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Low Impact Development Stormwater Controls and Changing State and
Federal Regulations
Steven Roy, LEED® AP
Geosyntec Consultants, Inc. Acton, MA
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Presentation Objectives• Understanding of the new regulatory drivers for
innovative stormwater management including Infiltration and groundwater recharge
• Energy Independence and Security Act Section 438 requirements, and Executive Order 13514
• Discuss examples of Low Impact Development (LID) stormwater implementation including techniques such as porous pavers, porous asphalt, bioretention, raingardens, and dry wells
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www.epa.gov/owow/nps/lid/section438
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Impervious Surfaces Generate Stormwater Runoff
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Low Impact Development (LID)
An ecosystem-based approach to land development and stormwater management
Mimic pre-development site hydrology
Low Impact Development Centerwww.lowimpactdevelopment.org
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Conventional vs. LID Approach to Stormwater
• Conventional Collect Convey Discharge
• LID Approach Reduce volume Minimize impacts Distributed controls Treatment trains Infiltration Hybrid systems Mimic the
predevelopment hydrology
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What are the Drivers for Innovative Stormwater and Ground Water Recharge?
• Energy Independence and Security Act of 2007 (EISA)- Federal Facilities
• LEED/Green Design• State Stormwater Regulations• New Municipal Separate Stormwater
System (MS4) Stormwater Permits
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New Terminology for Stormwater in Permits and Regulations
• Mimic Pre-development Hydrology• Retain onsite• Maximize Infiltration• Groundwater Recharge Requirements
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EISA Section 438
Text of Section 438:
“Storm water runoff requirements for federal development projects. The sponsor of any development or redevelopment project involving a Federal facility with a footprint that exceeds 5,000 square feet shall use site planning, design, construction, and maintenance strategies for the property to maintain or restore, to the maximum extent technically feasible, the predevelopment hydrology of the property with regard to the temperature, rate, volume, and duration of flow.”
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Maximum Extent Technically Feasible (METF)
• Stormwater control practices that are effective in reducing the volume of stormwater discharge must be used.
• The Federal facility must use all known, available and reasonable methods of stormwater retention and/or reuse to prevent the off site discharge of stormwater runoff consistent with the performance standard.
• In cases when a facility seeks or claims an exception, it is expected that there will be a serious and documented attempt to comply.
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Performance Options
Option 1 : Control 95th Percentile Rainfall Event •Manage rainfall onsite•Infiltrate, Evapotranspirate, Harvest and
Infiltrate, and Reuse Runoff
Note: The 95th percentile rainfall event is the event whose precipitation total is greater than or equal to 95 percent of all 24-hour storms on an annual basis.
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95% Storm Event
City 95th Percentile Event Rainfall Total (in) City
95th Percentile Event Rainfall Total (in)
Atlanta, GA 1.8 Kansas City, MO 1.7Baltimore, MD 1.6 Knoxville, TN 1.5Boston, MA 1.5 Louisville, KY 1.5
Buffalo, NY 1.1 Minneapolis, MN 1.4Burlington, VT 1.1 New York, NY 1.7
Charleston, WV 1.2 Salt Lake City, UT 0.8
Coeur D’Alene, ID 0.7 Phoenix, AZ 1Cincinnati, OH 1.5 Portland, OR 1Columbus, OH 1.3 Seattle, WA 1.6Concord, NH 1.3 Washington, DC 1.7Denver, CO 1.1
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Worst case cost
52,272 sq ft @ $15/sq ft = $784,080
Plus site demo, design, permits= ~$900k
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Performance Options
• Option 2: Preserve predevelopment hydrology (rate, volume, duration & temperature) Conduct hydrologic and hydraulic analyses Quantify post-construction hydrographs for the following storm
sizes: • 1, 2, 10 and 100 year 24 hour storm events
Maintain pre-development hydrographs for these storm events
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Performance Options
What if Options 1 and 2 are not technically feasible?
