Natural Treatment of Stormwater
B3Natural Treatment of Stormwater
8 points possible
Why this matters to the lake?
The healthy, forested landscape that is native to Lake George acts like a sponge when it rains, absorbing rainfall and filtering the water through the soils to remove pollutants, actions crucial to keeping the lake clean and clear. A healthy forest with mature trees, understory, and leaf litter will absorb nearly all rain that falls except from the largest and most intense storms. Mature vegetation with deep roots promotes infiltration and natural uptake. Stormwater storage provided by natural depressions can attenuate runoff and facilitate vernal pool establishment.
Natural treatment of stormwater is achieved by first protecting natural landscape features, followed by reducing the amount of runoff coming from impervious surfaces and lawns. Where impervious areas are necessary, implement practices to capture and retain rainfall before it becomes runoff close to the building or pavement it comes from; fundamental to stormwater management is treating stormwater runoff at the source. The following methods enable stormwater to be managed and treated close to its source:
- Reduce runoff by disconnection
- Direct drainage from lawns and impervious areas toward on-site landscaped areas
- Disconnect downspouts onto pervious areas
- Avoid discharging runoff onto steeply sloped areas or adjacent impervious areas
- Use Infiltration and biological treatment
- Use vegetated swales and filter strips
- Construct at the existing grade and do not build on fill.
- Implement bioretention and rain gardens to promote biological treatment with soils and vegetation
- Incorporate Stormwater Infiltration Beds, including Stormwater Tree Trenches, Infiltration Beds beneath pervious pavements, and Dry Wells
- Spread stormwater controls throughout site (close to source) to limit conveyance.
- Increase time of concentration (Tc)
- Increase time of concentration by using longer flow paths
- Intentionally direct small amounts of runoff towards natural depressions in the landscape
- Up to two points are awarded for reducing runoff by disconnection.
- Up to one point is awarded for using infiltration.
- Up to two points are awarded for using vegetated treatment systems.
- Up to two points are awarded for spreading stormwater controls throughout site (close to source) limiting conveyance.
- One point is awarded for increasing time of concentration (Tc).
Redevelopment Prerequisite: Redevelopment projects shall require stormwater management for all existing and proposed impervious surfaces. Management requirements are 1.5 gallons per square foot of impervious area.
Note: If the stormwater from a portion of a project area cannot be captured due to topography or other constraints, the project may propose an alternative, such as managing stormwater from a nearby existing impervious surface subject to the same criteria as above.
Include the following information with application:
- As part of the Proposed Site plan:
- Provide a narrative and supporting calculations that document disturbed area, impervious area, volume of runoff and compliance with Lake George Park Commission regulations.
- Provide a narrative and supporting calculations that indicate time of concentration (Tc), the drainage area and impervious area managed by a stormwater measure.
- Show the appropriate stormwater control measures as well as stormwater permit from the Lake George Park Commission if in the Town of Putnam, Hague, Dresden, Fort Ann or Ticonderoga, or a permit from the Town of Lake George, Bolton, Queensbury, or Lake George Village.
- Document that stormwater measures are:
- Not located on steep or very steep slopes.
- Not located within a stream, wetland, or lake setback area.
- Will not result in the removal of native trees over 4-inch caliper.
- "New York State Stormwater Management Design Manual (August, 2010)." New York State Department of Environmental Conservation, Web.
- "Pennsylvania Stormwater Best Management Practices Manual." Pennsylvania Department of Environmental Protection, Web.
- "Rain Garden Design Templates - How to Design a rain garden." Low Impact Development Center.
- “Best Ways to Deal with Storm Water." This Old House.
- “The Vermont Rain Garden Manual.” University of Vermont.
- "How to Build a Rain Garden, Philadelphia Water Department." Philadelphia Water Department.
- "Native Plants for Rain Gardens." The Lake George Association in New York. Web.
- Planting Design & Plants Database – United States Department of Agriculture – Natural Resources Conservation Service
- Wetland Planting Guide for the Northeast United States. Native Trees, Shrubs, and Vines for Urban and Rural America.
Existing Regulatory Guidance/Requirements
Lake George Park Commission, Part 646-4 – Stormwater Management
Town of Queensbury Town Code Chapter 147 - Stormwater Management.
Lake George Town Ordinance, Chapter 175-21- Erosion, sedimentation and stormwater runoff control.
Lake George Village Ordinance, Chapter 220 - Article IX - Stormwater Management Regulations
Bolton Town Ordinance, Chapter 125 – Stormwater and Erosion Control