatory mixing zone). This guidance document provides for certain exclusions from further analysis under the regulation, based on site-specific conditions.

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The guidance document provides a mandatory, stepwise decision-making process for determining if the permit limits will not be affected by this regulation. Exclusion, based on Extreme Mixing Ratios, may be granted if the ratio of the facility design flow to the chronic low flow (30E3) is greater than 2:1. Since the receiving stream has a low flow of zero, the facility is exempt from a mixing zone study.

e. Reasonable Potential Analysis – Using the assimilative capacities contained in the WQA, an

analysis must be performed to determine whether to include the calculated assimilative capacities as WQBELs in the permit. This reasonable potential (RP) analysis is based on the Determination of the Requirement to Include Water Quality Standards-Based Limits in CDPS Permits Based on Reasonable Potential, dated December, 2002. This guidance document utilizes both quantitative and qualitative approaches to establish RP depending on the amount of available data.

A qualitative determination of RP may be made where ancillary and/or additional treatment technologies are employed to reduce the concentrations of certain pollutants. Because it may be anticipated that the limits for a parameter could not be met without treatment, and the treatment is not coincidental to the movement of water through the facility, limits may be included to assure that treatment is maintained.

A qualitative RP determination may also be made where a federal ELG exists for a parameter,

and where the results of a quantitative analysis results in no RP. As the federal ELG is typically less stringent than a limitation based on the WQBELs, if the discharge was to contain concentrations at the ELG (above the WQBEL), the discharge may cause or contribute to an exceedance of a water quality standard.

To conduct a quantitative RP analysis, a minimum of 10 effluent data points from the previous 5 years, should be used. The equations set out in the guidance for normal and lognormal distribution, where applicable, are used to calculate the maximum estimated pollutant concentration (MEPC). For data sets with non-detect values, and where at least 30% of the data set was greater than the detection level, MDLWIN software is used consistent with Division guidance to generate the mean and standard deviation, which are then used to establish the multipliers used to calculate the MEPC. If the MDLWIN program cannot be used the Division’s guidance prescribes the use of best professional judgment. For some parameters, recent effluent data or an appropriate number of data points may not be available, or collected data may be in the wrong form (dissolved vs total) and therefore may not be available for use in conducting an RP analysis. Thus, consistent with Division procedures, monitoring will be required to collect samples to support a RP analysis and subsequent decisions for a numeric limit. A compliance schedule may be added to the permit to require the request of an RP analysis once the appropriate data have been collected. For other parameters, effluent data may be available to conduct a quantitative analysis, and therefore an RP analysis will be conducted to determine if there is RP for the effluent discharge to cause or contribute to exceedances of ambient water quality standards. The guidance specifies that if the MEPC exceeds the maximum allowable pollutant concentration (MAPC), limits must be established and where the MEPC is greater than half the MAPC (but less than the MAPC), monitoring must be established. Table VII-1 contains the calculated MEPC compared to the corresponding MAPC, and the results of the reasonable potential evaluation, for those parameters that met the data requirements. The RP determination is discussed for each parameter in the text below.

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Table VII-1 – Quantitative Reasonable Potential Analysis

Parameter

30-Day Average 7-Day Ave or Daily Max Antideg (2 Year Roll. Ave)

MEPC WQBEL (MAPC)

Reasonable Potential

MEPC WQBEL (MAPC)


MEPC ADBAC (MAPC)


Mo, TR (µg/l) 2.2 1150 No NA NA NA 1.1 176 No

Hg, Tot (µg/l) 0.29 0.04 Yes NA NA NA NA NA NA

Zn, Dis (µg/l) 440 215 Yes 440 253 Yes NA NA NA

B. Parameter Evaluation

BOD5 - The BOD5 concentrations in Reg 62 are the most stringent effluent limits and are therefore applied. These limitations are the same as those contained in the previous permit and are imposed upon the effective date of this permit.

Total Suspended Solids - The TSS concentrations in Reg 62 are the most stringent effluent limits and are therefore applied. These limitations are the same as those contained in the previous permit and are imposed upon the effective date of this permit. Oil and Grease –The oil and grease limitations from the Regulations for Effluent Limitations are applied as they are the most stringent limitations. This limitation is the same as those contained in the previous permit and is imposed upon the effective date of this permit. pH - This parameter is limited by the water quality standards of 6.5-9.0 s.u., as this range is more stringent than other applicable standards. This limitation is the same as that contained in the previous permit and is imposed upon the effective date of this permit.

E. Coli –The limitation for E. Coli is based upon the WQBEL as described in the WQA. A qualitative determination of RP has been made as the treatment facility has been designed to treat specifically for this parameter. This limitation is the same as those contained in the previous permit and is imposed upon the effective date of this permit. Total Residual Chlorine (TRC) - The limitation for TRC is based upon the WQBEL and the 2002 chlorine decay study conducted by Leadville Sanitation District as described in the WQA. A qualitative determination of RP has been made as chlorine may be used in the treatment process. Previous monitoring as shown in Table VI-1 indicate that this limitation can be met and is therefore imposed upon the effective date of the permit. The permittee is advised to update this study for consideration in the next renewal.

Ammonia - The limitation for ammonia is based upon the WQBEL as described in the WQA. A qualitative determination of RP has been made as the treatment facility has been designed to treat specifically for this parameter. Previous monitoring as shown in Table V-1 indicate that this limitation can be met and is therefore imposed upon the effective date of the permit.

Total Arsenic – The RP analysis for total recoverable arsenic was based upon the WQBEL of 58 µg/l

and the ADBAC of 8.4 µg/l. There were no data from the previous permit term regarding the presence/absence or quantification of this parameter in the discharge, but effluent data submitted by the facility between from December 2007 through December 2013 is available. Total recoverable

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arsenic was as high as 1.6 µg/l compared with an ADBAC of 8.4 µg/l. A qualitative determination of RP has been made for total arsenic based on the facility type, size, documented infiltration/inflow, and the presence of this parameter in the effluent. A numeric limitation will be included in the permit in accordance with the Reasonable Potential Policy (CW-1) because this parameter is present in the effluent in order to assure source control and/or treatment is maintained. Previous monitoring as shown in Table VI-2 indicate that this limitation can be met and is therefore imposed upon the effective date of the permit. Note that there is a two year delay to calculate the ADBAC. Dissolved Arsenic - There were no data from the previous permit term regarding the presence/absence or quantification of this parameter in the discharge. A qualitative determination of RP has been made based on the facility type and size. Since the potential exists for this parameter to be present, monitoring has been added to the permit for future RP analysis. Potentially Dissolved Cadmium – The limitation for dissolved cadmium is based upon the WQBEL as described in the WQA. A qualitative RP analysis was conducted as there were no data from the previous permit term conduct a quantitative RP analysis. A qualitative determination of RP has been made based on the facility type and size in addition to the TMDL for dissolved cadmium on the segment. Since the potential exists for this parameter to be present, a daily maximum and 30-day average limitation has been added to the permit. Note that the limitations are set equal to the water quality standard due to the impairment on the segment. It is unknown if the permittee can consistently meet this limitation and therefore a compliance schedule has been added to the permit to give the permittee time to meet this limitation. Reporting will be required in the interim. Total Recoverable Trivalent Chromium - There were no data from the previous permit term regarding the presence/absence or quantification of this parameter in the discharge. A qualitative determination of RP has been made based on the facility type and size. Since the potential exists for this parameter to be present, monitoring has been added to the permit for future RP analysis. Potentially Dissolved Trivalent Chromium – There were no data from the previous permit term regarding the presence/absence or quantification of this parameter in the discharge. A qualitative determination of RP has been made based on the facility type and size. Since the potential exists for this parameter to be present, monitoring has been added to the permit for future RP analysis. Dissolved Hexavalent Chromium – There were no data from the previous permit term regarding the presence/absence or quantification of this parameter in the discharge. A qualitative determination of RP has been made based on the facility type and size. Since the potential exists for this parameter to be present, monitoring has been added to the permit for future RP analysis. Potentially Dissolved Copper – The RP analysis for potentially dissolved copper was based upon the

WQBEL of 47 µg/l and the ADBAC of 9.0 µg/l. There were no data from the previous permit term regarding the presence/absence or quantification of this parameter in the discharge, but effluent data submitted by the facility between from December 2007 through December 2013 is available.

Potentially dissolved copper was as high as 4.3 µg/l compared with an ADBAC of 9.0 µg/l. A qualitative determination of RP has been made for potentially dissolved copper based on the facility type, size, documented infiltration/inflow, and the presence of this parameter in the effluent. A numeric limitation will be included in the permit in accordance with the Reasonable Potential Policy (CW-1) because this parameter is present in the effluent in order to assure source control and/or

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treatment is maintained. Previous monitoring as shown in Table VI-2 indicate that this limitation can be met and is therefore imposed upon the effective date of the permit. Note that there is a two year delay to calculate the ADBAC. Cyanide- There were no data from the previous permit term regarding the presence/absence or quantification of this parameter in the discharge. A qualitative determination of RP has been made based on the facility type and size. Since the potential exists for this parameter to be present, monitoring has been added to the permit for future RP analysis. Total Recoverable Iron - There were no data from the previous permit term regarding the presence/absence or quantification of this parameter in the discharge. A qualitative determination of RP has been made based on the facility type and size. Since the potential exists for this parameter to be present, monitoring has been added to the permit for future RP analysis.

Potentially Dissolved Lead - The RP analysis for potentially dissolved lead was based upon the WQBEL

of 11 µg/l and the ADBAC of 2.6 µg/l. There were no data from the previous permit term regarding the presence/absence or quantification of this parameter in the discharge, but effluent data submitted by the facility between from December 2007 through December 2013 is available.

Potentially dissolved lead was as high as 1.0 µg/l compared with an ADBAC of 2.6 µg/l. A qualitative determination of RP has been made for potentially dissolved lead based on the facility type, size, documented infiltration/inflow, and the presence of this parameter in the effluent. A numeric limitation will be included in the permit in accordance with the Reasonable Potential Policy (CW-1) because this parameter is present in the effluent in order to assure source control and/or treatment is maintained. Previous monitoring as shown in Table VI-2 indicate that this limitation can be met and is therefore imposed upon the effective date of the permit. Note that there is a two year delay to calculate the ADBAC. Potentially Dissolved Manganese - There were no data from the previous permit term regarding the presence/absence or quantification of this parameter in the discharge. A qualitative determination of RP has been made based on the facility type and size. Since the potential exists for this parameter to be present, monitoring has been added to the permit for future RP analysis.

Total Mercury (low level) – The RP analysis for mercury was based upon the NIL as described in the WQA. With the available data, the normal program was used to determine the appropriate statistics to determine the MEPC. The MEPC was greater than the MAPC and therefore limitations are required. Therefore a, 30-day average requirement has been added to the permit. Based upon previous monitoring the permittee may not be able to consistently meet this limitation and a compliance schedule has been added to the permit to give the permittee time to meet this limitation. The effluent limitation from the previous permit term has been included as an interim limitation. Total Recoverable Molybdenum - The RP analysis for total molybdenum was based upon the ADBAC as described in the WQA. With the available data the normal program was used to determine the appropriate statistics to determine the MEPC. The MEPC was less than the MAPC and therefore limitations are not necessary at this time, however monitoring will be required based on the facility type and size for future RP analysis. Therefore, a report only requirement has been added to the permit, effective immediately.

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Potentially Dissolved Nickel - There were no data from the previous permit term regarding the presence/absence or quantification of this parameter in the discharge. A qualitative determination of RP has been made based on the facility type and size. Since the potential exists for this parameter to be present, monitoring has been added to the permit for future RP analysis.

Potentially Dissolved Selenium - There were no data from the previous permit term regarding the presence/absence or quantification of this parameter in the discharge. A qualitative determination of RP has been made based on the facility type and size. Since the potential exists for this parameter to be present, monitoring has been added to the permit for future RP analysis.

Potentially Dissolved Silver - There were no data from the previous permit term regarding the presence/absence or quantification of this parameter in the discharge. A qualitative determination of RP has been made based on the facility type and size. Since the potential exists for this parameter to be present, monitoring has been added to the permit for future RP analysis.

Potentially Dissolved Zinc – The RP analysis for dissolved zinc was based upon the WQBEL as described in the WQA. With the available data the log-normal program was used to determine the appropriate statistics to determine the MEPC. The MEPC was greater than the MAPC and therefore limitations are required. Therefore a, 30-day average and daily maximum requirement has been added to the permit. The receiving stream has a TMDL for dissolved zinc, and although WLAs have not been established for this facility, the stream standards are implemented as the effluent limitations due to the impairment on the segment. Based upon previous monitoring, the permittee may not be able to consistently meet this limitation and a compliance schedule has been added to the permit to give the permittee time to meet this limitation. The maximum reported effluent concentration from the last 10 years of data is implemented in the interim. Sulfide - There were no data from the previous permit term regarding the presence/absence or quantification of this parameter in the discharge. A qualitative determination of RP has been made based on the facility type and size. Since the potential exists for this parameter to be present, monitoring has been added to the permit for future RP analysis. Nonylphenol - The RP analysis for nonylphenol was based upon the ADBAC as described in the WQA. Although all effluent data is below detection, the practical quantitation limit for nonylphenol (10µg/l) is greater than the ADBAC of 7.6 µg/l. Nonylphenol is a surfactant that is frequently found in domestic wastewater influent (e.g. detergents) and is partially removed through sorption to solids and separation of biosolids from wastewater. Therefore, a qualitative determination of reasonable potential has been made based on the size and type of the treatment facility to ensure that treatment is maintained, and a 2-year average limit is included in the permit. Previous monitoring as shown in Table VI-1 indicate that this limitation can be met and is therefore imposed upon the effective date of the permit. Note that although the effluent limitation is below the PQL, analytical results that are less than the PQL are compliant with the limitation. See the “Analytical and Sampling Methods for Monitoring and Reporting Section in Part I.D.5 of the permit for guidance on calculating averages and reporting analytical results that are less than the PQL. BTEX - A qualitative RP analysis was conducted as there no available data to conduct a quantitative RP analysis. Because benzene, toluene, ethylbenzene, and xylene could enter the collection system

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through I/I and the contaminated groundwater at VCUP site 131219-1 (Grand Tabor Hotel); therefore, limitations will be added to the permit. EPA’s Model NPDES Permit for Discharges Resulting From the Cleanup of Gasoline Released From Underground Storage Tanks (June 1989), recommends a total BTEX limit of 100 µg/l. Based on EPA’s model permit and the observed performance of control equipment at historical or existing cleanup sites, the Division is setting a BPJ based technology based limit for BTEX at 100 µg/l. This is a new limitation and it is unknown if the permittee can meet the limit and therefore a compliance schedule has been added to the permit to give the permittee time to meet this limitation. Report only is an interim limitation. Benzene - A qualitative RP analysis was conducted as there no available data to conduct a quantitative RP analysis. A qualitative determination of RP has been made because this parameter is present in fuel, and could enter the collection system via I/I and the contaminated groundwater at VCUP site 131219-1 (Grand Tabor Hotel). However since the WQBEL limitation is much lower than the technology-based numeric limitation for BTEX, Benzene will be report only. Organics – Other than nonylphenol, Benzene, and BTEX, the effluent is not expected or known to contain organic chemicals, and therefore, limitations for organic chemicals are not needed in this permit. Uranium - There were no data from the previous permit term regarding the presence/absence or quantification of this parameter in the discharge. A qualitative RP determination has been made because of geology, legacy land use and infiltration/inflow into the collection system noted in the submitted alternatives analysis (08/19/2019) and the potential for these parameters to be present in the groundwater surrounding the collection system. The Lake County Health Department provides radon testing information on its webpage. Uranium is part of the radon decay series. Monitoring has been added to the permit for this parameter for future RP analysis. Radium 226 & 228 – There were no data from the previous permit term regarding the presence/absence or quantification of this parameter in the discharge. A qualitative RP determination has been made because of geology, legacy land use and infiltration/inflow into the collection system noted in the submitted alternatives analysis (08/19/2019) and the potential for these parameters to be present in the groundwater surrounding the collection system. The Lake County Health Department provides radon testing information on its webpage. Radium 226 & 228 is part of the radon decay series. Monitoring has been added to the permit for this parameter for future RP analysis. Radionuclides - There were no data from the previous permit term regarding the presence/absence or quantification of the following parameters in the discharge. The permittee noted infiltration/inflow from groundwater into the collection system in the submitted alternatives analysis. Monitoring has been added to the permit for the parameters below for the division to make an RP determination. Even though the sampling frequency is quarterly, the division expects the permittee will rotate the sampling month to have monitoring results for all months by the end of the permit term.

