STORMWATER MANAGEMENT IN RHODE ISLANDs3.amazonaws.com/ebcne-web-content/fileadmin/pres/10-13...•Low Impact Development (LID) Site Planning and Stormwater Design. •Re-development

STORMWATER MANAGEMENT IN RHODE ISLAND

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STAKEHOLDER’S PERSPECTIVE & EXPERIENCE WITH THE RISDI MANUAL

Presented by Len Bradley Jr. P.E.

Vice President DiPrete Engineering October 2013

MAJOR CHANGES TO RI STORMWATER

•2010 Design & Installation Manual (RISDIM)

•Low Impact Development (LID) Site Planning and Stormwater Design.

•Re-development projects now require new stormwater water quality mitigation.

•Eleven (11) minimum standards to be met on all development projects.

•Structural practices divided into “Water Quality Practices” and “Storage Practices”.

•Design rainfall: Increased substantially to 8.9 in - 9.3 in for the 100-year storm event

•New RIPDES CGP as of 9/26/2013

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PRIOR TO 2010 RISDIM STORMWATER DESIGN NEEDED TO COMPLY WITH THE SEPTEMBER 1, 1993 RISDIM

Most drainage design consisted of interconnected catch basins which collected stormwater run-off and directed it to a stormwater basin which could have been above ground or below ground and would either detain to mitigate peak run off or retain entire storm event.

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WITH THE ADOPTION OF THE 2010 RI STORMWATER DESIGN AND INSTALLATION MANUAL: Managing storm water run-off takes much more of an effort by the engineer to design.

The 2010 RISDIM requires much more treatment and filtration of the stormwater than the 1993 RISDIM.

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We are now required to integrate pre-treatment and water quality treatment into the proposed stormwater management systems. Pretreatment practices we are using include sedimentation fore-bays and fitter strips prior to WQ treatment. This is the first opportunity to remove sediments from storm water

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Our typical stormwater management systems still include catch basins and drainage networks to collect and convey stormwater, but not always.

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Chapter 3: Stormwater

Management Standards and

Performance Criteria 12 Minimum Standards:

3.2.1 LID site planning and design strategies must be

used to the maximum extent practicable.

• Stormwater Management Plan checklist

(Appendix A)

3.2.2 Stormwater must be recharged to maintain base

flow at pre-development recharge rates to the

maximum extent practicable.

• Groundwater dewatering at a site is not allowed.

• Recharge volume equation – based on

Hydrologic Soil Group (HSG).

• Case-by-case waiver possible: i.e. if GWT < 3’

throughout the site.

• Design practice: bottom of infiltration practice

must be located below existing grade (not in fill).

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3.2.3 Stormwater management controls must be

designed to achieve the following minimum

pollutant removal requirements at each

discharge location based on the water quality

volume: 90% TSS, 90% bacteria removal, and

either 40% removal of total phosphorus for

freshwater discharges or 30% total nitrogen for

saltwater discharges.

• Structural practices listed in Chapter 5 can be

assumed to meet these standards if designed,

constructed and maintained to treat 100% of

the water quality volume.

3.2.4 Open drainage and pipe conveyance systems

must be designed to provide adequate passage

of flows leading to, from, and through

stormwater management facilities for at least

the 10-year, 24-hour design storm event.

Protection for natural channels downstream

must be supplied by providing 24-hour

extended detention of the one-year, 24-hour

design storm event.

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3.2.5 Downstream overbank flood protection must be

provided by attenuating the post-development peak

discharge rate to the pre-development levels for the

10-year and 100-year, 24 hour storm events. Also

demonstrate that runoff from the site for storms up

to the 100-year, 24-hour design storm events

actually reach proposed structural practices.

3.2.6 The construction of new impervious areas on

undeveloped land is subject to the Manual

requirements even if other portions of the site are

currently developed.

• Redevelopment: any construction, alteration, or

improvement that disturbs a total of > 10,000 sq.

ft. of existing impervious area.

• < 40% existing impervious surface: stormwater

management requirements are same as for new

development.

