Site considerations
From LID SWM Planning and Design Guide
(Redirected from LID site criteria and constraints)
| Installation type | Depth to high water tableThe upper surface of the zone of saturation, except where the surface is formed by an impermeable body.Subsurface water level which is defined by the level below which all the spaces in the soil are filled with water; The entire region below the water table is called the saturated zone. or bedrock (m)[1] | Typical ratio of ImperviousA hard surface area (e.g., road, parking area or rooftop) that prevents or retards the infiltration of water into the soil. drainage areaThe total surface area upstream of a point on a stream that drains toward that point. Not to be confused with watershed. The drainage area may include one or more watersheds. to treatment facility area |
Native soilThe natural ground material characteristic of or existing by virtue of geographic origin. infiltration rateThe rate at which stormwater percolates into the subsoil measured in inches per hour. (mm/hr)[2] | Head (m)[3] | Space % [4] | Slope % [5] | Applicable in pollution hotspots [6] | Set backs | Karst[7] | Wellhead protection area[8] |
|---|---|---|---|---|---|---|---|---|---|---|
| Rain Barrel | Not applicable | 5 to 50 m2 | Not applicable | 1 | 0 | NA | Yes | None | Yes | None |
| Cistern | Not applicable | 1:1 | Not applicable | 0 | 0 | 0 | Yes | None | Yes | None |
| Roof downspout disconnection | Not applicable | 5 to 100 m2 | Amend if < 15 mm/hr | 0.5 | 5 to 20 | 1 to 5 | Yes | Building Foundation | Yes | None |
| Infiltration trenches or Infiltration chambers | 1 | 5:1 to 20:1 | Not a constraint | 1 to 2 | 0 to 1 | <15 % | No | 4m- Building Foundation Underground Utilities, Trees, Drinking Water Wellhead Protection Areas |
No | 2 yr |
| Bioretention | 1 | 5:1 to 15:1 | Underdrain recommended if < 15 mm/hr |
1 to 2 | 5 to 10 | 0 to 2 | No (infiltrating); Yes (non-infiltrating) | 4m- Building Foundation Underground Utilities, Trees, Drinking Water Wellhead Protection Areas |
No (infiltrating); Yes (non-infiltrating) | 2 yr (infiltrating); None (non-infiltrating) |
| Stormwater planters | Not applicable | 5:1 | Not a constraint | 1 to 2 | 2 to 5 | 0 to 2 | No (infiltrating); Yes (non-infiltrating) | Building Foundation, Trees | No (infiltrating); Yes (non-infiltrating) | 2 Yr (infiltrating); None (non-infiltrating) |
| Vegetated filter strips | Not applicable | 5:1 | Amend if < 15 mm/hr | 0 to 1 | 15 to 20 | 1 to 5 | No | None | Yes | None |
| Permeable pavements | 1 | 0:1 to 1:1 | UnderdrainA perforated pipe used to assist the draining of soils. recommended if < 15 mm/hr |
0.5 to 1 | 0 | 1 to 5 | No (infiltrating); Yes (non-infiltrating) | 4m-Underground Utilities Drinking Water Wellhead Protection Areas |
No (infiltrating); Yes (non-infiltrating) | 2 Yr (infiltrating); None (non-infiltrating) |
| Enhanced swales (has checkdams) | Not applicable | 5:1 to 10:1 | Not applicable | 1 to 3 | 5 to 15 | 0.5 to 6 | No | 4m- Building Foundation Underground Utilities |
Yes | None |
| Dry swale (BioswaleLinear bioretention cell designed to convey, treat and attenuate stormwater runoff. The engineered filter media soil mixture and vegetation slows the runoff water to allow sedimentation, filtration through the root zone, evapotranspiration, and infiltration into the underlying native soil.) | 1 | 5:1 to 15:1 | UnderdrainA perforated pipe used to assist the draining of soils. recommended if < 15 mm/hr |
1 to 3 | 5 to 10 | 0.5 to 6 | No (infiltrating); Yes (non-infiltrating) | 4m (3m if impermeable liner is used) Building foundation, Underground utilities, Drinking Water Wellhead Protection Areas |
No (infiltrating); Yes (non-infiltrating) | 2 Yr (infiltrating); None (non-infiltrating) |
| Exfiltration trenches | 1 | 5:1 to 10:1 | Not a constraint | 1 to 3 | 0 | < 15% | No | 4m- Building Foundation Underground Utilities, Trees, Drinking Water Wellhead Protection Areas |
No | 2 Yr |
- ↑ Minimum depth between the base of the facility and the elevation of the seasonally high water table or top of bedrock
- ↑ Infiltration rate estimates based on measurements of hydraulic conductivity under field saturated conditions at the proposed location and depth of the practice
- ↑ Vertical distance between the inlet and outlet of the LID practice
- ↑ Percent of open pervious land on the site that is required for the LID practice
- ↑ Slope at the LID practice location
- ↑ Suitable in pollution hot spots or runoff source areas where land uses or activities have the potential to generate highly contaminated runoff
- ↑ Suitability in areas of karst geologic formations
- ↑ | Drinking Water Source Protection wellhead protection area time of travel