Cesium 134, (pCi/l)

Strontium 90, (pCi/l)

Thorium 230 + Thorium 232, (pCi/l) Whole Effluent Toxicity (WET) Testing – Because California Gulch is not classified for aquatic life use,

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WET testing for stream segment COARUA06 was not considered. For this facility, acute WET testing has been determined to be applicable based on the instream waste concentrations calculated in the WQA for the downstream segment (COARUA02b). Because this is a major facility that may receive some industrial discharge, a qualitative determination of RP has been made. The permittee should read the WET testing section of Part I of the permit carefully, as this information has been updated in accordance with the Division’s updated policy, Implementation of the Narrative Standard for Toxicity in Discharge Permits Using Whole Effluent Toxicity (Sept 30, 2010). The permit outlines the test requirements and the required follow-up actions the permittee must take to resolve a toxicity incident. The permittee should also read the above mentioned policy which is available on the Permit Section website. The permittee should be aware that some of the conditions outlined above may be subject to change if the facility experiences a change in discharge, as outlined in Part II.A.2. of the permit. Such changes shall be reported to the Division immediately.

C. Parameter Speciation

For standards based upon the total and total recoverable methods of analysis, the limitations are based upon the same method as the standard.

For total recoverable arsenic, the analysis may be performed using a graphite furnace, however, this method may produce erroneous results and may not be available to the permittee. Therefore, the total method of analysis will be specified instead of the total recoverable method. An August 19, 1998 EPA memo states that the terms “total metals” and “total recoverable metals” are synonymous. Total metals and total recoverable metals are used to describe methods of hard mineral acid digestion.

Until recently there has not been an effective method for monitoring low-level total mercury concentrations in either the receiving stream or the facility effluent. With traditional methods, detection levels only as low as 0.2 ug/l have been consistently achieved, versus a total mercury limit of 0.04 ug/l. To ensure that adequate data are gathered to show compliance with the limitation and consistent with Division initiatives for mercury, quarterly effluent monitoring for total mercury at low-level detection methods will be required by the permit.

For metals with aquatic life-based dissolved standards, effluent limits and monitoring requirements are typically based upon the potentially dissolved method of analysis, as required under Regulation 31, Basic Standards and Methodologies for Surface Water. Thus, effluent limits and/or monitoring requirements for these metals will be prescribed as the “potentially dissolved” form.

For cyanide, the acute standard is in the form of "free" cyanide concentrations. Historically, analytical procedures were not readily available for measuring the concentration of free cyanide in a complex effluent therefore the Division required weak acid dissociable cyanide to be reported instead. Even though methods are now available to measure free cyanide, weak acid dissociable cyanide will be still required as this analytical procedure will detect free cyanide plus those forms of complex cyanide that are most readily converted to free cyanide. Therefore, ASTM (American Society for Testing and Materials) analytical procedure D2036-09, Method C, will be used to measure weak acid dissociable cyanide in the effluent.

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For total recoverable trivalent chromium, the regulations indicate that standard applies to the total of both the trivalent and hexavalent forms. Therefore, monitoring for total recoverable chromium will be required.

For hexavalent chromium, samples must be unacidified. Accordingly, dissolved concentrations will be measured rather than potentially dissolved concentrations.

VIII. ADDITIONAL TERMS AND CONDITIONS

A. Monitoring

Effluent Monitoring – Effluent monitoring will be required as shown in the permit document. Refer to the permit for locations of monitoring points. Monitoring requirements have been established in accordance with the frequencies and sample types set forth in the Baseline Monitoring Frequency, Sample Type, and Reduced Monitoring Frequency Policy for Industrial and Domestic Wastewater Treatment Facilities. This policy includes the methods for reduced monitoring frequencies based upon facility compliance as well as for considerations given in exchange for instream monitoring programs initiated by the permittee. Table VIII-1 shows the results of the reduced monitoring frequency analysis for Permitted Feature 001A, based upon compliance with the previous permit. Based upon the reduced monitoring frequency analysis for Permitted Feature 001A shown in Table VIII-1, the permittee is not eligible for reduced monitoring for ammonia, mercury, or dissolved zinc. The quarterly monitoring frequency for mercury is imposed consistent with the Divisions’ recent initiative to include quarterly monitoring for mercury because of the changes in analytical procedure that will allow total mercury to be quantified at much lower concentrations.

Table VIII-1 – Monitoring Reduction Evaluation

Parameter Proposed

Permit Limit

Average of 30-Day (or Daily Max)

Average Conc.

Standard Deviation

Long Term Characterization

(LTC)

Reduction Potential

pH (su) Minimum min 6.5 7.2 0.3 6.6 1 Level

pH (su) Maximum max 9.0 8.1 0.71 9.52

E. coli (#/100 ml) 630 27 23 73 3 Levels

TRC (mg/l) 0.34 0.13 0.066 0.262 1 Level

NH3 as N, Tot (mg/l) 13 9.2 5.9 21 None

BOD5, effluent (mg/l) 30 7.2 5.2 17.6 2 Levels

TSS, effluent (mg/l) 30 10 9.3 28.6 1 Level

Oil and Grease (mg/l) 10 0 0 0 3 Levels

Mo, TR (µg/l) 1150 0.00062 0.00018 0.00098 3 Levels

Hg, Tot (µg/l) 0.04 0.062 0.034 0.13 None

Zn, Dis (µg/l) 215 112 72 256 None

Nonylphenol (µg/l) 51 0 0 0 3 Levels

*Although oil & grease shows a 3-level reduction, this will not be applied. Since only visual observation is required for oil & grease, the permit frequency will be 5 days/week, which is the same frequency as the most frequently monitored parameter.

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B. Reporting

1. Discharge Monitoring Report – The Leadville Sanitation District facility must submit Discharge

Monitoring Reports (DMRs) on a monthly basis to the Division. These reports should contain the required summarization of the test results for all parameters and monitoring frequencies shown in Part I.A.2 of the permit. See the permit, Part I.D for details on such submission.

2. Additional Reporting – A reporting requirement has been included for an inflow/infiltration study.

3. Special Reports – Special reports are required in the event of an upset, bypass, or other

noncompliance. Please refer to Part II.A. of the permit for reporting requirements. As above, submittal of these reports to the US Environmental Protection Agency Region VIII is no longer required.

C. Signatory and Certification Requirements

Signatory and certification requirements for reports and submittals are discussed in Part I.D.8. of the permit.

D. Compliance Schedules

The following compliance schedules are included in the permit. As discussed in the Colorado WQCD Compliance Schedule Policy CW-3 and federal requirements, the Division evaluates the need for compliance schedules for discharges that are not new on the basis of what is necessary, appropriate, and whether the compliance schedule will achieve compliance with the underlying water quality based effluent limit “as soon as possible.” Necessary “Necessity” for a compliance schedule is determined on the basis of whether associated effluent limits can be met upon the effective date of the permit. A compliance schedule is necessary if there is information in the permit record that shows that the discharger cannot immediately comply with the underlying permit limits. A compliance schedule is only necessary if the effluent limitations are being added to the permit for the first time or if more stringent effluent limits are being added to a renewal permit based on a change in water quality standards. If water quality data exists to establish a level of water quality that can be achieved, then it is also necessary to establish an interim limit in the permit for the pollutant of concern. If data does not exist, then a report-only requirement should be included in the permit. A compliance schedule is not necessary if it is being proposed for a new discharger, if the compliance schedule is being issued to meet federal technology-based effluent limitation guidelines, or if a compliance schedule is based solely on the time needed to develop a use attainability analysis, site specific standard, alternatives analysis for antidegredation or a discharger specific variance.

The division has evaluated the necessity of a permit compliance schedule for each parameter in Section VI.B of this fact sheet. Based on this review, the division has determined that a compliance schedule for dissolved cadmium, total mercury, and dissolved zinc at outfall 001A is “necessary” as the permittee cannot meet the effluent limitations in the permit upon the effective date. For BTEX, effluent limits are being applied for the first time. For mercury, the previous limitation is established in the interim, and for dissolved zinc, an interim limitation is based on previous monitoring data. For dissolved cadmium and BTEX, there is no data to establish an interim limitation, so a reporting requirement has been added to the permit. Appropriate Once necessity has been determined, the Division evaluates the “appropriateness” of a compliance schedule. Factors relevant to whether a compliance schedule in a specific permit is “appropriate” under 40 C.F.R. § 122.47(a) include: how much time the discharger has already had to meet the WQBEL(s) under prior permits; the extent to which the discharger has made good faith efforts to comply with the WQBELs and other

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requirements in its prior permit(s); whether there is any need for modifications to treatment facilities, operations or measures to meet the WQBELs and if so, how long would it take to implement the modifications to treatment, operations or other measures; or whether the discharger would be expected to use the same treatment facilities, operations or other measures to meet the WQBEL as it would have used to meet the WQBEL in its prior permit. The compliance schedule proposed must be an enforceable sequence of events that contains milestones. If the compliance schedule lasts longer than one year, the milestones must be no more than one year apart and must describe how the compliance schedule will lead to compliance with the underlying permit limit at the end of the compliance schedule. The final effluent limits must contained in the permit and should be included at the end of the compliance schedule. In this case, the division has determined that the compliance schedule is appropriate. The discharger is being subject to the BTEX, dissolved cadmium, dissolved zinc, and more stringent mercury limits for the first time, and may need to make modifications to treatment facilities, operations or other measures in order to meet the new effluent limits. As soon as possible Once the Division determines that a compliance schedule is necessary and appropriate, the Division then uses information to develop a permit compliance schedule with enforceable milestones appropriate for the type of actions that are anticipated to be conducted to attain the underlying permit limits that ensure that compliance with the effluent limitations is achieved “as soon as possible.” In determining the duration of the compliance schedule to meet the underlying permit limits, the division intends to provide adequate time to conduct the actions needed leading to compliance with the limits, including the steps necessary to modify or install treatment facilities, retaining expertise, securing funding, characterizing sources, identifying control alternatives, and/or planning, designing and implementing the preferred alternative.

The division has evaluated the timelines for each parameter in the compliance schedule proposed in Part I.B.6 of the permit and has determined that the schedule will ensure compliance “as soon as possible.”

Two and a half years is an appropriate amount of time to retain expertise to characterize water quality, make changes to water quality treatment, or make adjustments to meet the underlying effluent limitations for dissolved cadmium, total mercury, dissolved zinc, and BTEX. The duration of the schedule until September 30, 2022 allows for time to collect the necessary data to determine whether the limitation can be met and to meet the final effluent limits. The following compliance schedules are included in the permit. See Part I.B of the permit for more information.

Activities to meet dissolved cadmium, total mercury, dissolved zinc, and BTEX final limits. The duration of the schedule was determined based on the time it is expected to take to characterize the effluent in future operational conditions to establish the level of reduction needed, to evaluate source control strategies, and if necessary, to implement in plant controls to reduce dissolved cadmium, total mercury, dissolved zinc, and BTEX.

E. Stormwater

Pursuant to 5 CCR 1002-61.3(2), wastewater treatment facilities with a design flow of 1.0 mgd or more, or that are required to have an approved pretreatment program, are specifically required to obtain stormwater discharge permit coverage or a Stormwater No Exposure Certification, in order to discharge stormwater from their facilities to state waters. The stormwater discharge permit applicable to wasterwater treatment facilities is the CDPS General Permit for Stormwater Discharges Associated with Non-Extractive Industrial Activity. Division records indicate that Leadville Sanitation District applied for and obtained coverage under a Stormwater No Exposure Certification for the Leadville Sanitation District. The No Exposure Certification number is CONOX0111.

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F. Additional Permit Requirements

The Use of the Pretreatment Framework to identify, characterize, and control sources of pollutants to POTWs

The Division reviewed the pretreatment framework and its implementation in Colorado, and determined that this framework is the most appropriate tool to identify, characterize, and control sources of pollutants to the POTW. The Division reviewed both the Leadville SD WWTF permit provisions, and the Division’s standard permit provisions to ensure that the requirements are equivalent to those provided by EPA (EPA implements the federal pretreatment program in Colorado because the state has not been delegated its own pretreatment program). Permit provisions differ for POTWs required to maintain a pretreatment program and for POTWs not required to maintain a pretreatment program. The Division found that the provisions for POTWs that are required to maintain a pretreatment program met these requirements, and therefore there is no need to change these provisions in Colorado’s permits.These POTWs are required to identify and locate all possible industrial users (“IUs”), identify the character and volume of pollutants, maintain current information regarding IUs and conduct periodic pollutant scans of both influent and effluent for a list of parameters. The permit provisions also conformed to those provided by EPA for inclusion in Division issued permits.

POTWs not required to maintain a pretreatment program are not held to this level of requirement, and as such are less likely to generate the level of information described in the statement of basis and purpose. These POTWs are required to submit information in their permit applications regarding industrial discharges. EPA as the pretreatment authority also notifies POTWs without pretreatment programs to conduct a comprehensive industrial user survey, as needed, to further evaluate these POTWs for development of a program. EPA also recommends that permits for all POTWs require periodic pollutant scans of effluent, require periodic pollutant scans of effluent.

EPA has provided the following permit language for POTWs without approved programs.

The Permittee shall sample and analyze the effluent for the following pollutants:

Total Arsenic Total Nickel Total Cadmium Total Selenium Total Chromium Total Silver Total Copper Total Zinc Total Lead Total Cyanide Total Mercury Total Phenols Total Molybdenum

The sampling shall commence within thirty (30) days of the effective date of this permit and continue at the following frequency: Sampling Schedule for Non-Approved Programs: Majors (above 1 MGD) 1 per year

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G. Economic Reasonableness Evaluation Section 25-8-503(8) of the revised (June 1985) Colorado Water Quality Control Act required the

Division to "determine whether or not any or all of the water quality standard based effluent limitations are reasonably related to the economic, environmental, public health and energy impacts to the public and affected persons, and are in furtherance of the policies set forth in sections 25-8-192 and 25-8-104."

The Colorado Discharge Permit System Regulations, Regulation No. 61, further define this requirement under 61.11 and state: "Where economic, environmental, public health and energy impacts to the public and affected persons have been considered in the classifications and standards setting process, permits written to meet the standards may be presumed to have taken into consideration economic factors unless:

a. A new permit is issued where the discharge was not in existence at the time of the

classification and standards rulemaking, or

b. In the case of a continuing discharge, additional information or factors have emerged that were not anticipated or considered at the time of the classification and standards rulemaking."

The evaluation for this permit shows that the Water Quality Control Commission, during their proceedings to adopt the Classifications and Numeric Standards for Arkansas River Basin, considered economic reasonableness. Furthermore, this is not a new discharger and no new information has been presented regarding the classifications and standards. Therefore, the water quality standard-based effluent limitations of this permit are determined to be reasonably related to the economic, environmental, public health and energy impacts to the public and affected persons and are in furtherance of the policies set forth in Sections 25-8-102 and 104. If the permittee disagrees with this finding, pursuant to 61.11(b)(ii) of the Colorado Discharge Permit System Regulations, the permittee should submit all pertinent information to the Division during the public notice period.

H. Opportunities for public comment, public meetings, and administrative adjudication

1. Opportunity to Submit Public Comment on the Draft Permit

Interested persons may submit written comments to the Division on this draft permit and fact sheet during the term of the public comment period. Note that if you do not identify an issue in your comments on the draft permit, you may not be allowed to raise that issue in an administrative adjudication.

2. Opportunity to Request an Extension to the Public Comment Period

Interested persons may also request an extension of the comment period. This should be a stand-alone request via email or letter to the permit writer during the duration of the public comment period. The request should include specific reasons why the extension is needed.

3. Opportunity to Request a Responsive Public Comment Period

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Interested persons may also request a responsive period of public comment in which any person may file a written response to the material filed by any other person during the comment period. This should be a stand-alone request via email or letter to the permit writer during the duration of the public comment period or within 10 days of the close of the public comment period. If the division grants a responsive comment period, there will also be a 10-day rebuttal period immediately following the close of the deadline for responsive comments. Filing of rebuttal comments is optional.

4. Opportunity to Request a Public Meeting

Interested persons, states, agencies, and groups may request a public meeting on the terms of the draft permit in accordance with 61.5(3). This should be a stand-alone request via email or letter to the permit writer during the duration of the public comment period. The request should discuss the degree of public interest regarding the draft, including the reasons why a public meeting is warranted. The Division shall hold a meeting if there is a significant degree of public interest.