• > 40% impervious coverage: either 50% reduction

in existing impervious area, water quality treatment

of 50% impervious, or combination.

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3.2.7 Stormwater pollution prevention plan

(SWPPP)

• Representative techniques in Appendix G.

3.2.8 Stormwater discharges from land uses with

higher potential pollutant loads (“LUHPPLs”)

require the use of specific source control and

pollution prevention measures and the

specific stormwater BMPs approved for such

use.

• LUHPPLs = industrial sites, auto fueling

facilities, exterior vehicle maintenance

areas, road salt storage areas, etc.

• Most structural practices may still be used,

but must be lined to prevent infiltration into

existing soil.

3.2.9 All illicit discharges to stormwater

management systems are prohibited,

including discharge from OWTS, and sub-

drains and French drains near OWTSs that

do not meet the State’s OWTS Rules.

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3.2.10 Erosion and sedimentation control (ESC)

practices must be utilized during the

construction phase as well as during any land

disturbing activities.

• Temporary sediment trapping practices must be

sized for 1 inch of runoff.

• Temporary conveyance practices must be sized

to handle flow from the 10-year, 24-hour design

storm.

• Follow the “Rhode Island Soil Erosion and

Sediment Control Handbook”.

3.2.11 The stormwater management system must

have an operation and maintenance plan to

ensure it continues to function as designed.

• Includes owner name(s), responsible parties,

routine/non-routine maintenance tasks, plan

drawn to scale w/all stormwater BMPs in each

treatment train along w/discharge point, ID

public safety features, estimated operation &

maintenance budget, and funding source.

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4.3 LID GOALS

The purpose of LID is to reduce the environmental impact “footprint” of a development site while retaining and enhancing the owner/developer’s purpose and vision for the site. Many of the LID concepts employ non-structural, on-site treatment that can reduce the cost of infrastructure while maintaining or even increasing the value of the property relative to conventionally designed developments.

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• Reduce impervious cover and thus the

generation of stormwater runoff volume;

• Prevent impacts to natural drainage ways,

surface waters, and wetlands;

• Manage water (quantity and quality) as close to

the source as possible and minimize the use of

large stormwater collection and conveyance

systems;

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• Preserve natural areas, native vegetation, and

reduce the impact on watershed hydrology;

• Protect natural drainage pathways as a

framework for site design;

• Utilize less complex, non-structural methods for

stormwater management that are lower cost and

lower maintenance than conventional structural

controls; and

• Create a multifunctional landscape.

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These Minimum Standards can be at odds with the Goals and Objectives of the Land Owner, Developer and Municipality’s Zoning By-laws/ Comprehensive Plan

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Chapter 5: Structural Stormwater

Treatment Practices for Meeting Water

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Chapter 6: Pretreatment Practices

1) Grass Channels

2) Filter Strips

3) Sediment Fore-bays

4) Deep Sump Catch Basins

5) Proprietary Devices

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Chapter 7: Storage Practices for

Stormwater Quantity Control

1) Stormwater Basins (Wet & Dry

Extended Detention)

2) Underground Storage Devices

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• These new stormwater systems take more of an effort to get approved by the Towns and Cities.

• Most Towns’ Land Development regulations have not caught up with the 2010 RISDIM design criteria.

• Most subdivision regulations still require wide paved roadways, catch basins, sidewalks and curbing.

• This typical roadway cross section is not conducive to LID which requires less pavement and or sidewalks and minimal to no curbing.

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• Long turn maintenance of these new stormwater systems is a concern for many Towns that are not equipped to maintain the systems due to funding or personnel issues

• RIDEM is now requiring that an Operation and Maintenance Manual (O& M) and Storm Water Pollution Prevention Plan (SWPPP) be prepared for each project they review and approve.

• Prior to 2010 the O&M and SWPPP where included in our Stormwater Management and Soil Erosion / Sediment Control Report.

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As a Professional Engineer our job is to achieve the

goals and objectives of our Client’s while working

with the Regulators to meet the requirements of the

Town & State’s regulations.

