Rule Change Update MPCA 1/13/05. 7081 Mid-Sized ISTS (MSTS)

Rule Change UpdateRule Change UpdateMPCAMPCA1/13/051/13/05

7081 Mid-Sized ISTS 7081 Mid-Sized ISTS (MSTS)(MSTS)

I. ScopeI. Scope

A. Standards to reasonably A. Standards to reasonably protect surface water, ground protect surface water, ground water, and public health, safety, water, and public health, safety, and general welfare.and general welfare.

I. ScopeI. Scope

B. Mainly performance outcomes B. Mainly performance outcomes provided with some prescriptive provided with some prescriptive design, construction, and design, construction, and operational standards.operational standards.

I. ScopeI. Scope

C. Systems designed under this C. Systems designed under this part may require additional part may require additional design requirements pursuant to design requirements pursuant to EPA Class V regulations.EPA Class V regulations.

I. ScopeI. Scope

• Chapter 7081 - mid-sized ISTS Chapter 7081 - mid-sized ISTS (MSTS) (MSTS)

– Multiple dwellings or Other Multiple dwellings or Other Establishments - 2,500 to 10,000 Establishments - 2,500 to 10,000 gpd gpd

I. ScopeI. Scope

Sewage collection system Sewage collection system – Piping, lift stations or components Piping, lift stations or components

that conveys sewage that conveys sewage – On-lot sewage tank = MSTSOn-lot sewage tank = MSTS

I. ScopeI. Scope

H. Administration of chapter 7081 H. Administration of chapter 7081 standards is done by local standards is done by local permitting authorities. permitting authorities.

SDS Permit ThresholdSDS Permit Threshold

• One or more systemsOne or more systems

• Average daily flow of greater Average daily flow of greater than 10,000 gallons per day than 10,000 gallons per day

• ½ mile radius½ mile radius

• Single ownershipSingle ownership

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SDS Permit ThresholdSDS Permit Threshold

• Any system the commissioner Any system the commissioner has determined needs a SDS has determined needs a SDS permit.permit.

• Flow amounts to determine if an Flow amounts to determine if an SDS permit is required must be SDS permit is required must be per 7081.0110per 7081.0110

Performance and Performance and Compliance CriteriaCompliance Criteria

– No contact with sewage. No contact with sewage. – Safe systems - protection Safe systems - protection

from from physical injury and physical injury and harm.harm.

– Accepted no hazardous Accepted no hazardous material.material.


Groundwater protectionGroundwater protection

– No fecal organism in groundwaterNo fecal organism in groundwater

– Systems that comply with any Systems that comply with any nitrogen or phosphorus standardnitrogen or phosphorus standard


Other conformanceOther conformance

– In conformance with the In conformance with the operating permit.operating permit.

IV. Professional IV. Professional Requirements. Requirements.

A. MSTS DesignerA. MSTS Designer

B. InstallerB. Installer

C. MSTS InspectorC. MSTS Inspector

D. MaintainerD. Maintainer

E. Service ProviderE. Service Provider

Sewage Flow Sewage Flow Determination Determination

DwellingsDwellings

– Use Type II flows for 10+ dwellingsUse Type II flows for 10+ dwellings

V. Sewage Flow V. Sewage Flow DeterminationDetermination

OtherOther

– Include 200 gallons of infiltration Include 200 gallons of infiltration and inflow per inch of collection and inflow per inch of collection pipe diameter per mile per day. pipe diameter per mile per day.

VI. Soil And Site VI. Soil And Site EvaluationEvaluation

Normal preliminary evaluation Normal preliminary evaluation plus:plus:

– Distance to surface waterDistance to surface water

– Waste strength Waste strength

Soil And Site EvaluationSoil And Site Evaluation

Soil pits required - one pit per Soil pits required - one pit per corner and one the center, plus corner and one the center, plus one additional soil pit per 10,000 one additional soil pit per 10,000 ft2.ft2.

Soil And Site EvaluationSoil And Site Evaluation

Must determine perc rate by both Must determine perc rate by both water testing and texture, water testing and texture, structure and consistence. structure and consistence.

Groundwater Groundwater InvestigationInvestigation

A preliminary groundwater A preliminary groundwater evaluation for all MSTSevaluation for all MSTS

Groundwater InvestigationGroundwater Investigation

A determination of :A determination of :

• shallow groundwater settingshallow groundwater setting

• regional groundwater settingregional groundwater setting

• aquifer(s) used for water aquifer(s) used for water supplysupply

• wellswells

• groundwater flow directiongroundwater flow direction


A determination if contaminant A determination if contaminant plumes may intersect water plumes may intersect water supply wells capture zonessupply wells capture zones


• An estimation of the extent of An estimation of the extent of groundwater mounding from the groundwater mounding from the operating system. operating system.