5. Opportunity for Administrative Adjudication

Once the final permit is issued, the applicant or any other person affected or aggrieved by the Division's final determination may request an adjudicatory hearing within thirty (30) calendar days of the date of issuance, under 5 CCR 1002-61 (Colorado Discharge Permit System Regulations), Regulation 61.7. Any request must comply with the Water Quality Control Act, 24-4-101, C.R.S., et seq. and the Water Quality Control Commission’s regulations, including Regulation 61.7 and 5 CCR 1002-21 (Procedural Rules), Regulation 21.4(B). Failure to contest any term and condition of the permit in this request for an adjudicatory hearing constitutes consent to the condition by the permittee.

6. Opportunity to Request a Stay of Terms and Conditions of Final Permit

If an applicant for a renewal permit files a request for an administrative hearing in accordance with section 24-4-105, C.R.S., the applicant may also request that the Division stay the contested terms and conditions of the renewal permit. This request must be made within thirty (30) days of issuance of the final permit.

IX. REFERENCES

A. Colorado Department of Public Health and Environment, Water Quality Control Division Files, for Permit Number CO0021164.

B. “Design Criteria Considered in the Review of Wastewater Treatment Facilities”, Policy 96-1, Colorado

Department of Public Health and Environment, Water Quality Control Commission, April 2007. C. Basic Standards and Methodologies for Surface Water, Regulation No. 31, Colorado Department of

Public Health and Environment, Water Quality Control Commission, effective January 31, 2018. D. Classifications and Numeric Standards for Arkansas River Basin, Regulation No. 32, Colorado

Department of Public Health and Environment, Water Quality Control Commission, effective December 31, 2018.

E. Colorado Discharge Permit System Regulations, Regulation No. 61, Colorado Department of Public

Health and Environment, Water Quality Control Commission, effective December 31, 2018.

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F. Regulations for Effluent Limitations, Regulation No. 62, Colorado Department of Public Health and

Environment, Water Quality Control Commission, effective July 30, 2012. G. Pretreatment Regulations, Regulation No. 63, Colorado Department of Public Health and

Environment, Water Quality Control Commission, effective March 1, 2017. H. Biosolids Regulation, Regulation No. 64, Colorado Department of Public Health and Environment,

Water Quality Control Commission, effective June 30, 2014. I. Colorado River Salinity Standards, Regulation No. 39, Colorado Department of Public Health and

Environment, Water Quality Control Commission, effective May 9, 2007.

J. Section 303(d) List of Water Quality Limited Segments Requiring TMDLs, Regulation No 93, Colorado Department of Public Health and Environment, Water Quality Control Commission, effective March 2, 2018.

K. Colorado’s Section 303(d) List of Impaired Waters and Monitoring and Evaluation List, Regulation No

93, Colorado Department of Public Health and Environment, Water Quality Control Commission, effective March 2, 2018.

L. Antidegradation Significance Determination for New or Increased Water Quality Impacts, Procedural Guidance, Colorado Department of Public Health and Environment, Water Quality Control Division, effective December 2001.

M. Memorandum Re: First Update to (Antidegradation) Guidance Version 1.0, Colorado Department of

Public Health and Environment, Water Quality Control Division, effective April 23, 2002.

N. Determination of the Requirement to Include Water Quality Standards-Based Limits in CDPS Permits Based on Reasonable Potential, Policy Number CW-1, Colorado Department of Public Health and Environment, Water Quality Control Division, effective November 18, 2013.

O. The Colorado Mixing Zone Implementation Guidance, Colorado Department of Public Health and

Environment, Water Quality Control Division, effective April 2002.

P. Baseline Monitoring Frequency, Sample Type, and Reduced Monitoring Frequency Policy for Domestic and Industrial Wastewater Treatment Facilities, Water Quality Control Division Policy WQP-20, May 1, 2007.

Q. Implementing Narrative Standards in Discharge Permits for the Protection of Irrigated Crops, Water

Quality Control Division Policy WQP-24, March 10, 2008.

R. Implementing Narrative Standard for Toxicity in Discharge Permits Using Whole Effluent Toxicity (WET) Testing. Colorado Department of Public Health and Environment, Water Quality Control Division Policy Permits-1, September 30, 2010.

S. Policy for Conducting Assessments for Implementation of Temperature Standards in Discharge Permits, Colorado Department of Public Health and Environment, Water Quality Control Division, Policy Number WQP-23, effective July 3, 2008.

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T. Permit Compliance Schedules, Colorado Department Public Health and Environment, Water Quality Control Division Policy Number CW-3, effective March 4, 2014.

U. Procedural Regulations for Site Applications for Domestic Wastewater Treatment Works, Regulation No. 22, Colorado Department of Public Health and Environment, Water Quality Control Commission, effective September 30, 2009.

V. Regulation Controlling Discharges to Storm Sewers, Regulation No. 65, Colorado Department of Public

Health and Environment, Water Quality Control Commission, effective May 30, 2008.

W. Water and Wastewater Facility Operator Certification Requirements, Regulation No. 100, Colorado Department of Public Health and Environment, Water Quality Control Commission, effective August 31, 2017.

X. Total Maximum Daily Load Assessment for the Arkansas River/Lake Creek/Chalk Creek/ Evans Gulch/Lake/Chaffee County, Colorado. Colorado Department of Public Health and Environment, Water Quality Control Commission, effective July 14, 2009.

X. ATTACHMENTS

Attachment 1: Draft Water Quality Assessment for California Gulch – COARUA06 (February 13, 2020). Attachment 2: Proposed Determination on the Low-Level Mercury Treatment Alternatives Analysis for the Leadville Sanitation District WWTF (February 13, 2020)

XI. PUBLIC NOTICE COMMENTS

FOR DIVISION USE ONLY

G04 Sewage Sludge/Biosolids Annual Program Reports

G07 Pretreatment Program Reports

G09 Sewer Overflow/Bypass Event Reports

G3A DMRs: Regular Submission Frequency

G8B SIU Compliance Reports (State is Control Authority)

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Dedicated to protecting and improving the health and environment of the people of Colorado


Attachment 1

Water Quality Assessment California Gulch and the Arkansas River

Leadville Sanitation District WWTF Christine Wehner February 13, 2020

Table of Contents

I. WATER QUALITY ASSESSMENT SUMMARY.......................................................................................................................... 2 II. INTRODUCTION ........................................................................................................................................................ 2 III. WATER QUALITY STANDARDS ....................................................................................................................................... 4

Narrative Standards ................................................................................................................................................. 4 Standards for Organic Parameters and Radionuclides ...................................................................................... 4 Temperature ............................................................................................................................................................. 5 Segment Specific Numeric Standard ..................................................................................................................... 6 Table Value Standards and Hardness Calculations ............................................................................................ 7 Total Maximum Daily Loads and Regulation 93 – Colorado’s Section 303(d) List of Impaired Waters and Monitoring and Evaluation List ...................................................................................................................... 9

IV. RECEIVING STREAM INFORMATION ............................................................................................................................... 10 Low Flow Analysis .................................................................................................................................................. 10 Mixing Zones ........................................................................................................................................................... 11 Ambient Water Quality ......................................................................................................................................... 12

V. FACILITY INFORMATION AND POLLUTANTS EVALUATED ................................................................................................ 13 Facility Information ............................................................................................................................................... 13 Pollutants of Concern ............................................................................................................................................ 14

VI. DETERMINATION OF WATER QUALITY BASED EFFLUENT LIMITATIONS (WQBELS) ........................................................... 15 Technical Information ........................................................................................................................................... 15 Calculation of WQBELs .......................................................................................................................................... 16 Whole Effluent Toxicity (WET) Testing: ............................................................................................................ 20

VII. ANTIDEGRADATION EVALUATION ................................................................................................................................. 20 Introduction to the Antidegradation Process.................................................................................................... 21 Significance Tests for Temporary Impacts and Dilution ................................................................................. 21 New or Increased Impact and Non Impact Limitations (NILs) ........................................................................ 22 Calculation of Loadings for New or Increased Impact Test ............................................................................ 23 Determination of Baseline Water Quality (BWQ) ............................................................................................. 25 Bioaccumulative Significance Test ...................................................................................................................... 27 Significant Concentration Threshold .................................................................................................................. 27 Determination of the Antidegradation Based Average Concentrations ....................................................... 27 Concentration Significance Tests ........................................................................................................................ 28 Antidegradation Based Effluent Limitations (ADBELs).................................................................................... 29 Alternatives Analysis ............................................................................................................................................. 30

VIII. TECHNOLOGY BASED LIMITATIONS ........................................................................................................................ 30 Federal Effluent Limitation Guidelines ............................................................................................................. 30 Regulations for Effluent Limitations .................................................................................................................. 30 Nutrient Effluent Limitation Considerations .................................................................................................... 31 Supplemental Reg. 85 Nutrient Monitoring ...................................................................................................... 32

IX. REFERENCES .............................................................................................................................................................. 32

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Water Quality Assessment

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I. Water Quality Assessment Summary Table A-1 includes summary information related to this WQA. This summary table includes key regulatory starting points used in development of the WQA such as: receiving stream information; threatened and endangered species; 303(d) and Monitoring and Evaluation listings; low flow and facility flow summaries; and a list of parameters evaluated.

Table A-1 WQA Summary

Facility Information

Facility Name Permit Number Design Flow

(max 30-day ave, MGD)

Design Flow (max 30-day ave,

CFS)

Leadville Sanitation District CO0021164 1.15 1.8

Receiving Stream Information

Receiving Stream Name Segment ID Designation Classification(s)

S1. California Gulch COARUA06 Undesignated Recreation Class N Agriculture

S2. Arkansas River COARUA02b Undesignated* Aquatic Life Cold 1 Recreation Class E Agriculture

Low Flows (cfs)

Receiving Stream Name 1E3 (1-day)

7E3 (7-day)

30E3 (30-day)

Ratio of 30E3 to the Design Flow (cfs)

S1. California Gulch 0 0 0 0:1

S2. Arkansas River 9.5 10 12 7:1

Regulatory Information

T&E Species

303(d) (Reg 93)

Monitor and Eval (Reg 93)

Existing TMDL Temporary

Modification(s) Control

Regulation

No None None COARUA02b:

Cd(Dis), Zn(Dis) 07/14/2009

None Regulation 85

Pollutants Evaluated

Ammonia, E. Coli, TRC, Nitrate, Metals, Nonylphenol, Temperature, Nutrients, Radionuclides, Uranium, BTEX

*Designation: 9/30/00 Base-line does not apply; January 2014 Base-line will apply instead. II. Introduction The water quality assessment (WQA) of California Gulch and the Arkansas River near the Leadville Sanitation District Wastewater Treatment Facility (WWTF), located in Lake County, is intended to determine the assimilative capacities available for pollutants found to be of concern. This WQA describes how the water quality based effluent limits (WQBELs) are developed. These parameters may or may not appear in the permit with limitations or monitoring requirements, subject to other determinations such as reasonable

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potential analysis, evaluation of federal effluent limitation guidelines, implementation of state-based technology based limits, mixing zone analyses, 303(d) listings, threatened and endangered species listing, or other requirements as discussed in the permit rationale. Evaluation of stormwater-only outfalls is not included in this WQA. These outfalls are subject to the applicable water quality standards and Federal ELGs for this industry type. Permit requirements and discussion regarding these outfalls are provided in the permit and fact sheet. Figure A-1 contains a map of the study area evaluated as part of this WQA.

FIGURE A-1

The Leadville Sanitation District WWTF discharges to California Gulch, which is stream segment COARUA06. This means the Arkansas River Basin, Upper Arkansas Sub-basin, Stream Segment 06. This segment is composed of the “Mainstem of California Gulch, including all tributaries, from the source to the confluence with the Arkansas River. Mainstem of St. Kevin's Gulch from the source to the confluence with Tennessee Creek.”. Stream segment COARUA06 is classified for Recreation Class N and Agriculture. Due to the proximity to other segments, the Arkansas River, which is stream segment COARUA02b, was also considered. This means the Arkansas River Basin, Upper Arkansas Sub-basin, Stream Segment 02b. This segment is composed of the “Mainstem of the Arkansas River from a point immediately above California Gulch to a point immediately above the confluence with Lake Fork”. Stream segment COARUA02b is classified for Aquatic Life Cold 1, Recreation Class E, and Agriculture.

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This area of Colorado has been heavily mined in the past, and California Gulch is on the National Priorities list (NPL) for potential future clean-up under the Superfund program. California Gulch flows approximately 1.25 miles from the point of discharge of the Leadville Sanitation District WWTF to the Arkansas River, which has a TMDL for dissolved cadmium and dissolved zinc. In order to be protective of downstream water quality, the Arkansas River has been included in this water quality assessment. Information used in this assessment includes data gathered from the Leadville Sanitation District WWTF, the Division, the Colorado Division of Water Resources (DWR), Riverwatch, the U.S. Environmental Protection Agency (EPA), the U.S. Geological Survey (USGS), the U.S. Census Bureau and communications with the local water commissioner. The data used in the assessment consist of the best information available at the time of preparation of this WQA analysis. III. Water Quality Standards Narrative Standards Narrative Statewide Basic Standards have been developed in Section 31.11(1) of the regulations, and apply to any pollutant of concern, even where there is no numeric standard for that pollutant. Waters of the state shall be free from substances attributable to human-caused point source or nonpoint source discharges in amounts, concentrations or combinations which: for all surface waters except wetlands; (i) can settle to form bottom deposits detrimental to the beneficial uses. Depositions are stream bottom buildup of materials which include but are not limited to anaerobic sludge, mine slurry or tailings, silt, or mud; or (ii) form floating debris, scum, or other surface materials sufficient to harm existing beneficial uses; or (iii) produce color, odor, or other conditions in such a degree as to create a nuisance or harm existing beneficial uses or impart any undesirable taste to significant edible aquatic species or to the water; or (iv) are harmful to the beneficial uses or toxic to humans, animals, plants, or aquatic life; or (v) produce a predominance of undesirable aquatic life; or (vi) cause a film on the surface or produce a deposit on shorelines; and for surface waters in wetlands; (i) produce color, odor, changes in pH, or other conditions in such a degree as to create a nuisance or harm water quality dependent functions or impart any undesirable taste to significant edible aquatic species of the wetland; or (ii) are toxic to humans, animals, plants, or aquatic life of the wetland. In order to protect the Basic Standards in waters of the state, effluent limitations and/or monitoring requirements for any parameter of concern could be put in CDPS discharge permits. Standards for Organic Parameters and Radionuclides Radionuclides: Statewide Basic Standards have been developed in Section 31.11(2) and (3) of The Basic Standards and Methodologies for Surface Water to protect the waters of the state from radionuclides and organic chemicals. In no case shall radioactive materials in surface waters be increased by any cause attributable to municipal, industrial, or agricultural practices or discharges to as to exceed the following levels, unless alternative site-specific standards have been adopted. Standards for radionuclides are shown in Table A-2.

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Table A-2 Radionuclide Standards

Parameter Picocuries per Liter

Americium 241* 0.15

Cesium 134 80

Plutonium 239, and 240* 0.15

Radium 226 and 228* 5

Strontium 90* 8

Thorium 230 and 232* 60

Tritium 20,000

*Samples for these materials should be analyzed using unfiltered (total) samples. These Human Health based standards are 30-day average values.

