Low Impact Development Training

Module 1: Background

Part 3: D.C. Stormwater Regulations

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Sponsors

District Department of Transportation

U.S. Department of Transportation Federal Highway Administration

The Low Impact Development Center, Inc.

University of the District of Columbia

Funding for this project was provided through a grant from the Federal Highway Administration, U.S. Department of Transportation

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Contributors

The Low Impact Development Center, Inc.

John Shorb Landscaping, Inc.Logo

Groundwork Anacostia River, D.C.

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Copyright

Unless otherwise noted, Low Impact Development Training, funded by DDOT & DDOE, is licensed under a Creative Commons Attribution-NonCommerical-ShareAlike 3.0 Unported License.

Content provided by cited entities remains the property of those entities and may not be used without their explicit permission.

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Overview

• Development projects in the District are required to take steps to limit the amount of stormwater runoff discharged to city storm sewers and receiving waters.

• This module will provide an overview of DDOE stormwater regulations

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Expected Outcomes

• Know what stormwater requirements are triggered by construction

• Be able to navigate the process of preparing and submitting a stormwater management plan for a construction project

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Outline

• Design requirements• Permitting process• Construction and maintenance inspections• Fines and corrective actions

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Supplemental Information

• Note that slides with orange backgrounds contain supplemental details that are provided for informational purposes, but which are not required content for this course

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Principal Players

• Owner• DDOE – District Department of the

Environment– Responsible for stormwater regulation– Set rules, issue permits, conduct inspections

• DDOT – District Department of Transportation– Own many bioretention installations in the

right-of-way

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Green Area Ratio

• Proposed change to District zoning codes• Sets standards for landscape design • Required Green Area Ratio (GAR) score

varies by zone• Encourages green space and promotes

infiltration

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D.C. Stormwater Regulations

• Stormwater is regulated by the District Department of the Environment (DDOE)

• A revised Stormwater Guidebook was adopted in July 2013

• Increased focus on retention for stormwater quality and quantity control

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DDOE Stormwater Requirements

• Retention requirements• Detention requirements• Extreme flood requirements• Water quality requirements

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What activities trigger these requirements?

• Major Land Disturbing Activities:– Soil disturbance is greater than 5,000 square

feet

• Major Substantial Improvement Projects:– Combined footprint of building improvements and

land disturbance is greater than 5,000 square feet

• All land disturbing activities requiring a building permit also require an erosion and sediment control plan, regardless of size

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Retention requirements

• Require that a certain volume of stormwater runoff be captured and not discharged

• Retention requirements target small, every day rainstorms, which are responsible for most stormwater pollution

• Required retention volume is calculated using a Compliance Spreadsheet

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Retention requirements

Photo Courtesy of Emily Ayers

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Retention requirements

• For Major Land Disturbing Activities:• Retain a volume equal to post-development

rainfall from 90th percentile event (1.2 inches)

• For Major Substantial Improvement Activities:• Retain a volume equal to post-development

rainfall from 80th percentile event (0.8 inches)

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Retention requirements

• Retention requirements apply to each drainage area on site

• Excess retention in one area may be credited toward other areas up to the 1.7 inch storm

Graphic Courtesy of the Low Impact Development Center, Inc.

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Off-site retention

• Off-site retention may be used for up to 50% of retention requirement

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Projects in the Right-of-Way

• Must meet retention requirements only to the Maximum Extent Practicable

• Details in Guidebook Appendix B

Photo Courtesy of DDOT

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Stormwater Retention Credits

• If a project achieves retention in excess of what is required, the excess can be awarded Stormwater Retention Credits (SRCs)

• SRCs can then be sold for use as offsite retention for other projects

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Detention Requirements

• Apply to larger, infrequent storm events• Require that a certain quantity of

stormwater runoff be held back temporarily, so that stormwater flow rates do not reach damaging levels

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Flood control requirements

• Apply to very large, very infrequent storms (once in 100 years)

• Triggered when proposed development is likely to increase flooding

• This can happen when development involves filling in a floodplain, or dramatically increasing imperviousness of a watershed

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Water quality requirements

• Treated effluent concentration of oil and grease must be less than 10 mg/L

• 60% of Total Suspended Solids (TSS) must be removed

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Accepted BMPs

• Green roofs• Rainwater harvesting• Impervious surface disconnection• Permeable pavement systems• Bioretention• Filtering systems• Infiltration• Open channel systems• Ponds• Wetlands• Storage practices• Proprietary practices• Tree planting and preservation

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Green roofs

Two types:

• Extensive (3-6” media)

• Intensive (6”-4’ media)

R Retention

Detention

R Water Quality

ASLA Headquarters Green Roof, Washington DCPhoto Courtesy of the Low Impact Development Center, Inc.

