Stormwater By-laws Getting Town Buy-in & Approval Nora Loughnane Recharging First One Inch Runoff Phil Paradis Implementing Westwood Stormwater By-law Karon Skinner Catrone Workshop Presentation December 9, 2015
Stormwater By-laws Getting Town Buy-in & Approval of Westwood’s New Stormwater Bylaw Nora Loughnane Director of Economic Development, Town of Westwood Workshop Presentation December 9, 2015
Stormwater Management Bylaw Adoption Formed Stormwater Committee Town Engineer Building Commissioner Town Planner Conservation Agent Engaged Phil Paradis of BETA Group, Inc. Reviewed current drainage systems. Consulted with NepRWA. Discussed mandate, goals, strategies, and limitations.
Stormwater Management in New Development and Redevelopment (Post Construction Stormwater Management) Objective: To reduce the discharge of pollutants found in stormwater through the retention or treatment of stormwater after construction on new or redeveloped sites. a. Permittees shall develop, implement, and enforce a program to address post-construction stormwater runoff from all new development and redevelopment projects that disturb one or more acres and discharge into the permittees MS4 at a minimum.
Current Drainage Systems No Treatment of Runoff Direct Discharge of Pollutants to Water Degrade Water Resources Every Event Do not meet current Stormwater Management Requirements
Thresholds Higher than Minimum 70% to Neponset River impaired for: TSS, Turbidity, E. coli, Dissolved Oxygen, Sedimentation/Siltation, PCB in fish, DDT 30% to Charles River impaired for: Phosphorus (TMDL), E. coli, Nutrients, PCB in fish, DDT & others DWWD Wells – Westwood Water Supply
Established Permit Thresholds No Permit Required if <5,000 sq. ft. of disturbance Administrative Land Disturbance Permit >5,000 sq. ft. but <21,780 Land Disturbance Permit >21,780 and not otherwise subject to ConCom review
Multiple Public Presentations Westwood Planning Board Conservation Commission Board of Selectmen Finance & Warrant Commission Focused on “Why?” Explained mandate. Emphasized shared responsibility, cost effectiveness, and efficiency of process. Provided concrete examples.
Stormwater Management Should I care? What’s all the fuss? Are there problems now? Another permit? Why should I pay?
Development/Stormwater Impacts to Water Quality Development Reduce Vegetation Increase Impervious Reduce Natural Treatment Increase Runoff Degraded Water
Understand the Reality Stormwater Runoff Includes Sand & salt for winter snow/ice treatment Soil from un-stabilized areas Twigs, leaves and mulch Cigarette butts, wrappers and other trash Petroleum & metals from cars and trucks Fertilizers from yards/lawns Detergents from car washing Fecal matter from pets & birds
Water Quality Without BMPs, everything that can be suspended or conveyed in stormwater runoff ends up in water resource systems (wetlands, lakes, rivers and ocean).
Example 1 Modest Single Family Home 30’x50’ House = 1500± sq. ft. 12’x40’ Driveway = 500± sq. ft. 30’x20’ Front Yard = 600± sq. ft. 30’x50’ Rear Yard = 1500± sq. ft. 30’x10’ Side Yards (2) = 600± sq. ft. Total Disturbed Area = 4700± sq. ft. <5,000 sq. ft. = No Permit Required
Example 2 Larger Single Family Home 40’x50’ House = 2,000± sq. ft. 12’x60’ Driveway = 700± sq. ft. 50’x30’ Front Yard = 1,500± sq. ft. 60’x100’ Rear w/ Pool = 6,000± sq. ft. 40’x25’ Side Yards (2) = 2,000± sq. ft. Total Disturbed Area = 12,200± sq. ft. >5,000 sq. ft. but <21,780 = Administrative Permit Required
Town Meeting Article Favorable recommendations from: Westwood Planning Board Conservation Commission Board of Selectmen Finance & Warrant Commission Presentation in cue. Not needed. Minimal discussion. Unanimous vote for adoption !