Organics: The organic pollutant standards contained in the Basic Standards for Organic Chemicals Table are applicable to all surface waters of the state for the corresponding use classifications, unless alternative site-specific standards have been adopted. These standards have been adopted as “interim standards” and will remain in effect until alternative permanent standards are adopted by the Commission. These interim standards shall not be considered final or permanent standards subject to antibacksliding or downgrading restrictions. Although not reproduced in this WQA, the specific standards for organic chemicals can be found in Regulation 31.11(3). In order to protect the Basic Standards in waters of the state, effluent limitations and/or monitoring requirements for radionuclides, organics, or any other parameter of concern could be put in CDPS discharge permits. The aquatic life standards for organics apply to all stream segments that are classified for aquatic life. The water supply standards apply only to those segments that are classified for water supply. The water + fish standards apply to those segments that have a Class 1 aquatic life and a water supply classification. The fish ingestion standards apply to Class 1 aquatic life segments that do not have a water supply designation. The water + fish and the fish ingestion standards may also apply to Class 2 aquatic life segments, where the Water Quality Control Commission has made such determination. Because the California Gulch is not classified for water supply or aquatic life, these standards do not apply to this discharge. Because the Arkansas River is classified for Aquatic Life Cold 1, without a water supply designation, the fish ingestion and aquatic life standards apply to this discharge. Nutrients Phosphorus and Total Inorganic Nitrogen: Regulation 85, the Nutrients Management Control Regulation has been adopted by the Water Quality Control Commission and became effective September 30, 2012. This regulation contains requirements for phosphorus and Total Inorganic Nitrogen (TIN) concentrations for some point source dischargers. Limitations for phosphorus and TIN may be applied in accordance with this regulation. Temperature Temperature shall maintain a normal pattern of diurnal and seasonal fluctuations with no abrupt changes and shall have no increase in temperature of a magnitude, rate, and duration deemed deleterious to the

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resident aquatic life. This standard shall not be interpreted or applied in a manner inconsistent with section 25-8-104, C.R.S. Segment Specific Numeric Standards Numeric standards are developed on a basin-specific basis and are adopted for particular stream segments by the Water Quality Control Commission. The standards in Table A-3a have been assigned to stream segment COARUA06, and the standards in Table A-3b have been assigned to stream segment COARUA02b in accordance with the Classifications and Numeric Standards for Arkansas River Basin. Additionally, the parameters in Table A-3c are also being evaluated as they are parameters of concern for this facility type. These parameters are being included based on the numeric standards in Regulation 31.

Table A-3a

In-stream Standards for Stream Segment COARUA06

Physical and Biological

E. coli chronic = 630 colonies/100 ml

Metals

Uranium acute and chronic = varies*

*Uranium standard varies based on site specific conditions, as described in Regulation 32.5(3).

Table A-3b

In-stream Standards for Stream Segment COARUA02b

Physical and Biological

Dissolved Oxygen (DO) = 6 mg/l, minimum (7 mg/l, minimum during spawning)

pH 6.5- 9.0

E. coli chronic = 126 colonies/100 ml

Temperature June-Sept = 17° C MWAT and 21.7° C DM

Temperature Oct-May = 9° C MWAT and 13° C DM

Inorganic

Total Ammonia acute and chronic = TVS

Chlorine acute = 0.019 mg/l

Chlorine chronic = 0.011 mg/l

Free Cyanide acute = 0.005 mg/l

Sulfide chronic = 0.002 mg/l

Boron chronic = 0.75 mg/l

Nitrite acute = 0.05 mg/l

Nitrate acute = 100 mg/l

Metals

Dissolved Arsenic acute = 340 µg/l

Total Recoverable Arsenic chronic = 7.6 µg/l

Dissolved Cadmium acute and chronic = SSE1

Total Recoverable Trivalent Chromium chronic = 100 µg/l

Dissolved Trivalent Chromium acute and chronic = TVS

Dissolved Hexavalent Chromium acute and chronic = TVS

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Dissolved Copper acute and chronic = TVS

Total Recoverable Iron chronic = 1000 µg/l

Dissolved Lead acute and chronic = TVS

Dissolved Manganese acute and chronic = TVS

Total Recoverable Molybdenum chronic = 150 µg/l

Total Mercury chronic = 0.01 µg/l

Dissolved Nickel acute and chronic = TVS

Dissolved Selenium acute and chronic = TVS

Dissolved Silver acute and Dissolved Silver chronic for trout = TVS

Uranium acute and chronic = varies2

Dissolved Zinc acute and chronic = SSE3

1 Site specific equations for dissolved cadmium are as follows: Cadmium(acute) = e^(0.9789*ln(hardness)-3.866)*(1.136672-(ln(hardness)*0.041838)) Cadmium(chronic) = (1.101672-(ln(hardness)*0.041838))*(e^(0.7998*ln(hardness)- 3.1725))

2 Uranium standard varies based on site specific conditions, as described in Regulation 32.5(3):

(b) Uranium levels in surface waters shall be maintained at the lowest practicable level. (c) In no case shall uranium levels in waters assigned a water supply classification be increased by any cause attributable to municipal, industrial, or agricultural discharges so as to exceed 16.8-30 µg/l or naturally-occurring concentrations (as determined by the State of Colorado), whichever is greater.

3 Site specific equations for dissolved zinc are as follows: Zinc(acute) = 0.978*e^(0.8537(ln(hardness))+2.2178) Zinc(chronic) = 0.986*e^(0.8537(ln(hardness))+2.0469)

Table A-3c

Additional Standards Being Evaluated Based on Regulation 31 for Segment COARUA02b

Organics*

Nonylphenol acute = 28 µg/l

Nonylphenol chronic = 6.6 µg/l

Benzene chronic = 51 µg/l

Benzene acute = 5300 µg/l

Ethylbenzene chronic = 2100 µg/l

Ethylbenzene acute = 32000 µg/l

Toluene chronic = 5900 µg/l

Toluene acute = 17500 µg/l

*Because segment COARUA02b is not classified for water supply, organic standards being evaluated from Regulation 31 are based on aquatic life-based and fish ingestion standards.

Table Value Standards and Hardness Calculations As metals with standards specified as TVS are not included as standards for stream segment COARUA06, the hardness value of this receiving water and the subsequent calculation of the TVS equations is inconsequential and is therefore omitted from this WQA. However, the hardness value of and the subsequent calculation of the TVS equations are calculated below for stream segment COARUA02b. Standards for metals are generally shown in the regulations as Table Value Standards (TVS), and these often must be derived from equations that depend on the receiving stream hardness or species of fish present; for ammonia, standards are discussed further in Section IV of this WQA. The Classification and Numeric Standards documents for each basin include a specification for appropriate hardness values to be used. Specifically, the regulations state that:

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The hardness values used in calculating the appropriate metal standard should be based on the lower 95% confidence limit of the mean hardness value at the periodic low flow criteria as determined from a regression analysis of site-specific data. Where insufficient site-specific data exists to define the mean hardness value at the periodic low flow criteria, representative regional data shall be used to perform the regression analysis. Where a regression analysis is not appropriate, a site-specific method should be used.

Hardness data for Arkansas River near the point of discharge of the Leadville Sanitation District WWTF were insufficient to conduct a regression analysis based on the low flow. Therefore, the Division’s alternative approach to calculating hardness was used, which involves computing a mean hardness. For cadmium and zinc, the minimum of the average hardness for each month was chosen in lieu of the average hardness for the whole year due to the TMDL on the segment. For this TMDL, average hardness was calculated for each month, and for this WQA, the minimum monthly average hardness is chosen to be protective of stream water quality year-round. The mean hardness for June was computed to be 50 mg/l based on sampling data from WQCD Station 7182 (Arkansas River below Leadville) located on the Arkansas River 6.5 miles downstream from the Leadville Sanitation District. Data were available from this site from June 2014 through June 2018. This hardness value and the formulas contained in the TVS were used to calculate the in-stream water quality standards for cadmium and zinc, with the results shown in Table A-4a.

Table A-4a

TVS-Based Metals Water Quality Standards for CO0021164 for the Arkansas River Based on the Table Value Standards Contained in the Colorado Department of Public Health and

Environment Water Quality Control Commission Regulation 32

Parameter In-Stream Water Quality Standard

TVS Formula: Hardness (mg/l) as CaCO3 = 50

Cadmium, Dissolved Acute 0.94 µg/l [1.136672-0.041838ln(hardness)]e

(0.9789(ln(hardness))-3.866)

Chronic 0.9 µg/l [1.101672-0.041838ln(hardness)]e(0.7998(ln(hardness))-3.1725)

Zinc, Dissolved Acute 253 µg/l 0.978e(0.8537(ln(hardness))+2.2178)

Chronic 215 µg/l 0.986 e(0.8537(ln(hardness))+2.0469)

For all other metals, the mean hardness was computed to be 88 mg/l based on sampling data from WQCD Station 7182 (Arkansas River below Leadville) located on the Arkansas River 6.5 miles downstream from the Leadville Sanitation District. Data were available from this site from August 2009 through June 2018. This hardness value and the formulas contained in the TVS were used to calculate the in-stream water quality standards for metals, with the results shown in Table A-4b. DRAFT


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Table A-4b

TVS-Based Metals Water Quality Standards for CO0021164 for the Arkansas River Based on the Table Value Standards Contained in the Colorado Department of Public Health and

Environment Water Quality Control Commission Regulation 32

Parameter In-Stream Water Quality Standard

TVS Formula: Hardness (mg/l) as CaCO3 = 88

Trivalent Chromium, Dissolved

Acute 511 µg/l e(0.819(ln(hardness))+2.5736)

Chronic 67 µg/l e(0.819(ln(hardness))+0.5340)

Hexavalent Chromium, Dissolved

Acute 16 µg/l Numeric standards provided, formula not applicable

Chronic 11 µg/l Numeric standards provided, formula not applicable

Copper, Dissolved Acute 12 µg/l e(0.9422(ln(hardness))-1.7408)

Chronic 8.0 µg/l e(0.8545(ln(hardness))-1.7428)

Lead, Dissolved Acute 56 µg/l [1.46203-0.145712ln(hardness)][e

(1.273(ln(hardness))-1.46)]

Chronic 2.2 µg/l [1.46203-0.145712ln(hardness)][e(1.273(ln(hardness))-4.705)]

Manganese, Dissolved

Acute 2857 µg/l e(0.3331(ln(hardness))+6.4676)


Nickel, Dissolved Acute 419 µg/l e(0.846(ln(hardness))+2.253)


Selenium, Dissolved

Acute 18.4 µg/l Numeric standards provided, formula not applicable

Chronic 4.6 µg/l Numeric standards provided, formula not applicable

Silver, Dissolved Acute 1.6 µg/l ½ e(1.72(ln(hardness))-6.52)

Chronic 0.06 µg/l e(1.72(ln(hardness))-10.51)

Total Maximum Daily Loads and Regulation 93 – Colorado’s Section 303(d) List of Impaired Waters and Monitoring and Evaluation List Stream segment COARUA06 is not listed on the Division’s 303(d) list of water quality impacted streams and is not on the monitoring and evaluation list. The Division’s Restoration and Protection Unit have completed the TMDL for dissolved cadmium and dissolved zinc, and therefore the requirements of this TMDL apply for these parameters. However, this TMDL did not set WLAs for the Leadville SD WWTF because it discharges to California Gulch, which is on the National Priorities List (NPL) for potential future clean-up under the Superfund program. A determination was made that WLAs would not be appropriate at this time, since any WLAs might unduly influence California Gulch clean up goals and since the Leadville SD WWTF appears not to be the cause of metals exceedances in California Gulch. Since this stream is impaired for dissolved cadmium and dissolved zinc, but no WLAs are assigned to this facility, the permit limits will be set to the water quality standards.

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IV. Receiving Stream Information Low Flow Analysis The Colorado Regulations specify the use of low flow conditions when establishing water quality based effluent limitations, specifically the acute and chronic low flows. The acute low flow, referred to as 1E3, represents the one-day low flow recurring in a three-year interval, and is used in developing limitations based on an acute standard. The 7-day average low flow, 7E3, represents the seven-day average low flow recurring in a 3 year interval, and is used in developing limitations based on a Maximum Weekly Average Temperature standard (MWAT). The chronic low flow, 30E3, represents the 30-day average low flow recurring in a three-year interval, and is used in developing limitations based on a chronic standard. California Gulch (COARUA06) Although there is flow in California Gulch upstream of the Leadville Sanitation District WWTF, the 1E3 and 30E3 monthly low flows are set at zero based on information provided by the local Water Commissioner.

There is little if any natural flow during low flow conditions, and low flows are largely dependent on effluent from the EPA California Gulch-Yak Tunnel WWTF. This determination that during periods of low flow, most or all of the flow in California Gulch is contributed by the Yak Tunnel WWTF effluent, is well established and has been a part of the permit record since the 2000 Water Quality Analysis. In accordance with Division standard procedures, when the 1E3, 7E3, and 30E3 monthly low flows are driven entirely by a nearby discharge, the low flows available to the facility are set at zero. For this analysis, low flows are summarized in Table A-5a.

Table A-5a

Low Flows for California Gulch at the Leadville Sanitation District WWTF

Low Flow (cfs)

Annual Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

1E3 Acute

0 0 0 0 0 0 0 0 0 0 0 0 0

7E3 Chronic

0 0 0 0 0 0 0 0 0 0 0 0 0

30E3 Chronic

0 0 0 0 0 0 0 0 0 0 0 0 0

The ratio of the low flow of California Gulch to the Leadville Sanitation District WWTF design flow is 0:1. Note that since the low flow has been determined to be zero, the ambient water quality discussion for this segment is unnecessary and has therefore been deleted in this WQA. This is explained in more detail under the Technical Information discussion in Section VI. Arkansas River (COARUA02b) To determine the low flows available to the Leadville Sanitation District WWTF, USGS gage station 07081200 (Arkansas River near Leadville, CO) was used. This flow gage provides a representative measurement of the upstream flow because there are no diversions or confluence of significance between the flow gage and the confluence with California Gulch. Daily flows from the USGS Gage Station 07081200 (Arkansas River near Leadville, CO) were obtained and the annual 1E3 and 30E3 low flows were calculated using U.S. Environmental Protection Agency (EPA) DFLOW software. The output from DFLOW provides calculated acute and chronic low flows for each month.

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Flow data from October 1, 2000 through September 30, 2018 were available from the gage station. The gage station and time frames were deemed the most accurate and representative of current flows and were therefore used in this analysis. Based on the low flow analysis described previously, the upstream low flows available to the Leadville Sanitation District WWTF were calculated and are presented in Table A-5b.

Table A-5b

Low Flows for the Arkansas River upstream of California Gulch

Low Flow (cfs)

Annual Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

1E3 Acute

9.5 9.6 11 11 12 16 23 13 9.5 9.5 14 15 11

7E3 Chronic

10 10 10 11 12 16 23 13 10 10 14 15 11

30E3 Chronic

12 12 12 12 12 16 23 13 12 12 14 15 12

During the months of April, May, June, July, October, and November, the acute low flow calculated by DFLOW exceeded the chronic low flow. In accordance with Division standard procedures, the acute low flow was thus set equal to the chronic low flow for these months. The ratio of the low flow of California Gulch to the Leadville Sanitation District WWTF design flow is 7:1. Mixing Zones The amount of the available assimilative capacity (dilution) that may be used by the permittee for the purposes of calculating the WQBELs may be limited in a permitting action based upon a mixing zone analysis or other factor. These other factors that may reduce the amount of assimilative capacity available in a permit are: presence of other dischargers in the vicinity; the presence of a water diversion downstream of the discharge (in the mixing zone); the need to provide a zone of passage for aquatic life; the likelihood of bioaccumulation of toxins in fish or wildlife; habitat considerations such as fish spawning or nursery areas; the presence of threatened and endangered species; potential for human exposure through drinking water or recreation; the possibility that aquatic life will be attracted to the effluent plume; the potential for adverse effects on groundwater; and the toxicity or persistence of the substance discharged. Unless a facility has performed a mixing zone study during the course of the previous permit, and a decision has been made regarding the amount of the assimilative capacity that can be used by the facility, the Division assumes that the full assimilative capacity can be allocated. Note that the review of mixing study considerations, exemptions and perhaps performing a new mixing study (due to changes in low flow, change in facility design flow, channel geomorphology or other reason) is evaluated in every permit and permit renewal. If a mixing zone study has been performed and a decision regarding the amount of available assimilative capacity has been made, the Division may calculate the water quality based effluent limitations (WQBELs) based on this available capacity. In addition, the amount of assimilative capacity may be reduced by T&E implications.

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Since the receiving stream has a zero low flow as calculated above, the WQBELs would be equal to the WQS, and therefore consideration of full or reduced assimilative capacity is inconsequential. Ambient Water Quality California Gulch (COARUA06) The Division evaluates ambient water quality based on a variety of statistical methods as prescribed in Section 31.8(2)(a)(i) and 31.8(2)(b)(i)(B) of the Colorado Department of Public Health and Environment Water Quality Control Commission Regulation No. 31, and as outlined in the Division’s Policy for Characterizing Ambient Water Quality for Use in Determining Water Quality Standards Based Effluent Limits (WQP-19). The ambient water quality was not assessed for California Gulch because the background in-stream low flow condition is zero. Arkansas River (COARUA02b) Ambient water quality is evaluated in this WQA analysis for use in determining assimilative capacities and in completing antidegradation reviews for pollutants of concern, where applicable. To conduct an assessment of the ambient water quality on the Arkansas River upstream of California Gulch and the Leadville SD WWTF, data for arsenic, cadmium, chromium, copper, iron, lead, manganese, nickel, silver, selenium, and zinc were gathered from station AR-3B, located immediately downstream of the confluence of the Arkansas River and California Gulch. Data were available for a period of record from May 2001 through September 2005. For E. Coli, ammonia, molybdenum, and mercury, data were gathered from WQCD station 7182 (Arkansas River below Leadville), located approximately 6.5 miles downstream of the facility. Data were available for a period of record of March 2009 through June 2018 for all parameters except mercury, which were available for January 2000 through May 2001. Note that for E. Coli and ammonia, which are not shared pollutants of concern with the Yak Tunnel discharge, there were no data available upstream of the confluence with California Gulch. Although these data are based on samples collected at downstream locations, they are comparable to data representative of upstream water quality. In lieu of modeling the Yak Tunnel WWTF along with the Leadville SD WWTF, data based on samples collected at downstream locations were used as ambient data in order to incorporate the effect of this discharge on the water quality of the Arkansas River. A summary of these data is presented in Error! Reference source not found..