• The accuracy of the The accuracy of the approximation shall be approximation shall be determineddetermined

Groundwater InvestigationGroundwater Investigation

The designer must consult with The designer must consult with the permitting authority for the the permitting authority for the extent of any further extent of any further investigation or monitoringinvestigation or monitoring

Design Standards.Design Standards.

A flow measure device must be A flow measure device must be employed on all MSTS.employed on all MSTS.

Design Standards.Design Standards.

The system must be designed with The system must be designed with sufficient access and ports to sufficient access and ports to monitor the system as monitor the system as applicable. applicable.

IX. Sewage Tanks.IX. Sewage Tanks.

• Septic tank size = average daily Septic tank size = average daily flow by 3.0. flow by 3.0.

• Septic tank size under pressure Septic tank size under pressure = the average daily flow by = the average daily flow by 4.0. 4.0.

Sewage Tanks.Sewage Tanks.

Septic tank capacity prior to other Septic tank capacity prior to other treatment devices, shall be per treatment devices, shall be per manufacturer’s requirements or manufacturer’s requirements or accepted engineering principals.accepted engineering principals.


Tanks shall be connected in Tanks shall be connected in series. Parallel OK if sufficient series. Parallel OK if sufficient justification is provided and justification is provided and adequate monitoring is provided. adequate monitoring is provided.


All tanks used for MSTS shall be All tanks used for MSTS shall be tested for water tightness. tested for water tightness.

Food preparation facility, shall Food preparation facility, shall install an external grease trap. install an external grease trap.

Distribution Of Effluent. Distribution Of Effluent.

Distribution in accordance with Distribution in accordance with 7080.01607080.0160

Designed for a 2 foot head.Designed for a 2 foot head.

DOSING OF EFFLUENT. DOSING OF EFFLUENT.

Dosing in accordance with Dosing in accordance with 7080.01607080.0160

Final Treatment and Final Treatment and Disposal.Disposal.

Systems setback from site Systems setback from site boundaries, downgradient of boundaries, downgradient of groundwater flow 50’ + groundwater flow 50’ + ((average design flow – 1500) ((average design flow – 1500) x .03’)x .03’)


Sized with a 50% increased plus Sized with a 50% increased plus 50% reserve. 50% reserve. (not for less than 2,500 (not for less than 2,500

gpd).gpd).


SizingSizingHydraulicHydraulic

flowflowsoilsoilgw moundinggw mounding

NitrogenNitrogenPhosphorusPhosphorusOrganics (biomat)Organics (biomat)Pathogen removalPathogen removal


Table I I I Waste Strength Loading Rates Soil Texture lbs. of BOD/ 100

f t2/ day of bottom absorption area*

lbs. of TSS / 100 f t2/ day of bottom absorption area*

lbs. of O&G/ 100 f t2/ day of bottom absorption area*

Sand 0.11 0.033 0.015 Sandy loam 0.07 0.021 0.010 loam and fi ne sand 0.06 0.016 0.007 Silt loam 0.05 0.014 0.006 Clay loam 0.02 0.012 0.003


Separation Distance depends on:Separation Distance depends on:– Soil texture Soil texture – Loading rateLoading rate– Dosing frequencyDosing frequency– System width and depthSystem width and depth– Capillary fringe Capillary fringe – Groundwater mounding Groundwater mounding – Concentrations of contaminantsConcentrations of contaminants– Hydraulic head Hydraulic head – Factor of safetyFactor of safety


• An unsaturated zone must be An unsaturated zone must be maintained.maintained.

• Measure the height of the Measure the height of the seasonally saturated soil during seasonally saturated soil during operation. operation.

• Systems might need to employ Systems might need to employ nitrogen and phosphorus nitrogen and phosphorus reduction methods. reduction methods.

XConstruction XConstruction

Designer must observe critical Designer must observe critical periods of system construction periods of system construction

Operation and Operation and Maintenance.Maintenance.

Operated under a local operating Operated under a local operating permitpermit

System Ownership and System Ownership and ResponsibilityResponsibility

– Apply for and obtain construction and Apply for and obtain construction and operating permits;operating permits;

– Ensure submittal of required Ensure submittal of required reporting and compliance status to the reporting and compliance status to the permitting authority;permitting authority;

– Negotiate contracts as necessary;Negotiate contracts as necessary;

- recover costs of damages to the - recover costs of damages to the system;system;

- able to obtain financing- able to obtain financing

System Ownership and System Ownership and ResponsibilityResponsibility

– Provide annual education to users Provide annual education to users on suitable discharges;on suitable discharges;

– Monitor compliance with local Monitor compliance with local ordinances requirements ordinances requirements

- financial instrument to continue the - financial instrument to continue the operation, maintenance, operation, maintenance, management, repairs, of the system management, repairs, of the system for a period of one year for a period of one year

Rule Change Update MPCA 1/13/05. 7081 Mid-Sized ISTS (MSTS)

Documents

gpd slide

groundwater systems

groundwater investigation

service provider slide

phosphorus standard

regional groundwater

shallow groundwater

midsized ists msts slide