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Rainwater harvesting

• Rain barrels or cisterns

• Captured rainfall can be used for irrigation and non-potable applications

• Consult District Construction Codes (DCMR, Title 12) for allowable indoor uses

R Retention

Detention

R Water Quality

Photo Courtesy of Robb Lukes

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Impervious surface disconnection

• Disconnect downspouts or impervious surfaces to drain toward pervious areas

R Retention

Detention

R Water Quality

Infiltration Planter, Navy Yard, Washington DCPhoto Courtesy of the Low Impact Development Center, Inc.

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Permeable pavement systems

• Porous asphalt• Pervious concrete• Permeable interlocking

concrete pavers / concrete grid pavers

• Plastic grid pavers

R Retention

Detention

R Water Quality

Navy Yard, Washington DCPhoto Courtesy of the Low Impact Development Center, Inc.

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Bioretention

Several different variations:• Traditional

bioretention• Streetscape

bioretention• Engineered tree pits• Stormwater planters• Residential rain

gardens

R Retention

Detention

R Water Quality

Edmonston, MDPhoto Courtesy of the Low Impact Development Center, Inc.

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Filtering systems

• Use sand or other media to filter stormwater

Retention

Detention

R Water Quality

Photo Courtesy of DDOE

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Infiltration

• Infiltration trench• Infiltration basin• Must be located in

areas with high infiltration rates

• Must be set back from foundations and pavement

R Retention

Detention

R Water Quality

Photo Courtesy of the Low Impact Development Center, Inc.

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Open channel systems

• Grass channels• Dry swales• Wet swales• Used to convey runoff

from drainage area to other BMPs

• Provide limited water quality and retention benefits

R (Dry swales) Retention

Detention

R Water Quality

Photo Courtesy of the Low Impact Development Center, Inc.

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Ponds

• Used to provide detention for large events

• Included if necessary at end of treatment train

Retention

R Detention

R Water Quality

Photo Courtesy of the Low Impact Development Center, Inc.

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Wetlands

• Used to provide detention for large events

• Included if necessary at end of treatment train

• Drainage area must be large enough to sustain a permanent water level

Retention

R Detention

R Water Quality

Photo Courtesy of Emily Ayers

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Storage practices

• Underground vault• Dry pond• Rooftop storage• Stone storage under

permeable pavement or other BMPs

• Used for detention of stormwater from large events

Retention

R Detention

Water Quality

Photo Courtesy of the Low Impact Development Center, Inc.

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Proprietary practices

• Must be approved by DDOE

• Provide water quality treatment

Retention

Detention

R Water Quality

Photo Courtesy of Larry Coffman.

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Tree planting and preservation

• Preserve existing trees

• Plant and maintain new trees

• Reduce runoff volume• Improve infiltration• Use tree canopy to

intercept rainfall over paved areas

R Retention

Detention

R Water Quality

Photo Courtesy of the Low Impact Development Center, Inc.

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BMP Selection

• BMPs are selected based on a 5-step screening process:1. Stormwater management suitability

2. Land use factors

3. Physical feasibility factors

4. Community and environmental factors

5. Location and permitting considerations

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1. Stormwater management suitability

• Select BMPs or combinations of BMPs that will meet retention, detention, and water quality requirements

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2. Land use factors

• Select BMPs most suitable for the land use:– Residential– Commercial

development– Roads and highways– Hotspot land uses

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3. Physical feasibility factors

• Select BMPs that are feasible given the physical conditions onsite:– Underlying soils– Water table depth– Contributing drainage

area– Practice surface slope– Head

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4. Community and environmental factors

• Consider community and environmental factors:– Maintenance burden– Cost– Safety risk– Space required– Environmental factors– Habitat value

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5. Location and permitting considerations

• Prohibitions• Regulated areas• Setbacks

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Permitting Process

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Permitting Process (cont’d)

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1. Submit application package

• Submitted to DCRA Permit Service Center• Includes:

– Stormwater Management Plan (SWMP)• Requests for:

– Public Right-of-Way MEP– Exemption for extraordinarily difficult site conditions– Use of proprietary practice

– Soil Erosion and Sediment Control Plan (SESCP)

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SWMP

• A Stormwater Management Plan (SWMP) contains: – supporting computations– drawings– sufficient information to evaluate the environmental

characteristics of the affected areas– the potential impacts of the proposed development on water

resources – the effectiveness and acceptability of Stormwater Best

Management Practices (BMPs) for managing stormwater runoff

– maintenance and construction schedules– number of gallons the applicant shall retain off-site (where

applicable)

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Site Plan

Graphic Courtesy of the Low Impact Development Center, Inc.

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Stormwater Hotspots

• H-1 Vehicle Maintenance and Repair• H-2 Vehicle Fueling• H-3 Vehicle Washing• H-4 Vehicle Storage• H-5 Loading and Unloading• H-6 Outdoor or Bulk Material Storage• If any of the above operations are expected to occur on a

planned development site, the• Stormwater Hotspot Cover Sheet should be completed.