Table A-6

Ambient Water Quality for Arkansas River

Parameter Number

of Samples

15th Percentile

50th Percentile

85th Percentile

Mean Maximum

Chronic Stream

Standard Notes

E. coli (#/100 ml) 5 1 1 20 3 44 126 1, 2

NH3 as N, Tot (mg/l) 29 0.015 0.025 0.039 0.034 0.27 TVS

NH3 as N, Tot (mg/l) Jan 1 0.038 0.038 0.038 0.038 0.038 TVS

NH3 as N, Tot (mg/l) Feb 3 0.019 0.023 0.024 0.022 0.025 TVS

NH3 as N, Tot (mg/l) Mar 3 0.018 0.026 0.034 0.026 0.037 TVS

NH3 as N, Tot (mg/l) Apr 4 0.017 0.029 0.041 0.029 0.045 TVS

NH3 as N, Tot (mg/l) May 3 0 0 0.022 0.011 0.032 TVS 2

NH3 as N, Tot (mg/l) Jun 4 0 0.0085 0.021 0.01 0.024 TVS 2

NH3 as N, Tot (mg/l) Jul 3 0.002 0.0067 0.017 0.0092 0.021 TVS

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NH3 as N, Tot (mg/l) Aug 5 0.012 0.024 0.03 0.021 0.033 TVS

NH3 as N, Tot (mg/l) Sep 1 0.039 0.039 0.039 0.039 0.039 TVS

NH3 as N, Tot (mg/l) Oct 6 0 0.007 0.087 0.052 0.27 TVS 2

NH3 as N, Tot (mg/l) Nov 3 0 0 0.013 0.0063 0.019 TVS 2

NH3 as N, Tot (mg/l) Dec 4 0.02 0.038 0.043 0.032 0.046 TVS

As, TR (µg/l) 19 0 0 0.65 0.39 3 7.6 2

As, Dis (µg/l) 24 0 0 1.9 0.63 5 340 2

Cd, TR (µg/l) 19 0.5 1 3.1 1.7 6.6 NA

Cd, Dis (µg/l) 34 0.23 0.52 1.5 0.97 5.9 0.90 3

Cr, Dis (µg/l) 3 1.5 5 5 3.3 5 NA

Cu, Dis (µg/l) 34 0 0 2.1 1.5 13 8.0 2

Fe, TR (µg/l) 19 125 570 1294 757 2800 1000

Pb, TR (µg/l) 19 1.5 7.4 25 21 200 NA

Pb, Dis (µg/l) 34 0 0.49 0.88 1.1 11 2.20 2

Mn, Dis (µg/l) 24 20 88 476 209 1060 1578

Mo, TR (µg/l) 24 0 0 0 3.9 47 150 2

Hg, Tot (µg/l) 12 0 0 0 0 0 0.01 2

Ni, Dis (µg/l) 3 6 20 20 13 20 46

Se, Dis (µg/l) 3 5.3 18 18 12 18 4.6 3

Ag, Dis (µg/l) 20 0 0 0.3 0.54 5 0.06 2, 3

Zn, Dis (µg/l) 34 75 143 471 264 1270 215 3

Note 1: The calculated mean is the geometric mean. Note that for summarization purposes, the value of one was used where there was no detectable amount because the geometric mean cannot be calculated using a value equal to zero.

Note 2: When sample results were below detection levels, the value of zero was used in accordance with the Division's standard approach for summarization and averaging purposes.

Note 3: The ambient water quality exceeds the water quality standards for these parameters.

V. Facility Information and Pollutants Evaluated Facility Information The Leadville Sanitation District WWTF is located at in the SW 1/4 of the SW 1/4 of S27, T9S, R80W; 13867 US Highway 24 S in Leadville CO 80461; at 39.22911° latitude North and 106.3297°longitude West in Lake County. The current design capacity of the facility is 1.15 MGD (1.8 cfs). Wastewater treatment is accomplished using a mechanical wastewater treatment process. The technical analyses that follow include assessments of the assimilative capacity based on this design capacity. An assessment of Division records indicate that there are 7 facilities discharging to the same stream segment or other stream segments immediately upstream or downstream from this facility. Several of these facilities are covered by general permits and have limitations set at the water quality standards. These facilities were not modeled in this WQA as they have a minimal impact on the ambient water quality. Other facilities were located more than twenty miles from the Leadville Sanitation District WWTF and thus were not considered. The nearest dischargers were:

Mountain View Villages WWTF (CO0048372) discharges to Tennessee Creek, which then flows to the Arkansas River, 3 miles upstream of the facility with a design flow of 0.1 MGD.

Mountain Valley Estates WWTF (CO0049021) discharges to the East Fork of the Arkansas River, which flows into the Arkansas River, 3 miles upstream of the facility, with a design flow of 0.02 MGD.

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Moose Haven Condominium WWTF (CO0047279) discharges to Box Creek, which then flows to the Arkansas River, approximately 10 miles downstream of the proposed facility with a design flow of 0.01 MGD.

California Gulch – Yak Tunnel WWTF discharges to California Gulch, 3 miles upstream of the Leadville Sanitation District WWTF. According to the 2013 WQA, the California Gulch-Yak Tunnel WWTF has a design flow of 1.5 MGD.

California Gulch (COARUA06) Due to the in-stream low flow of zero, the assimilative capacities during times of low flow are not affected by nearby contributions. Therefore, modeling nearby facilities in conjunction with this facility was not necessary for stream segment COARUA06. Arkansas River (COARUA02b) Due to its proximity, the California Gulch – Yak Tunnel WWTF was considered in this water quality analysis. Assimilative capacity for the stream was not divided between these two facilities. The contribution of the California Gulch – Yak Tunnel WWTF was taken into account for shared pollutants of concern, as downstream Arkansas River data was used as upstream ambient water quality for metals in Segment COARUA02b. Pollutants of Concern Pollutants of concern may be determined by one or more of the following: facility type; effluent characteristics and chemistry; effluent water quality data; receiving water quality; presence of federal effluent limitation guidelines; or other information. Parameters evaluated in this WQA may or may not appear in a permit with limitations or monitoring requirements, subject to other determinations such as a reasonable potential analysis, mixing zone analyses, 303(d) listings, threatened and endangered species listings or other requirement as discussed in a permit rationale. There are no site-specific in-stream water quality standards for BOD5 or CBOD5, TSS, percent removal, and oil and grease for this receiving stream. Thus, assimilative capacities were not determined for these parameters. The applicable limitations for these pollutants can be found in Regulation No. 62 and will be applied in the permit for the WWTF. The following parameters were identified by the Division as pollutants to be evaluated for this facility:

Total Residual Chlorine

E. coli

Nitrate

Ammonia

Temperature

Metals and Cyanide

Nonylphenol

Radionuclides

Uranium

BTEX Organic chemicals (BTEX) listed in Section III of this WQA are potential pollutants of concern for the Leadville Sanitation District WWTF due to the documented inflow/infiltration into the collection system and the presence of VCUP Site 131219-1 (Grand Tabor Hotel), which is a former gasoline station that may result in the contribution of gasoline and diesel products to the soils and groundwater. It is the Division’s standard procedure to consider metals and cyanide as potential pollutants of concern for all major domestic WWTFs.

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Neither receiving stream is classified as a water supply, so water supply standards will not apply to this discharge. Note that segment COARUA02b is assigned an agricultural use classification and a 100 mg/l nitrate standard will be applied to this discharge. During assessment of the facility, nearby facilities, and receiving stream water quality, no additional parameters were identified as pollutants of concern. VI. Determination of Water Quality Based Effluent Limitations (WQBELs) Technical Information Note that the WQBELs developed in the following paragraphs, are calculations of what an effluent limitation may be in a permit. The WQBELs for any given parameter, will be compared to other potential limitations (federal effluent limitations guidelines, state effluent limitations, or other applicable limitation) and typically the more stringent limit is incorporated into a permit. If the WQBEL is the more stringent limitation, incorporation into a permit is dependent upon a reasonable potential analysis. In-stream background data and low flows evaluated in Sections II and III are used to determine the assimilative capacity of California Gulch near the Leadville Sanitation District WWTF for pollutants of concern, and to calculate the WQBELs. For all parameters except ammonia, it is the Division’s approach to calculate the WQBELs using the lowest of the monthly low flows (referred to as the annual low flow) as determined in the low flow analysis. For ammonia, it is the standard procedure of the Division to determine monthly WQBELs using the monthly low flows, as the regulations allow the use of seasonal flows. The Division’s standard analysis consists of steady-state, mass-balance calculations for most pollutants and modeling for pollutants such as ammonia. The mass-balance equation is used by the Division to calculate the WQBELs, and accounts for the upstream concentration of a pollutant at the existing quality, critical low flow (minimal dilution), effluent flow and the water quality standard. The mass-balance equation is expressed as:

2

11332

Q

QMQMM

Where,

Q1 = Upstream low flow (1E3 or 30E3) Q2 = Average daily effluent flow (design capacity for domestic wastewater treatment facilities) Q3 = Downstream flow (Q1 + Q2) M1 = In-stream background pollutant concentrations at the existing quality M2 = Calculated WQBEL M3 = Water Quality Standard, or other maximum allowable pollutant concentration

When Q1 equals zero, Q2 equals Q3, and the following results:

32 MM

Because the low flow (Q1) for California Gulch is zero, the WQBELs for California Gulch for the pollutants of concern are equal to the in-stream water quality standards. A more detailed discussion of the technical analysis is provided in the pages that follow. The upstream background pollutant concentrations used in the mass-balance equation will vary based on the regulatory definition of existing ambient water quality. For most pollutants, existing quality is determined to be the 85th percentile. For metals in the total or total recoverable form, existing quality is determined to be the 50th percentile. For pathogens such as fecal coliform and E. coli, existing quality is determined to be the geometric mean.

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For temperature, the highest 7-day mean (for the chronic standard) of daily average stream temperature, over a seven consecutive day period will be used in calculations of the chronic temperature assimilative capacity, where the daily average temperature should be calculated from a minimum of three measurements spaced equally through the day. The highest 2-hour mean (for the acute standard) of stream temperature will be used in calculations of the acute temperature assimilative capacity. The highest 2-hour mean should be calculated from a minimum of 12 measurements spaced equally through the day. Because the two facilities are in close proximity, they must be modeled together for shared parameters of concern. When facilities are modeled together, the design flow, Q2, reflects the combined design flow of the facilities modeled together for a particular parameter, thereby resulting in the calculation of the WQBELs, M2, applicable to the modeled facilities as set forth below. Calculation of WQBELs Using the mass-balance equation provided in the beginning of Section VI, the acute and chronic low flows set out in Section IV, ambient water quality as discussed in Section IV, and the in-stream standards shown in Section III, the WQBELs were calculated. The data used and the resulting WQBELs, M2, are set forth in Table A-7a for the chronic WQBELs and A-7b for the acute WQBELs. Where a WQBEL is calculated to be a negative number and interpreted to be zero or the ambient water quality exceeds the in-stream standard, the Division standard procedure is to allocate the water quality standard to prevent further degradation of the receiving waters. Chlorine: There are no point sources discharging total residual chlorine within one mile of the Leadville Sanitation District WWTF. Because chlorine is rapidly oxidized, in-stream levels of residual chlorine are detected only for a short distance below a source. Ambient chlorine was therefore assumed to be zero. Based on a 2002 chlorine decay study conducted by Leadville Sanitation District, chlorine levels in California Gulch just above the Arkansas River were found to be no more than 25% of the effluent chlorine concentrations observed at the discharge point from Leadville SD WWTF. Therefore, at this time, the Division concluded the WQBELS for chlorine to be four times the limit calculated for the Arkansas River. E. coli: There are no point sources discharging E. coli within one mile of the Leadville Sanitation District WWTF. Thus, WQBELs were evaluated separately. For E. coli, the Division establishes the 7-day geometric mean limit as two times the 30-day geometric mean WQBEL and also includes maximum limits of 2,000 colonies per 100 ml (30-day geometric mean) and 4,000 colonies per 100 ml (7-day geometric mean). This 2000 colony limitation also applies to discharges to ditches. Temperature: California Gulch (COARUA06) is not classified for aquatic use, and therefore, there are no temperature standards assigned to this segment. Therefore, temperature is not further assessed in this WQA. Uranium Range: Because dissolved uranium assimilative capacities are calculated based on a range of standards, The Basic Standards and Methodologies for Surface Water requires further evaluation. Specifically, the regulations state that “Control requirements, such as discharge permit effluent limitations, shall be established using the first number in the range as the ambient water quality target, provided that no effluent limitation shall require an “end-of-pipe” discharge level more restrictive than the second number in the range.” Because the WQBEL for dissolved uranium has been calculated to be less than the second number in the range of standards, the second standard (as shown in Table A-3b, footnote 2) would instead be substituted as the WQBEL pursuant to the regulations. Radionuclides: Limitations for radionuclides are implemented based on the standards in Regulation 31, which are applicable to all surface waters, including California Gulch. Due to the lack of dilution in California Gulch, the WQBELs are set equal to the water quality standard, and calculating WQBELs in the Arkansas River is not necessary.

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BTEX: Limitations for BTEX are implemented based on the standards in Regulation 31 (Table A-3b), which are applicable to the Arkansas River. There was no ambient water quality data for organic chemicals of concern for the Leadville SD WWTF. To calculate WQBELs, a value of 0 was used for ambient water quality.

Table A-7a

Chronic WQBELs for California Gulch (COARUA06)

Parameter Q1 (cfs) Q2 (cfs) Q3 (cfs) M1 M3 M2

E. coli (#/100 ml) 0 1.8 1.8 1 630 630

U, Dis (µg/l) 0 1.8 1.8 NA 16.8-30 30*

Cesium 134 (pCi/l) 0 1.8 1.8 NA 80 80

Radium 226 and 228 (pCi/l)

0 1.8 1.8 NA 5 5

Strontium 90 (pCi/l)

0 1.8 1.8 NA 8 8

Thorium 230 and 232 (pCi/l)

0 1.8 1.8 NA 60 60

*No “end-of-pipe” effluent limitation shall be more restrictive than the second number in the range in

accordance with Regulation 32.3(c). Therefore, the WQBEL is 30 µg/l.

Table A-7b

Acute WQBELs for California Gulch (COARUA06)


E. coli (#/100 ml) chronic X 2 = acute 1260

Table A-7c

Chronic WQBELs for Arkansas River (COARUA02b)


E. coli (#/100 ml) 12 1.8 13.8 3 126 947

TRC (mg/l) 12 1.8 13.8 0 0.011 0.34¹

As, TR (µg/l) 12 1.8 13.8 0 7.6 58

Cd, Dis (µg/l) 12 1.8 13.8 1.5 0.9 0.9²

Cr+3, TR (µg/l) 12 1.8 13.8 0 100 767

Cr+3, Dis (µg/l) 12 1.8 13.8 0 67 514

Cr+6, Dis (µg/l) 12 1.8 13.8 0 11 84

Cu, Dis (µg/l) 12 1.8 13.8 2.1 8.0 47

Fe, TR (µg/l) 12 1.8 13.8 570 1000 3867

Pb, Dis (µg/l) 12 1.8 13.8 0.88 2.2 11

Mn, Dis (µg/l) 12 1.8 13.8 476 1578 8925

Mo, TR (µg/l) 12 1.8 13.8 0 150 1150

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Hg, Tot (µg/l) 12 1.8 13.8 0 0.01 0.077

Ni, Dis (µg/l) 12 1.8 13.8 20 46 219

Se, Dis (µg/l) 12 1.8 13.8 18 4.6 4.6²

Ag, Dis (µg/l) 12 1.8 13.8 0.3 0.06 0.06²

Zn, Dis (µg/l) 12 1.8 13.8 471 215 215²

Sulfide as H2S (mg/l) 12 1.8 13.8 12 0.002 0.015

Nonylphenol (µg/l) 12 1.8 13.8 0 6.6 51

Benzene (µg/l) 12 1.8 13.8 0 51 391

Ethylbenzene (µg/l) 12 1.8 13.8 0 2100 16100

Toluene (µg/l) 12 1.8 13.8 0 5900 45233

¹WQBEL for TRC was multiplied by 4, as described in the text.