What ultimately happens is real estate development

and re-development projects designed using the

2010 RISDI Manual end up experiencing increased

development and construction cost as a result of the

new RISDI Manual.

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Our experience, unfortunately, is that this has led to

the dis-investment in some economically important

projects and that owners have chosen to not

redevelop or invests in properties because of the high

construction cost and loss of usable parking.

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Rhode Island Pollution Discharge Elimination System’s (RIPDES) as of September 26, 2013 In addition to the 2010 RISDI Manual Land Owner and Developers not also need to comply with the new 2013 Rhode Island Pollution Discharge Elimination System’s (RIPDES) requirements. http://www.dem.ri.gov/pubs/regs/regs/water/ripdesca.pdf

Land owners / Permit holders are receiving notice from RIDEM which give them notice that the 2008 RIPDES CGP has been replaced by the 2013 RIPDES CGP.

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The Office of Water Resources, Rhode Island Pollutant Discharge Elimination System's (RIPDES) files indicate that your facility has been authorized to discharge stormwater associated with construction- activity under the RIPDES General Permit which became effective on September 26, 2008, and expired on September 25, 2013. Please be advised that a minor permit modification was made to the permit. For stormwater discharges associated with construction activities which were authorized under the 2008 Construction Activity General Permit which are expected to continue beyond the effective date of this permit and the owner is required to reapply, an NOI is required to be submitted within sixty (60) days of the effective date of the final permit in order to maintain permit coverage in accordance with Part 1.0.3 of the permit.

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Due to the fact that your original authorization to discharge was granted by the RIPDES Permitting Program you are required to submit a revised NOI to the DEM RIPDES Permitting Program by November 26, 2013 in order to be automatically authorized to discharge under the 2013 RIPDES CGP. In addition, all previously authorized projects that wish to maintain authorization to discharge under the 2013 CGP must also modify their existing Stormwater Management Plan to comply with Part II .B of the permit by November 26, 2013. The Notice of Intent includes a certification statement which must be signed which serves as acknowledgement that the Soil Erosion, Runoff, and Sediment Control elements of the Stormwater Management Plan have been reviewed and updated to comply with the 2013 RIPDES CGP. Revisions to the Stormwater Management Plan must be maintained on site and do not need to be resubmitted to the OEM.

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Please also note that a permit application fee is not required for previously authorized projects seeking reauthorization, however the annual fee will apply until a Notice of Termination is submitted to the OEM. Revisions to the Stormwater Management Plan must be maintained on site and do not need to be resubmitted to the OEM. Please also note that a permit application fee is not required for previously authorized projects seeking reauthorization, however the annual fee will apply until a Notice of Termination is submitted to the OEM.

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DE has reviewed the changes to the new RIPDES SWPPP requirements. • There are some minor changes to the actually SWPPP

template published by RIDEM, • RIDEM is calling for more detailed soil erosion control

plans during construction including the design and installation of sedimentation basins.

• RIDEM may require that large scale projects design and detail construction phase sedimentation & soil erosion control measures. o It seems that any project that will be channelizing

stormwater during construction will be required to comply with this part of the RIPDES SWPPP.

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How does this affect RI’S current projects and tolled projects? • Required to update project SWPPP to comply with the

new regulations. • Per the new regulations any previously approved project

will require a new SWPPP and possibly a new NOI. If a project was submitted only to RIDPES for an NOI, a new NOI is required. • Resubmission would need to include an updated SWPPP

and potentially soil erosion control plans depending on the project.

• Project owners will receive a notification about this.

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Projects that have RIDPES permit but were submitted as part of another permit (UIC, WQ, Wetlands, CRMC (this includes wetland permits approved by OCTA)), don’t need to resubmit but should have an updated SWPPP / Soil Erosion Controls onsite.

• Some projects are probably in better shape than others, newer project likely have used the RIDEM SWPPP template so they are close to complying with new RIPDES.

• Older projects likely are not using the current RIDEM SWPPP and therefore would need major SWPPP update’s.