Stormwater By-laws Recharging First One Inch Runoff Phil Paradis, PE, LEAD AP , CPSWQ BETA Group, Inc. Consultant to Town of Westwood Workshop Presentation December 9, 2015
New Stormwater Technology M agical E nvironmentally S ensitive S olution (MESS) Patent Pending (Not really)
MESS – Solution For All Projects Areas: Urban, Suburban, Rural & Campsite Areas Uses: Agriculture, Residential, Commercial, Industrial, Institutional, DPW Yards & Nuclear Facilities Works with Terrain and Topography Compatible with all Wetland, Riverfront, ACEC, NHESP, FEMA, Chapter 91 and FDA Regulations Abutters: Love it - produces no noise, odors or taxes
MESS – SW Solution For Project Requires no Space & Fits All Size Sites Attenuates Peak Runoff for 2, 10, 100 & Armageddon Year Storm Events Accommodates All Soils (A-D & Bedrock) Recharges first 7 inches of rainfall without flooding adjacent basements Groundwater Considerations: not necessary Perfect Retrofit for Redevelopments Maintenance can be performed via email
Unfortunately For Stormwater Engineers & Regulators there is no M agical E nvironmentally S ensitive S olution But an ever increasing challenge to address Stormwater Impacts for Past, Present and Future Development Projects
Stormwater Management in New Development and Redevelopment (Post Construction Stormwater Management) 2.3.6.a.ii.(a)Stormwater management systems on new and re-developed sites shall be designed to either: Retain the first one (1) inch of runoff from all impervious surfaces on site. OR Provide the level of pollutant removal equal to or greater than the level of pollutant removal provided through the use of biofiltration on the first one (1) inch of runoff from all impervious surfaces on site. This standard shall be met through a combination of practices designed to retain runoff on site (environmentally sensitive site design, low impact development techniques) where technically feasible, and stormwater BMPs designed to treat the remainder of runoff that cannot be retained on site due to site constraints.
To Retain 1 Inch SMP Must Consider Development Area & Uses Site Topography Applicable Regulations Impacts to Abutters Available Space & Site Size Peak Runoff impacts Connected & Disconnected Impervious Area Suitability of Soils & Groundwater Elev. for Recharge Retrofit for Redevelopments Ease of Inspection and Maintenance
To Retain 1 Inch SMP Must Consider Best Management Practice (BMP) or Low Impact Development (LID) Technique $Costs : Design and Permitting Installation Operation and Maintenance
Infiltration is as close to MESS as it comes Reduces Runoff (Peak Rate & Volume) Promotes Groundwater Percolation Treats Runoff (Nutrients & Pathogens)
Is Site Suitable for Recharge? Determine Characteristics of On-site Soils A - high infiltration rates, well/excessively well-drained sands/gravels. B - moderate infiltration rates, moderately well/well drained soils. C - slow infiltration rates, less draining soils. D - very slow infiltration rates, poorly draining soils Determine Seasonal High Groundwater Elevation Typically 2 ft Separation required BMP bottom to SHGWE Mounding Calculation may be required Consider Other Factors Abutter Impacts Soil Contamination Wellhead Protection Zone Environmentally Sensitive Areas
Typical BMPs for Sites > 1 Acres Infiltration Systems Retention/Infiltration Basin Extended Dry Detention Basin Subsurface Infiltration System Infiltration Trench
Typical BMPs for Sites > 1 Acres Wetland/Treatment Systems Constructed Stormwater Wetland Water Quality Swale Wet/Dry Bioretention Basin (Rain Garden) Gravel Wetland Wet Basin Sand or Organic Filter Proprietary Media Filter
For Sites < 1 Acres Low Impact Development (LID) Techniques Disconnect Impervious Area, Address Runoff at Source & Small Recharge Areas Spread Throughout Site Residential Lot Techniques Commercial Lot Techniques • Porous driveways or • Porous parking areas • Slope driveways to lawn • Rain Gardens as landscaping features • Rain gardens at low areas • Curb cuts • Maintain existing treeline • Drywells for roof runoff • Rain barrels and drywells • Tree Box Filters • Green Roofs
Commonwealth Ave Boston (~1.1 mile) Stormwater Management Challenges Required to Meet TMDL for Charles River No Available Land Outside Right of Way for BMPs Significant Utilities in Road/ROW Limited Outlet Connections Recharge 1 inch Reduced to 65% Phosphorus Removal (0.3 inch per soils)
Commonwealth Ave Boston Design Incorporated Retrofitting Existing System Leaching Catchbasins Leaching Manholes Leaching Chambers Leaching Pipe (Trench) Systems
Commonwealth Ave Boston
Commonwealth Ave Boston
Pine Street Natick (~1 mile) Stormwater Management Challenges Non-existent/Undersized Drainage System Existing Flooding Problems Adding Impervious (5.5’ New Sidewalk) Adding Curb No Available Land Outside Right of Way for BMPs Limited Outlet Connections
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