²The existing water quality for this parameter exceeds the water quality standard; see the text for further discussion.

Table A-7d

Acute WQBELs for Arkansas River (COARUA02b)


E. coli (#/100 ml) chronic X 2 = acute 1894

TRC (mg/l) 9.5 1.8 11.3 0 0.019 0.48¹

As, Dis (µg/l) 9.5 1.8 11.3 1.9 340 2124

Cd, Dis (µg/l) 9.5 1.8 11.3 1.5 0.94 0.94²

Cr+3, Dis (µg/l) 9.5 1.8 11.3 0 511 3208

Cr+6, Dis (µg/l) 9.5 1.8 11.3 0 16 100

Cu, Dis (µg/l) 9.5 1.8 11.3 2.1 12 64

CN, Free (µg/l) 9.5 1.8 11.3 0 5 31

Pb, Dis (µg/l) 9.5 1.8 11.3 0.88 56 347

Mn, Dis (µg/l) 9.5 1.8 11.3 476 2857 15423

Ni, Dis (µg/l) 9.5 1.8 11.3 20 419 2525

Se, Dis (µg/l) 9.5 1.8 11.3 18 18.4 21

Ag, Dis (µg/l) 9.5 1.8 11.3 0.3 1.6 8.5

Zn, Dis (µg/l) 9.5 1.8 11.3 471 253 253²

Nonylphenol (µg/l) 9.5 1.8 11.3 0 28 176

Benzene (µg/l) 9.5 1.8 11.3 0 5300 33272

Ethylbenzene (µg/l)

9.5 1.8 11.3 0 32000 200889

Toluene (µg/l) 9.5 1.8 11.3 0 17500 109861

¹WQBEL for TRC was multiplied by 4, as described in the text.

²The existing water quality for this parameter exceeds the water quality standard; see the text for further discussion.

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Ammonia: The Ammonia Toxicity Model (AMMTOX) is a software program designed to project the downstream effects of ammonia and the ammonia assimilative capacities available to each discharger based on upstream water quality and effluent discharges. To develop data for the AMMTOX model, an in-stream water quality study should be conducted of the upstream receiving water conditions, particularly the pH and corresponding temperature, over a period of at least one year. Effluent pH data were available from the Leadville Sanitation District WWTF and were used to establish the average facility pH contributions in the AMMTOX model. There were no pH or temperature data available for the Arkansas River or temperature data for the Leadville Sanitation District WWTF that could be used as adequate input data for the AMMTOX model. Therefore, the Division standard procedure is to rely on statistically-based, regionalized data for pH and temperature compiled from similar facilities and receiving waters. Upstream ammonia data for each month, as summarized in Table A-6 were available, and were used as inputs to the AMMTOX model. Note that because California Gulch, the immediate receiving water, does not have any ammonia standards, only the Arkansas River is considered in the AMMTOX model. The AMMTOX model may be calibrated for a number of variables in addition to the data discussed above. The values used for the other variables in the model are listed below:

Stream velocity = 0.3Q0.4d

Default ammonia loss rate = 6/day

pH amplitude was assumed to be medium

Default times for pH maximum, temperature maximum, and time of day of occurrence

pH rebound was set at the default value of 0.2 su per mile

Temperature rebound was set at the default value of 0.7 degrees C per mile. The results of the ammonia analyses for the Leadville Sanitation District WWTF are presented in Table A-8.

Table A-8

AMMTOX Results for California Gulch at the Leadville Sanitation District WWTF

Design of 1.15 MGD (1.8 cfs)

Month Total Ammonia Chronic (mg/l) Total Ammonia Acute (mg/l)

January 13 23

February 20 37

March 17 31

April 17 32

May 24 44

June 45 65*

July 37 65*

August 34 65*

September 29 62

October 24 46

November 17 32

December 13 23

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*Ammonia effluent limitation is capped at 65 mg/l per Division practice. Whole Effluent Toxicity (WET) Testing: The Water Quality Control Division has established the use of WET testing as a method for identifying and controlling toxic discharges from wastewater treatment facilities. WET testing is being utilized as a means to ensure that there are no discharges of pollutants "in amounts, concentrations or combinations which are harmful to the beneficial uses or toxic to humans, animals, plants, or aquatic life" as required by Section 31.11 (1) of the Basic Standards and Methodologies for Surface Waters. The requirements for WET testing are being implemented in accordance with Division policy, Implementation of the Narrative Standard for Toxicity in Discharge Permits Using Whole Effluent Toxicity (Sept 30, 2010). Note that this policy has recently been updated and the permittee should refer to this document for additional information regarding WET. In-Stream Waste Concentration (IWC) – Where monitoring or limitations for WET are deemed appropriate by the Division, the chronic in-stream dilution is critical in determining whether acute or chronic conditions shall apply. In accordance with Division policy, for those discharges where the chronic IWC is greater than 9.1% and the receiving stream has a Class 1 Aquatic Life use or Class 2 Aquatic Life use with all of the appropriate aquatic life numeric standards, chronic conditions will normally apply. Where the chronic IWC is less than or equal to 9.1, or the stream is not classified as described above, acute conditions will normally apply. The chronic IWC is determined using the following equation:

IWC = [Facility Flow (FF)/(Stream Chronic Low Flow (annual) + FF)] X 100%

The flows and corresponding IWC for the appropriate discharge point are:

Permitted Feature Chronic Low Flow, 30E3 (cfs)

Facility Design Flow (cfs)

IWC, (%)

001A – COARUA02b

12

1.8

7

Because California Gulch is not classified for aquatic life use, the IWC for stream segment COARUA06 was not calculated. The IWC for the Arkansas River (COARUA02b) is 7%, which represents a wastewater concentration of 7 % effluent to 93% receiving stream. This IWC correlates to acute WET testing. The fact sheet and the permit will contain additional information regarding the type of WET testing applicable to this facility. VII. Antidegradation Evaluation As set out in The Basic Standards and Methodologies for Surface Water, Section 31.8(2)(b), an antidegradation analysis is required except in cases where the receiving water is designated as “Use Protected.” Note that “Use Protected” waters are waters “that the Commission has determined do not warrant the special protection provided by the outstanding waters designation or the antidegradation review process” as set out in Section 31.8(2)(b). The antidegradation section of the regulation became effective in December 2000, and therefore antidegradation considerations are applicable to this WQA analysis. California Gulch (COARUA06) According to the Classifications and Numeric Standards for Arkansas River Basin, stream segment COARUA06 is Undesignated. Thus, an antidegradation review is required for this segment if new or increased impacts are found to occur.

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Arkansas River (COARUA02b) According to the Classifications and Numeric Standards for Arkansas River Basin, stream segment COARUA06 is Undesignated. Thus, an antidegradation review is required for this segment if new or increased impacts are found to occur. Introduction to the Antidegradation Process The antidegradation process conducted as part of this water quality assessment is designed to determine if an antidegradation review is necessary and if necessary, to complete the required calculations to determine the limits that can be selected as the antidegradation-based effluent limit (ADBEL), absent further analyses that must be conducted by the facility. As outlined in the Antidegradation Significance Determination for New or Increased Water Quality Impacts, Procedural Guidance (AD Guidance), the first consideration of an antidegradation evaluation is to determine if new or increased impacts are expected to occur. This is determined by a comparison of the newly calculated WQBELs verses the existing permit limitations in place as of September 30, 2000, and is described in more detail in the analysis. Note that the AD Guidance refers to the permit limitations as of September 30, 2000 as the existing limits. However, segment COARUA02b has a special qualifier that requires the baseline to be determined at the time of the first new or increased water quality impact (Classifications and Numeric Standards for Arkansas River Basin, 32.40). Thus, the September 30, 2000 date does not apply to this antidegradation review. The first new or increased water quality impact occurred prior to the first permit renewal following the addition of this provision (January 2014), and limits that existed prior to that renewal were used to determine NILs. If a new or increased impact is found to occur, then the next step of the antidegradation process is to go through the significance determination tests. These tests include: 1) bioaccumulative toxic pollutant test; 2) temporary impacts test; 3) dilution test (100:1 dilution at low flow) and; 4) a concentration test. As the determination of new or increased impacts, and the bioaccumulative and concentration significance determination tests require more extensive calculations, the Division will begin the antidegradation evaluation with the dilution and temporary impact significance determination tests. These two significance tests may exempt a facility from further AD review without the additional calculations. Note that the antidegradation requirements outlined in The Basic Standards and Methodologies for Surface Water specify that chronic numeric standards should be used in the antidegradation review; however, where there is only an acute standard, the acute standard should be used. The appropriate standards are used in the following antidegradation analysis. Significance Tests for Temporary Impacts and Dilution California Gulch (COARUA06) The ratio of the chronic (30E3) low flow to the design flow is 0:1, and is less than the 100:1 significance criteria. Therefore this facility is not exempt from an AD evaluation based on the dilution significance determination test, and the AD evaluation must continue. Arkansas River (COARUA02b) The ratio of the chronic (30E3) low flow to the design flow is 7:1, and is less than the 100:1 significance criteria. Therefore this facility is not exempt from an AD evaluation based on the dilution significance determination test, and the AD evaluation must continue. For the determination of a new or increased impact and for the remaining significance determination tests, additional calculations are necessary. Therefore, at this point in the antidegradation evaluation, the Division will go back to the new or increased impacts test. If there is a new or increased impact, the last two significance tests will be evaluated.

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New or Increased Impact and Non Impact Limitations (NILs) To determine if there is a new or increased impact to the receiving water, a comparison of the new WQBEL concentrations and loadings verses the concentrations and loadings as of September 30, 2000 (or January 2014 for COARUA02b), needs to occur. If either the new concentration or loading is greater than the September 2000 (or January 2014) concentration or loading, then a new or increased impact is determined. If this is a new facility (commencement of discharge after September 30, 2000/January 2014) it is automatically considered a new or increased impact. Note that the AD Guidance document includes a step in the New or Increased Impact Test that calculates the Non-Impact Limit (NIL). The permittee may choose to retain a NIL if certain conditions are met, and therefore the AD evaluation for that parameter would be complete. As the NIL is typically greater than the ADBAC, and is therefore the chosen limit, the Division will typically conclude the AD evaluation after determining the NIL. Where the NILs are very stringent, or upon request of a permittee, the Division will calculate both the NIL and the AD limitation so that the limitations can be compared and the permittee can determine which of the two limits they would prefer, one which does not allow any increased impact (NIL), or the other which allows an insignificant impact (AD limit). The non impact limit (NIL) is defined as the limit which results in no increased water quality impact (no increase in load or limit over the September 2000 or January 2014 load or limit). The NIL is calculated as the September 2000/January 2014 loading, divided by the new design flow, and divided by a conversion factor of 8.34. If there is no change in design flow, then the NIL is equal to the September 2000 or January 2014 permit limitation. If the facility was in place, but did not have a limitation for a particular parameter in the September 2000 permit, the Division may substitute an implicit limitation. Consistent with the First Update to the AD Guidance of April 2002, an implicit limit is determined based on the approach that specifies that the implicit limit is the maximum concentration of the effluent from October 1998 to September 2000. If this data is unavailable, the Division may substitute more recent representative data, if appropriate, on a case by case basis. Note that the AD requirements specify that chronic values should be used in the AD review; however, where there is only an acute standard, the acute value should be used. Thus, for determining implicit limitations for chronic standards, the 30 day average effluent values are used, while for acute standards, the daily maximum values are used. Note that if there is a change in design flow, the implicit limit/loading is subject to recalculation based on the new design flow. For parameters that are undisclosed by the permittee, and unknown to the Division to be present, an implicit limitation may not be recognized. This facility was in place as a discharger prior to September 30, 2000 and January 28, 2014, and therefore the new or increased impacts test must be conducted. As the design flow for this facility is the same as it was in September 2000 (and January 2014), the NILs are equal to the permit limitations as of September 2000 (and January 2014). California Gulch (COARUA06) For E. Coli, the limitations as of September 2000 were used in the evaluation of new or increased impacts. In accordance with the Division’s practice regarding E. coli, an implicit limit for E. coli is determined as 0.32 times the permit limit for fecal coliform. For radionuclides and uranium, there are no effluent data available and therefore, the Division will include monitoring requirements in the permit so that data can be collected in order to make such a determination of an implicit limit. Arkansas River (COARUA02b) For E. Coli, total residual chlorine, and total ammonia, the limitations as of January 2014 were used in the evaluation of new or increased impacts. For total arsenic, dissolved cadmium, cyanide, dissolved copper, total iron, dissolved lead, total molybdenum, dissolved manganese (aquatic life), total mercury, dissolved nickel, dissolved selenium,

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dissolved silver, and dissolved zinc, data from this timeframe (June 2012 – December 2013) were used to determine an implicit limitation. For nonylphenol, data prior to January 2014 were not available. Therefore data from March 2014 through December 2015 were determined to be adequate and were used to determine the implicit limitations. For dissolved arsenic, dissolved trivalent chromium, total recoverable trivalent chromium, dissolved hexavalent chromium, sulfide, and BTEX there are no effluent data available and therefore, the Division will include monitoring requirements in the permit so that data can be collected in order to make such a determination of an implicit limit. Calculation of Loadings for New or Increased Impact Test The equations for the loading calculations are given below. Note that the AD requirements outlined in The Basic Standards and Methodologies for Surface Water specify that chronic numeric standards should be used in the AD review; however, where there is only an acute standard, the acute standard should be used. Thus, the chronic low flows will be used later in this AD evaluation for all parameters with a chronic standard, and the acute low flows will be used for those parameters with only an acute standard.

Previous permit load = Mpermitted (mg/l) × Qpermitted (mgd) × 8.34 New WQBELs load = M2 (mg/l) × Q2 (mgd) × 8.34

Where,

Mpermitted = September 2000 permit limit (or implicit limit) (mg/l) Qpermitted = design flow as of September 2000 (mgd) Q2 = current design flow (same as used in the WQBEL calculations) M2 = new WQBEL concentration (mg/l) 8.34 = unit conversion factor

Table A-9a and 9b show the results of these calculations and the determination of a new or increased impact.

Table A-9a

Determination of New or Increased Impacts for California Gulch (COARUA06)

Pollutant Sept 2000

Permit Limit

Sept 2000 Permit Load

(lbs/day) NIL

New WQBEL

New WQBEL Load

(lbs/day)

New or Increased

Impact

E. coli (#/100 ml) 928 8900 928 630 6042 No

As shown in Table A-9a, there are no new or increased impacts to the receiving stream based on the new WQBELS, and therefore the AD evaluation is complete, and AD limitations are not necessary. The WQBELs are the final result of this WQA.