• Conduct site evaluation and assessment • If site conditions or other factors preclude
achievement of Options 1 or 2, i.e., neither is technically feasible
• Agency/Department follows a process to employ onsite practices to the METF
• Agency/Department documents stormwater design based on METF and other factors
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Complying with EISA
• Executive Order 13514, Federal Leadership in Environmental, Energy, and Economic Performance, Oct 5, 2009: Required EPA to Issue Guidance
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www.epa.gov/owow/nps/lid/section438
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DOD - EISA Implementation Policy
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New Proposed Federal and State Stormwater Regulations
• EPA Proposed new SW Rulemaking – Effective Nov 2012 New stormwater controls for “newly developed and redeveloped sites” Recently completed “listening” sessions EPA sent out an ICR (Information Collection Rule) to developers, MS4
permit holders, and states Likely to require retrofits to existing sites
• New – North Coastal Watersheds MS4 Permit - Massachusetts 84 Communities and several state/federal and transportation agencies Requires compliance with new MA SW Management Standards for post
construction stormwater control Requires as-built plans for all new development to demonstrate
compliance Requires elimination of local barriers to green infrastructure Requires GW recharge and infiltration where feasible – first 1 Inch Requires an assessment of street design & parking lot guidelines and other
requirements that create impervious cover
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LID BMP Performance Metrics (Ventura and Orange County, CA)
• Retain (infiltrate, harvest and use, or evapotranspire) or biotreat the runoff volume from the 85th percentile, 24-hour storm event (“design capture volume”) on-site to the Maximum Extent Practicable (MEP)
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Effective Impervious Area Metric (Ventura County, CA)
• Projects must reduce Effective Impervious Areato less than 5% of the total project area
• Impervious surface are rendered “ineffective” if water quality design storm runoff volume is fully retained onsite 85th percentile, 24-hour event 80 percent capture volume 0.75 inch storm event
• Any remaining surface discharges must be treated
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Draft District of Columbia MS4 Permit• Integrate green technology stormwater
management practices at the site and neighborhood level through policies, regulations, ordinances and incentive programs
• Mimic pre-development site hydrology through use of on-site stormwater retention measures (e.g., harvesting and using, infiltration and ET)
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Draft DC MS4 Permit
• Performance standards: On-site retention of 1.2 in. (non-federal) or 1.7
in. (federal) from a 24- hour storm with a 72-hour antecedent dry period
Retention of the predevelopment runoff volume of stormwater from a 24- hour storm with a 72-hour antecedent dry period• Maintenance of predevelopment hydrographs
(volume, rate and duration) for the 1-, 2-, 10- and 100-year 24-hour storm events.
• Modeled predevelopment condition must be meadow.
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MA Stormwater Standards• the annual recharge from the post-development
site shall approximate the annual recharge from pre-development conditions based on soil type.
• capture of at least the 1 inch (90th percentile) storm event.
• The term “capture” includes practices that infiltrate, evapotranspire, and/or harvest and reuse rainwater. This means that 100 percent of the volume of water from events less than or equal to the 90th percentile event shall not be discharged.
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Pennsylvania Stormwater BMP Manual – Volume Control
• At least the first one inch (1.0”) of runoff from new impervious surfaces shall be permanently removed from the runoff flow — i.e. it shall not be released into the surface Waters of this Commonwealth.
Removal options include reuse, evaporation, transpiration, and infiltration.
• Wherever possible, infiltration facilities should be designed to accommodate infiltration of the entire permanently removed runoff; however, in all cases at least the first one-half inch (0.5”) of the permanently removed runoff should be infiltrated.
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EPA Class V/Stormwater Memo-2008
•Infiltration Trenches
•Commercially Manufactured Stormwater Infiltration Devices
•Drywells, Seepage Pits, ImprovedSinkholes
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Dry Wells and UIC Class V
States require registration – Is it happening?Leaching catch basins in roadways- State and Local DOT’s?
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Sustainable Stormwater Management• Low Impact Development Stormwater Designs Green roofs Trees and tree boxes Raingardens/bioretention/infiltration planters Vegetated swales Pocket wetlands Permeable pavements Reforestation/revegetation Site planning- protection of riparian
buffers/floodplains Rainwater harvesting/reuse (where allowed)
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Tree Box Filters/Roof Top Planters
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LID Design Feature
Planter Box Bioretention Cell• Treat roof top drainage • Reduce storm water volume• Decrease peak discharge• Provide high levels of pollutant
removal
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Porous Surfaces
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LID Design Feature
Porous Pavers• Surface with "holes" which can be
filled with vegetation or aggregate depending upon the need.
• Porous pavers provide the same advantages as traditional concrete pavers, including resistance to heavy loads, flexibility of repair, low maintenance, exceptional durability, and high quality.
• Use infiltration to reduce stormwater runoff that leaves parking lots
• Increase stormwater storage • Reduce thermal loading on surface
waters • Reduce pollutants reaching surface
waters
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US Navy Monterey Post Graduate Naval AcademyInstalled 30,000 Square Feet of Permeable Pavers Photo Credit: Belgard Pavers
LID Opportunities
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Drivable Grass®
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FlexiPave™ – recycled rubber tires and aggregate
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Porous Asphalt
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Porous Concrete
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Bioretention Cells
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LID Design FeaturesBioretention Cell• Provide water quality treatment; remove suspended solids,
metals, nutrients • Increase groundwater recharge through infiltration • Reduce peak discharge rates • Reduce total runoff volume • Improve site landscaping
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100 ft Bioretention Cell in Parking Lot
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Leadership in Energy and Environmental Design -LEED® and
Stormwater Management
Green Building- GSA Has a “Zero Environmental Footprint” Goal
Green Infrastructure- Promoting LID and Pre-Development Hydrology
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Summary – the New Stormwater • Federal Requirements for Green Design and EISA Section
438 are mandating stormwater infiltration- Guidance• Most requirements require capture and onsite infiltration of
between 1.0 -1.5+ inches of runoff from impervious surfaces• New stormwater regulatory terminology
Mimic the pre-development hydrology Retain onsite Infiltrate stormwater to the maximum extent practicable
(MEP) Federal Facilities -Maximum Extent Technically Feasible
(METF)• UIC Class V Well registration may be required-
Compliance?
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Questions?
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