Further, a stormwater pollution• prevention plan (SWPPP) or the Stormwater Hotspot

Checklist

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Required supporting documents

(1) Site Development Submittal Information Form

(2) DC Water Storm Sewer Verification Form

(3) DCRA Application for Construction Permit on Private Property

(4) Environmental Intake Screening Form (EISF)

(5) Environmental Questionnaire

(6) DC Green Building Act Permit Application Intact Form

(7) Contract Agreement

(8) Lead Permit Screening Form

(9) Zoning Data Summary Form

(10) Reasonable Accommodations and Modifications for Persons with Disabilities Form

 

Forms 1 and 2 are found in Section 5.7 of the Guidebook. Forms 3 through 10 are available at the DCRA intake counter or can be downloaded at: http://dcra.dc.gov/DC/DCRA/Permits/Building+Permit+Application+Supplemental+Documents

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Current fees (as of 2013)SWMP Review Land disturbance

≥5,000sf & ≤10,000sf

Land disturbance ≥10,000sf

Initial plan review due upon filing $3,300.00 $6,100.00

Final plan review due before issuance of building permit

$1,500.00 $2,400.00

Supplemental review fee due before issuance of building permit

$1,000.00 $2,000.00

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Current fees (as of 2013)Additional fees Land disturbance

≤10,000sfLand disturbance ≥10,000sf

Field visit for soil percolation test $300 for ≤ 10 borings; $600 for > 10

Review of soil percolation test report $150.00

Soil characteristics inquiry $150.00

Review of geotechnical report $70.00/hour

After-hours inspection fee $50.00/hour

Stormwater pollution plan review $1,100.00

Dewatering pollution reduction plan review $1,100.00 $2,100.00

Application for relief from extraordinarily difficult site conditions

$500.00 $1,000.00

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Current fees (as of 2013)SWMP Review to create retention capacity for Department certification of stormwater retention credits

Land disturbance ≤10,000sf

Land disturbance ≥10,000sf

Initial plan review due upon filing $575.00 $850.00

Final plan review due before issuance of building permit

$125.00 $200.00

Supplemental review fee due before issuance of building permit

$500.00

Review of Green Area Ratio plan Land disturbance ≤10,000sf

Land disturbance ≥10,000sf

Initial plan review due upon filing $575.00 $850.00

Final plan review due before issuance of building permit

$125.00 $200.00

Supplemental review fee (for reviews after first re-submission)

$500.00

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EPA filings

• Filing a Notice of Intent Form with US EPA is required if the project will disturb 1 or more acres of land, or part of a common plan of development or sale that will ultimately disturb 1 or more acres of land must file.

• Consult US EPA’s web site for details, http://cfpub.epa.gov/npdes/stormwater/application_coverage.cfm

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Inspection Requirements

• Prior to SWMP approval, applicant must submit a proposed construction and inspection control schedule

• Stages:– Pre-construction meeting with DDOE– Inspections during construction– Final inspection after construction– Maintenance inspections

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Pre-construction meeting

• Required before beginning land disturbance or installing any BMPs

• Contact DDOE 3 days prior to starting construction

• Submit material certifications for aggregate, soil media, and geotextiles

• Site visit to confirm drainage area, inlet elevations

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Construction inspections

• Contact DDOE 3 days before starting construction of BMPs

• Certifying PE must accompany inspectors at on-site inspections

• The following detail construction inspection schedule for bioretention

• See the Guidebook for inspection schedules for other BMPs

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Bioretention Construction Inspection Checklist

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Construction inspections

• During percolation/infiltration tests

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Construction Inspections

• Upon completion of stripping, stockpiling, and construction of temporary sediment control and drainage facilities

Photo Courtesy of DDOT.

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Construction inspections

• Upon completion of excavation to subgrade

Photo Courtesy of Rasma Plato

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Construction inspections

• During the placement of: – perforated PVC/HDPE standpipes (for

observation wells) including bypass pipes (where applicable)

– geotextile materials– gravel, or crushed stone course– backfill

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Construction inspection

• Upon completion of final grading and establishment of permanent stabilization

Photo Courtesy of DDOT

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Final Inspection

• A final inspection must be conducted by the DDOE upon completion of the BMP to determine if the completed work is constructed in accordance with approved plans

• Contact DDOE to schedule a final inspection 1 week prior to the completion of a BMP construction to schedule inspection

• PE is required to certify “As-Built" plans that the BMP has been constructed in accordance with the approved plans and specifications

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Maintenance inspections

• Performed by DDOE• Twice per year for the first five years• Once every three years thereafter• Maintenance inspection forms are

provided in the Guidebook

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Review

• Construction activities disturbing more than 5,000 square feet of built or landscaped space require submission of a Stormwater Management Plan (SWMP) when applying for a building permit

• New rules require retention of runoff from small storms

• SWMPs must include construction and maintenance schedules

• Certification requires multiple inspections during construction and ongoing maintenance inspections

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Resources

• 2013 District of Columbia Stormwater Management Guidebook (http://ddoe.dc.gov/swregs)

• District of Columbia Soil Erosion and Sediment Control Handbook (http://ddoe.dc.gov/soil-erosion-and-sediment-control-handbook)