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Table A-9b

Determination of New or Increased Impacts for the Arkansas River (COARUA02b)

Pollutant

January 2014

Permit Limit

January 2014

Permit Load

(lbs/day)

NIL New

WQBEL New WQBEL

Load (lbs/day)

New or Increased

Impact

E. coli (#/100 ml) 1277 12248 1277 947 9083 No

TRC (mg/l) 0.34 3.3 0.34 0.34 3.3 No

NH3, Tot as N (mg/l), Jan 20 192 20 13 125 No

NH3, Tot as N (mg/l), Feb 20 192 20 20 192 No

NH3, Tot as N (mg/l) Mar 20 192 20 17 163 No

NH3, Tot as N (mg/l) Apr 20 192 20 17 163 No

NH3, Tot as N (mg/l) May 20 192 20 24 230 Yes

NH3, Tot as N (mg/l) Jun 20 192 20 45 432 Yes

NH3, Tot as N (mg/l) Jul 20 192 20 37 355 Yes

NH3, Tot as N (mg/l) Aug 20 192 20 34 326 Yes

NH3, Tot as N (mg/l) Sep 20 192 20 29 278 Yes

NH3, Tot as N (mg/l) Oct 20 192 20 24 230 Yes

NH3, Tot as N (mg/l) Nov 20 192 20 17 163 No

NH3, Tot as N (mg/l) Dec 20 192 20 13 125 No

As, TR (µg/l) * 1.6 0.015 1.6 58 0.56 Yes

Cd, Dis (µg/l) * 0.3 0.0029 0.30 0.9 0.0086 Yes

Cu, Dis (µg/l) * 4.3 0.041 4.3 47 0.45 Yes

CN, Free (µg/l) * ND 0 ND 31 0.3 Yes

Fe, TR (µg/l) * 70 0.67 70 3867 37 Yes

Pb, Dis (µg/l) * 1 0.0096 1.0 11 0.11 Yes

Mn, Dis (µg/l), AQ* 106 1 106 8925 86 Yes

Mo, TR (µg/l) * 10 0.096 10 1150 11 Yes

Hg, Tot (µg/l) * 0.04 0.00038 0.040 0.077 0.00074 Yes

Ni, Dis (µg/l) * ND 0 ND 219 2.1 Yes

Se, Dis (µg/l) * 0.4 0.0038 0.40 4.6 0.044 Yes

Ag, Dis (µg/l) * ND 0 ND 0.06 0.00058 Yes

Zn, Dis (µg/l) * 340 3.3 340 215 2.1 No

Nonylphenol (µg/l) * ND 0 ND 51 0.49 Yes

Note that loading for E. coli cannot be calculated; but, for comparison purposes, the approach is sufficient.

*NIL calculated from implicit limit, as described above

As shown in Table A-9b, there are no new or increased impacts to the receiving stream based on the new WQBELS for E. Coli, TRC, ammonia (January - April, November, December), or dissolved zinc, and for these parameters the AD evaluation is complete and the WQBELs are the final result of this WQA. For ammonia (May-October) and mercury, there are new or increased impacts and in accordance with regulation, the permittee has the option of choosing either the NILs or ADBACs. Because the ADBACs are generally more stringent than NILs, the Division assumes that the permittee will choose NILs rather than ADBAC’s, and therefore the Division will stop the AD evaluation at this point and assign the NILs to the permit. For those parameters where there is not a NIL (either implicit or explicit) the AD Guidance allows for the

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collection of data to determine an implicit limitation. Therefore, the permittee will be required to conduct “monitoring only” for those parameters. The permittee may request ADBAC limits. If the permittee does request ADBAC limits, the Division will proceed with the completion of this Antidegradation Analysis. For total arsenic, dissolved cadmium, dissolved copper, free cyanide, total iron, dissolved lead, dissolved manganese (aquatic life), total molybdenum, dissolved nickel, dissolved selenium, dissolved silver, and nonylphenol, there are new or increased impacts and in accordance with regulation, the permittee has the option of choosing either the NILs or ADBACs. Normally, the Division would assign the NILs as permit limitations, or prescribe monitoring to determine the appropriate implicit limitations as necessary, however, in this case, the NILs are very stringent and therefore the Division will automatically calculate the ADBACs for comparison. The final two significance determination tests (bioaccumulative and concentration) need to be applied, to determine if AD limits are applicable. For the bioaccumulative test, the determination of the baseline water quality (BWQ), the baseline water quality loading (BWQload), the threshold load (TL) and the threshold load concentration (TL conc) needs to occur. For the concentration test, the BWQ, significant concentration thresholds (SCT) and antidegradation based average concentrations (ADBACs) need to be calculated. These calculations are explained in the following sections, and each significance determination test will be performed as the necessary calculations are complete. The AD low flow may also need to be calculated when determining the BWQ for an existing discharger (as of Sept 2000) when upstream water quality data are used. Determination of Baseline Water Quality (BWQ) The BWQ is the ambient condition of the water quality as of September 30, 2000. The BWQ defines the baseline low flow pollutant concentration, and for bioaccumulative toxic pollutants, the baseline load. The BWQ is to take into account the influence of the discharger if the discharge was in place prior to January 28, 2014. In such a case, data from a downstream location should be used to determine the BWQ. If only upstream data is available, then a mass balance equation may be applied, using the facilities effluent data to determine the BWQ. If the discharge was not present prior to January 28, 2014, then the influence of that discharge would not be taken into account in determining the BWQ. If the BWQ has already been determined in a previous WQA AD evaluation, it may not need to be recalculated as the BWQ is the water quality as of January 28, 2014, and therefore should not change unless additional data is obtained or the calculations were in error. Consistent with current Division procedures, the BWQ concentrations for total arsenic, dissolved cadmium, dissolved copper, free cyanide, total iron, dissolved lead, dissolved manganese, total molybdenum, dissolved nickel, dissolved selenium, dissolved silver, dissolved zinc, and nonylphenol should be established so that it can be used as part of an antidegradation review. This discharger was in place as of January 28, 2014, and therefore the BWQ will include the influence of the discharger. Data collected at station AR-3B located on the Arkansas River directly downstream of the confluence with California Gulch, were determined to be representative of fully mixed condition downstream from the facility, without other influences, and thus the data were used to determine the BWQ concentrations. Since the data were collected downstream of the discharge, it takes into account the contribution of the facility. Currently, it is the Division’s approach to evaluate five years of ambient water quality data, if available, for the five years prior to January 28, 2014, when determining the BWQ. Data from this location were available for a period of record of May 2001 through September 2005. Although these data were not collected during the five years prior to January 2014, the Division has determined that, absent data available during the AD period, the available data are considered representative of ambient water quality during the AD review period. There were no data available for cyanide or nonylphenol, and therefore, the baseline water quality for these parameters was assumed to be zero.

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The ambient water quality data are summarized in Table A-10a. The BWQ concentrations based on these data, represented by the 50th percentile for total recoverable metals and total metals, the geometric mean for coliforms, and the 85th percentile for dissolved metals and other pollutants, are summarized in Table A-10b.

Table A-10a

Ambient Water Quality Data Summary for AD Period

Parameter Number of Samples

15th Percentile

50th Percentile

85th Percentile

Mean Location

As, TR (µg/l) 19 0 0 0.65 0.39 Downstream

Cd, Dis (µg/l) 34 0.23 0.52 1.5 0.97 Downstream

Cu, Dis (µg/l) 34 0 0 2.1 1.5 Downstream

Fe, TR (µg/l) 19 125 570 1294 757 Downstream

Pb, Dis (µg/l) 34 0 0.49 0.88 1.1 Downstream

Mn, Dis (µg/l) 24 20 88 476 209 Downstream

Mo, TR (µg/l) 24 0 0 0 3.9 Downstream

Ni, Dis (µg/l) 3 6 20 20 13 Downstream

Se, Dis (µg/l) 3 5.3 18 18 12 Downstream

Ag, Dis (µg/l) 20 0 0 0.3 0.54 Downstream

Table A-10b

BWQ Concentrations for Potential Pollutants of Concern Based on Downstream Ambient Water Quality Concentrations

Pollutant BWQ WQS

As, TR (µg/l) 0 7.6

Cd, Dis (µg/l) 1.5 0.9

Cu, Dis (µg/l) 2.1 8

CN, Free (µg/l) 0 5

Fe, TR (µg/l) 570 1000

Pb, Dis (µg/l) 0.88 2.2

Mn, Dis (µg/l), AQ 476 1578

Mo, TR (µg/l) 0 150

Ni, Dis (µg/l) 20 46

Se, Dis (µg/l) 18 4.6

Ag, Dis (µg/l) 0.3 0.06

Nonylphenol (µg/l) 0 6.6

In cases where the BWQ concentration exceeds the water quality standard, the calculated BWQ concentration must then be set equal to the water quality standard. This did not occur for any of the pollutants. Note that the AD requirements outlined in The Basic Standards and Methodologies for Surface Water specify that chronic numeric standards should be used in the antidegradation review; however, where there is only

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an acute standard, the acute standard should be used. Chronic standards were available for all pollutants except free cyanide. Bioaccumulative Significance Test For mercury, which is a bioaccumulative toxic pollutant, the bioaccumulative significance test would normally be completed, however, since the NIL will be the final chosen limit, this section is unnecessary. Significant Concentration Threshold The SCT is defined as the BWQ plus 15% of the baseline available increment (BAI), and is calculated by the following equation:

SCT = (0.15 × BAI) + BWQ The BAI is the concentration increment between the baseline water quality and the water quality standard, expressed by the term (WQS – BWQ). Substituting this into the SCT equation results in:

SCT = 0.15 × (WQS-BWQ) + BWQ Where, WQS = Chronic standard or, in the absence of a chronic standard, the acute standard BWQ = Value from Table A-10b When the BWQ concentration is equal to zero, the following equation results: SCT = 0.15 × WQS Determination of the Antidegradation Based Average Concentrations Antidegradation based average concentrations (ADBACs) are determined for all parameters except ammonia, by using the mass-balance equation, and substituting the SCT in place of the water quality standard, as shown in the following equation:

2

113

Q

QMQSCTADBAC

Where,

Q1 = Upstream low flow (1E3 or 30E3 based on either the chronic or acute standard) Q2 = Current design capacity of the facility Q3 = Downstream flow (Q1 + Q2) M1 = Current ambient water quality concentration (From Section III) SCT = Significant concentration threshold

The ADBACs were calculated using the SCTs, and are set forth in Table A-11.

Table A-11

SCTs and ADBACs

Pollutant Q1(cfs) Q2 (cfs) Q3 (cfs) M1 SCT ADBAC

As, TR (µg/l) 12 1.8 13.8 0 1.1 8.4

Cd, Dis (µg/l) 12 1.8 13.8 1.5 0.9 0.9

Cu, Dis (µg/l) 12 1.8 13.8 2.1 3 9

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CN, Free (µg/l) 9.5 1.8 11.3 0 0.75 4.7

Fe, TR (µg/l) 12 1.8 13.8 570 635 1068

Pb, Dis (µg/l) 12 1.8 13.8 0.88 1.1 2.6

Mn, Dis (µg/l) 12 1.8 13.8 476 641 1741

Mo, TR (µg/l) 12 1.8 13.8 0 23 176

Ni, Dis (µg/l) 12 1.8 13.8 20 24 51

Se, Dis (µg/l) 12 1.8 13.8 18 4.6 4.6

Ag, Dis (µg/l) 12 1.8 13.8 0.3 0.06 0.06

Nonylphenol (µg/l) 12 1.8 13.8 0 0.99 7.6

Concentration Significance Tests The concentration significance determination test considers the cumulative impact of the discharges over the baseline condition. In order to be insignificant, the new or increased discharge may not increase the actual instream concentration by more than 15% of the available increment over the baseline condition. The insignificant level is the ADBAC calculated in Table A-11 above. If the new WQBEL concentration (or potentially the TL Conc for bioaccumulatives) is greater than the ADBAC, an AD limit would be applied. This comparison is shown in Tables A-12.

Table A-12

Concentration Significance Test

Pollutant New WQBEL ADBAC Concentration Test Result

As, TR (µg/l) 58 8.4 Significant

Cd, Dis (µg/l) 0.9 0.9 Insignificant

Cu, Dis (µg/l) 47 9 Significant

CN, Free (µg/l) 31 4.7 Significant

Fe, TR (µg/l) 3867 1068 Significant

Pb, Dis (µg/l) 11 2.6 Significant

Mn, Dis (µg/l) 8925 1741 Significant

Mo, TR (µg/l) 1150 176 Significant

Ni, Dis (µg/l) 219 51 Significant

Se, Dis (µg/l) 4.6 4.6 Insignificant

Ag, Dis (µg/l) 0.06 0.06 Insignificant

Nonylphenol (µg/l) 51 7.6 Significant

For dissolved cadmium, dissolved selenium, and dissolved silver, the WQBELs are less than or equal to the ADBAC and therefore, the concentration test results in an insignificant determination. The WQBELs are the final result of this WQA for these parameters and AD limitations are not necessary. For all other parameters, the WQBELs are greater than the ADBACs and therefore, the concentration test results in a significance determination, and the antidegradation based effluent limitations (ADBELs) must be determined.

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Antidegradation Based Effluent Limitations (ADBELs) The ADBEL is defined as the potential limitation resulting from the AD evaluation, and may be either the ADBAC, the NIL, or may be based on the concentration associated with the threshold load concentration (for the bioaccumulative toxic pollutants). ADBACs, NILs and TLs have already been determined in the AD evaluation, and therefore to complete the evaluation, a final comparison of limitations needs to be completed. Note that ADBACs and NILs are not applicable when the new WQBEL concentration (and loading as evaluated in the New and Increased Impacts Test) is less than the NIL concentration (and loading), or when the new WQBEL is less than the ADBAC. Where an ADBAC or NIL applies, the permittee has the final choice between the two limitations. A NIL is applied as a 30-day average (and the acute WQBEL would also apply where applicable) while the ADBAC would be applied as a 2 year rolling average concentration. For the purposes of this WQA, the Division has made an attempt to determine whether the NIL or ADBAC will apply. The end results of this AD evaluation are in Table A-13, including any parameter that was previously exempted from further AD evaluation, with the final potential limitation identified (NIL, WQBEL or ADBAC).

Pollutant NIL New WQBEL ADBAC Chosen Limit

E. coli (#/100 ml) 1277 630* NA WQBEL

TRC (mg/l) 0.34 0.34 NA WQBEL

NH3 as N, Tot (mg/l) Jan 20 13 NA WQBEL

NH3 as N, Tot (mg/l) Feb 20 20 NA WQBEL

NH3 as N, Tot (mg/l) Mar 20 17 NA WQBEL

NH3 as N, Tot (mg/l) Apr 20 17 NA WQBEL

NH3 as N, Tot (mg/l) May 20 24 NA NIL

NH3 as N, Tot (mg/l) Jun 20 45 NA NIL

NH3 as N, Tot (mg/l) Jul 20 37 NA NIL

NH3 as N, Tot (mg/l) Aug 20 34 NA NIL

NH3 as N, Tot (mg/l) Sep 20 29 NA NIL

NH3 as N, Tot (mg/l) Oct 20 24 NA NIL

NH3 as N, Tot (mg/l) Nov 20 17 NA WQBEL

NH3 as N, Tot (mg/l) Dec 20 13 NA WQBEL

As, TR (µg/l) 1.6 58 8.4 ADBAC

As, Dis (µg/l) NA 2124 NA WQBEL

Cd, Dis (µg/l) 0.3 0.9 0.9 WQBEL

Cr+3, TR (µg/l) NA 767 NA WQBEL

Cr+3, Dis (µg/l) NA 514 NA WQBEL

Cr+6, Dis (µg/l) NA 84 NA WQBEL

Cu, Dis (µg/l) 4.3 47 9 ADBAC

CN, Free (µg/l) ND 31 4.7 ADBAC

Fe, TR (µg/l) 70 3867 1068 ADBAC

Pb, Dis (µg/l) 1.0 11 2.6 ADBAC

Table A-13

Final Selection of WQBELs, NILs, and ADBACs

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Mn, Dis (µg/l), AQ 106 8925 1741 ADBAC

Mo, TR (µg/l) 10 1150 176 ADBAC

Hg, Tot (µg/l) 0.04 0.077 NA NIL

Ni, Dis (µg/l) ND 219 51 ADBAC

Se, Dis (µg/l) 0.40 4.6 4.6 WQBEL

Ag, Dis (µg/l) ND 0.06 0.06 WQBEL

Zn, Dis (µg/l) 340 215 NA WQBEL

Sulfide as H2S (mg/l) NA 0.015 NA WQBEL

Nonylphenol (µg/l) ND 51 7.6 ADBAC

*The WQBEL for E. coli is calculated for COARUA06 (California Gulch), and is the most stringent WQBEL between the two receiving streams. For ammonia (May-October), and total mercury, the NIL has been established for this facility. The NILs were selected as they are less stringent than the WQBELs and the ADBACs. However, the facility has the final choice between the NILs and ADBACs, and if the ADBAC is preferred, the permit writer should be contacted. For the following parameters, total arsenic, dissolved copper, free cyanide, total iron, dissolved lead, dissolved manganese, total molybdenum, dissolved nickel, and nonylphenol, the ADBACs have been established for this facility. The ADBACs were selected as they are more stringent than the WQBELs and less stringent than the NILs, or perhaps due to the application as a two-year rolling average. However, the facility has the final choice between the NILs and ADBACs, and if the NIL is preferred, the permit writer should be contacted. For E. Coli, TRC, ammonia (January - April, November, and December), dissolved arsenic, total trivalent chromium, dissolved trivalent chromium, dissolved hexavalent chromium, dissolved cadmium, dissolved selenium, dissolved silver, dissolved zinc and sulfide, the WQBEL has been established for this facility. The WQBELs were selected as they are more stringent than the NILs or the ADBACs, or perhaps to give the facility time to collect data to establish implicit limits. Alternatives Analysis If the permittee does not want to accept an effluent limitation that results in no increased impact (NIL) or in insignificant degradation (ADBAC), the applicant may conduct an alternatives analysis (AA). The AA examines alternatives that may result in no degradation or less degradation, and are economically, environmentally, and technologically reasonable. If the proposed activity is determined to be important economic or social development, a determination shall be made whether the degradation that would result from such regulated activity is necessary to accommodate that development. The result of an AA may be an alternate limitation between the ADBEL and the WQBEL, and therefore the ADBEL would not being applied. This option can be further explored with the Division. See Regulation 31.8 (3)(d), and the Antidegradation Guidance for more information regarding an alternatives analysis. VIII. Technology Based Limitations Federal Effluent Limitation Guidelines The Federal Effluent Limitation Guidelines for domestic wastewater treatment facilities are the secondary treatment standards. These standards have been adopted into, and are applied out of, Regulation 62, the Regulations for Effluent Limitations. Regulations for Effluent Limitations Regulation No. 62, the Regulations for Effluent Limitations, includes effluent limitations that apply to all discharges of wastewater to State waters, with the exception of storm water and agricultural return flows.

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These regulations are applicable to the discharge from the proposed discharge. Table A-14 contains a summary of the applicable limitations for pollutants of concern at this facility.

Table A-14

Regulation 62 Based Limitations

Parameter 30-Day Average 7-Day Average Instantaneous

Maximum

BOD5 30 mg/l 45 mg/l NA

BOD5 Percent Removal 85% NA NA

TSS, mechanical plant 30 mg/l 45 mg/l NA

TSS Percent Removal 85% NA NA

Total Residual Chlorine NA NA 0.5 mg/l

pH NA NA 6.0-9.0 s.u.

Oil and Grease NA NA 10 mg/l

Nutrient Effluent Limitation Considerations WQCC Regulation No. 85, the new Nutrients Management Control Regulation, includes technology based effluent limitations for total inorganic nitrogen and total phosphorus that currently, or will in the future, apply to many domestic wastewater discharges to State surface waters. These effluent limits for dischargers are to start being implemented in permitting actions as of July 1, 2013, and are shown in the two tables below: Effluent Limitations Table at 85.5(1)(a)(iii) For all Domestic Wastewater Treatment Works not identified in subsections (a)(i) or (ii) above(in Reg. 85) and discharging prior to May 31, 2012 or for which a complete request for preliminary effluent limits has been submitted to the Division prior to May 31, 2012, the following numeric limits shall apply:

Parameter Parameter Limitations

Annual Median 1 95th Percentile 2

Total Phosphorus 1.0 mg/l 2.5 mg/l

Total Inorganic Nitrogen3 15 mg/l 20 mg/l

1 Running Annual Median: The median of all samples taken in the most recent 12 calendar months. 2 The 95th percentile of all samples taken in the most recent 12 calendar months. 3 Determined as the sum of nitrate as N, nitrite as N, and ammonia as N. Effluent Limitations Table at 85.5(1)(b) For New Domestic Wastewater Treatment Works which submit a complete request for preliminary effluent limits to the Division on or after May 31, 2012, the following numeric limits shall apply:

Parameter Parameter Limitations

Annual Median 1 95th Percentile 2

Total Phosphorus 0.7 mg/l 1.75 mg/l

Total Inorganic Nitrogen3 7 mg/l 14 mg/l

1 Running Annual Median: The median of all samples taken in the most recent 12 calendar months. 2 The 95th percentile of all samples taken in the most recent 12 calendar months. 3 Determined as the sum of nitrate as N, nitrite as N, and ammonia as N. Requirements in Reg. 85 also apply to non-domestic wastewater for industries in the Standard Industrial Class ‘Major Group 20,’ and any other non-domestic wastewater where the facility is expected, without treatment, to discharge total inorganic nitrogen or total phosphorus concentrations in excess of the numeric limits listed in 85.5 (1)(a)(iii). The facility must investigate, with the Division’s approval, whether different considerations should apply. All permit actions based on this WQA will occur after the July 1, 2013 permit implementation date of Reg. 85. Therefore, total inorganic nitrogen and total phosphorus effluent limitations potentially imposed because

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of Reg. 85 must be considered. However, also based on Reg. 85, there are direct exemptions from these limitations for smaller domestic facilities that discharge less than or equal to 1 million gallons per day (MGD), or are a domestic facility owned by a disadvantaged community. Delayed implementation (until 12/31/2027) is also specified in Reg. 85 to occur for domestic WWTFs that discharge more than 1 MGD, and less than or equal to 2.0 MGD, or have an existing watershed control regulations (such as WQCC Reg.’s 71-74), or where the discharge is to waters in a low-priority 8-digit HUC. For all other larger domestic WWTFs, the nutrient effluent limitations from the two tables above will apply, unless other considerations allowed by Reg. 85 at 85.5(3) are utilized to show compliance with exceptions or variances to these limitations. Because the design capacity of the Leadville Sanitation District WWTF is 1.15 MGD and the facility discharges to a low-priority 8-digit HUC (Arkansas Headwaters – 11020001), implementation of technology-based limits for total inorganic nitrogen and total phosphorus is delayed. The Division does not intend these results to discourage the Leadville Sanitation District WWTF from starting work on nutrient control with the other discharges in the area. This discharger and others upstream and downstream have the potential to create future nutrient issues in Arkansas River watershed. The Division encourages these entities to all work together to create the most efficient and cost effective solutions for nutrient control in the Arkansas River watershed. Supplemental Reg. 85 Nutrient Monitoring Reg. 85 also requires that some monitoring for nutrients in wastewater effluent and streams take place, independent of what nutrient effluent limits or monitoring requirements may be established in a discharge permit. The requirements for the type and frequency of this monitoring are set forth in Reg. 85 at 85.6. This nutrient monitoring is not currently required by a permitting action, but is still required to be done by the Reg. 85 nutrient control regulation. Nutrient monitoring for the Reg. 85 control regulation is currently required to be reported to the WQCD Environmental Data Unit. IX. References Regulations: The Basic Standards and Methodologies for Surface Water, Regulation 31, Colorado Department Public Health and Environment, Water Quality Control Commission, effective January 31, 2018. Classifications and Numeric Standards for Arkansas River Basin, Regulation No. 32, Colorado Department Public Health and Environment, Water Quality Control Commission, effective December 31, 2018. Regulations for Effluent Limitations, Regulation 62, CDPHE, WQCC, July 30, 2012. Nutrients Management Control Regulation, Regulation 85, Colorado Department Public Health and Environment, Water Quality Control Commission, effective September 30, 2012. Colorado’s Section 303(d) List of Impaired Waters and Monitoring and Evaluation List, Regulation 93, Colorado Department Public Health and Environment, Water Quality Control Commission, effective March 2, 2018. Policy and Guidance Documents: Antidegradation Significance Determination for New or Increased Water Quality Impacts, Procedural Guidance, Colorado Department Public Health and Environment, Water Quality Control Division, December 2001.

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Memorandum Re: First Update to (Antidegradation) Guidance Version 1.0, Colorado Department Public Health and Environment, Water Quality Control Division, April 23, 2002. Rationale for Classifications, Standards and Designations of Segments of the Arkansas River, Colorado Department Public Health and Environment, Water Quality Control Division, effective October 29, 2002. Policy Concerning Escherichia coli versus Fecal Coliform, CDPHE, WQCD, July 20, 2005. Colorado Mixing Zone Implementation Guidance, Colorado Department Public Health and Environment, Water Quality Control Division, effective April 2002. Policy for Conducting Assessments for Implementation of Temperature Standards in Discharge Permits, Colorado Department Public Health and Environment, Water Quality Control Division Policy Number WQP-23, effective July 3, 2008. Implementing Narrative Standards in Discharge Permits for the Protection of Irrigated Crops, Colorado Department Public Health and Environment, Water Quality Control Division Policy Number WQP-24, effective March 10, 2008. Policy for Characterizing Ambient Water Quality for Use in Determining Water Quality Standards Based Effluent Limits, Colorado Department Public Health and Environment, Water Quality Control Division Policy Number WQP-19, effective May 2002. Other: Bauder, T.A., R.M. Waskom, P.L. Sutherland and J. G. Davis. 2014. Irrigation Water Quality Criteria, Colorado State University Extension Fact Sheet no. 0.506. Undated October 03, 2014.

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Attachment 2

PROPOSED DETERMINATION

DATE: February 13, 2020

RE: Antidegradation Alternatives Analysis Review Leadville Sanitation District WWTF, Permit No: CO0021164

INTRODUCTION The Water Quality Control Division (division) received an alternatives analysis from the Leadville Sanitation District WWTF (permittee) on Monday August 19, 2019, in which the permittee requested the establishment of an alternative antidegradation-based effluent limitation (rather than the NIL included in the draft permit) for mercury (Hg). This alternatives analysis is included in the comments submitted during the public notice period for the draft Leadville SD WWTF permit (June 13, 2019 through August 19, 2019) and a supporting document drafted for the permittee by JVA, Inc., which includes appendices A-H. The division has compiled the alternatives analysis part of the comments into a separate document, which is available in the Alternatives Analysis document.

The draft permit (public notice on June 13, 2019) included total mercury limits of 0.077 µg/l (30-day average) as a water quality-based effluent limitation and 0.04 µg/l (30-day average) as an antidegradation-based effluent limitation after completion of the compliance schedule. The permittee has proposed an alternative limitation (ADBEL) of 0.31 µg/l (30-day average), which exceeds the WQBEL. The immediate receiving water is California Gulch (COARUA06).

The division is recommending denial of the permittee’s request to discharge 0.31 µg/l (30-day average) of mercury into California Gulch (COARUA06) as a requested alternative antidegradation based effluent limitation. This draft decision is subject to notice and comment as part of the re-noticed Leadville permit.

Draft Analysis of the AA, Including Draft Basis for Denial:

The Water Quality Control Commission has determined that certain high quality waters as “reviewable,” and are of high enough quality to deserve protection through the antidegradation rule. This rule “provides an extra layer of protection for the beneficial uses of the State's highest quality waters.” SBP, 31.43. To implement this direction, Permits includes antidegradation-based average concentrations and effluent limitations (ADBACs and ADBELs) as well as Non-Impact Limits (NILs) for reviewable waters pursuant to the division’s Antidegradation Significance Determination for New or Increased Water Quality Impacts Policy (“Antidegradation Policy”).

Regulation 31.8(d) allows a framework (called an Alternative Analysis (AA)) for the permittee to propose an alternative antidegradation-based limit that is higher than the limit calculated under the Antidegradation Policy. An AA is a way for the division to include in a permit a more lenient limit than the ADBAC or ADBEL but “in no case ... greater than a WQBEL.” Antidegradation Policy. In an AA, the division makes a determination that “lower water quality is necessary to accommodate important economic or social development in the area in which the waters are located.” § 25-8-209(5), C.R.S.; see also Reg. 31.8(3)(d) (referring to this as the “Necessity of Degradation Determination”). The division’s authority to approve AA limits is narrow and must meet the criteria in Regulation 31.8.

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The division denies the AA submitted by Leadville on the following grounds.

1. The permittee has proposed a numeric ADBEL (0.31 µg/l) that exceeds the WQBEL (0.077 µg/l). The division cannot accept an ADBEL larger than a WQBEL under the Antidegradation Policy and Regulation 31.8(3)(d). If “...a proposed regulated activity is likely to result in significant degradation of reviewable waters, a determination shall be made pursuant to this section whether the degradation is necessary to accommodate important economic or social development in the area in which the waters are located” (Regulation 31.8(3)(d). This provision addresses degradation and not exceedances of water quality standards. Under the Antidegradation Policy, “[i]n no case may an ADBEL be greater than a WQBEL.” (Antidegradation Policy, Section VI.F, emphasis added).

2. The permittee has not made the required showings for the necessity of degradation

Under Regulation 31.8(3)(d), the division can only approve alternative permit limits based upon the permittee’s AA if the division finds that: 1) the proposed regulated activity is important to economic or social development; and 2) the degradation that would result from such regulated activity is necessary to accommodate that development. To determine the latter, the degradation shall be considered necessary only if there are no water quality control alternatives available that: (A) would result in no degradation or less degradation of the state waters; and (B) are determined to be economically, environmentally, and technologically reasonable.

Regarding A, the Permits Section has determined that the regulated activity (municipal wastewater treatment) is important for economic or social development, based on information supplied by the permittee. In general, the Permits Section presumes that the activities are in fact important development unless information to the contrary is submitted during the public notice period.

Regarding B, the permittee must do the following, among other things, to show that the degradation is necessary:

Address all areas directly impacted by the proposed regulated activity as the “area in which the waters are located.” See Reg. 31.8(3)(d)(i) (“The ‘area in which the waters are located’ ... shall include all areas directly impacted by the proposed regulated activity”).

Show there are no water quality control alternatives available that: (A) would result in no degradation or less degradation of the state waters; and (B) are determined to be economically, environmentally, and technologically reasonable. Reg. 31.8(3)(d)(iii). This determination shall be based on an assessment of whether such alternatives are available and should address, among other things, practical water quality control technologies.

The permittee has not done these, as explained below.

Failure to Address All Areas Impacted

The permittee provided a description of areas that it alleges may be impacted by the discharge. However, this description excludes a number of areas directly impacted by the proposed regulated activity, as required. The permittee stated in Section 2 of the alternatives analysis report (p. 22 of 182 of the Alternatives Analysis PDF document) that infiltration and inflow into the collection system causes increased mercury. The same gaps in the collection system that allow infiltration and inflow (I/I) into the collection system may also allow untreated sewage to contaminate groundwater (exfiltration). The areas impacted by allowing ongoing I/I and potential untreated sewage into the groundwater were not addressed by the permittee.

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The permittee also failed to provide any evidence as to how the proposed mercury discharges will affect the receiving surface waters and the uses of those waters.

Failure to Consider Reasonable Alternatives

The permittee’s analysis did not include an alternative for source control of mercury. The information submitted by the permittee indicates that source control is a potential economically, environmentally, and technologically reasonable alternative and thus should have been considered in this AA. Specifically, the permittee’s collection system includes contributions from the Yak Tunnel WTP (showers, toilets, and sinks), which show high concentrations of mercury. In addition, the permittee stated in the alternatives analysis, that the Leadville Sanitation District collection system experiences inflow and infiltration, and surrounding soils from the California Gulch Superfund Site may contribute to high mercury in the influent. The permittee’s AA submission includes the following statement:

“The District’s sanitary sewer collection system is mostly comprised of vitrified clay pipe (VCP) that was installed before 1952, which is susceptible to joint separation and cracks. The District experiences inflow and infiltration (I/I) during spring runoff when groundwater levels rise. I/I from the CGSS was considered as a potential source of mercury contamination in the District’s collection system (Leadville Comments at p. 22 of 182 of the Alternatives Analysis PDF document).”

A source control alternative would have estimated the costs of repairing the collection system to reduce or eliminate infiltration and inflow. Instead of addressing maintenance and repairs to the collection system to reduce mercury entering the collection system, the facility focused on costs of treatment from continuing to allow this additional pollutant source.

Without consideration of a source control alternative, the division cannot determine whether the costs of the alternatives significantly exceed the costs of the draft permit’s ADBELs.

Use of Incorrect Cost Comparisons

As noted, the permittee has proposed AA limits that exceed the WQBELs. For an alternatives analysis, the comparison of costs must be performed against a proposed alternate limit that is less than or equal to the water quality based effluent limitation. The draft NIL is 0.04 µg/l and the draft WQBEL is 0.077 µg/l. The proposed ADBEL is 0.31 µg/l for mercury. The submitted alternatives analysis provides an economic comparison with the existing treatment facility:

“The costs of installing an additional low-level mercury removal technology significantly exceed the costs of continuing to remove total mercury to the concentrations achieved by existing treatment processes at the District’s WWTF (p.39 of 182 of the Alternatives Analysis PDF document).”

The existing treatment facility is currently discharging mercury at higher concentrations than the draft WQBEL. The permittee’s cost comparison uses the current operating costs that exceed the WQBEL as a comparison baseline. The facility has not performed an evaluation to compare the cost of meeting a qualifying alternative limit (less than or equal to the WQBEL) to the cost of meeting the draft NIL.

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