Above ground and below grade storage and settling - system design information
Above ground and below grade storage and settling - system design information
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| Device | Drainage area | Entrance/exit velocity | Dimensions | Materials | Layout Recommendations (physical location, off-line placement) | Soils |
|---|---|---|---|---|---|---|
| Pretreatment row on underground storage/filtration | Varies widely, units may be placed in parallel and series to accommodate | Varies. Limiting factor is site footprint available. | Rigid chamber, gravel | In-line, ideal under parking lots and areas with tight footprints | Ideally highly infiltrative to achieve volume reduction | |
| StormTech Isolator Row | Varies widely, units may be placed in parallel and series to accommodate | See flow Table 2 | Max length of row = 175 ft, but multiple rows may be used, see dimensions table for models SC-310, SC-310-3, SC-780, MC-3500 and MC-4500 [1] | Two layers of woven geotextile, StormTech chamber, non-woven fabric if model has perforated side walls, gravel [2] | In-line, after a manhole with a high flow weir. System is ideal under parking lots and roadways and areas with tight footprints [3] | Ideally highly infiltrative to achieve volume reduction [4] |
| Settling chamber/vault | Can accommodate most drainage areas for downstream BMP [5] | Exit velocity to surface media filters should be non-erosive [6] | Recommended length to width ratio of 2:1 | |||
| Oil/water/grit separators | <1 acre impervious cover [7] | 1-3 ft/min or less [8] | Total wet storage = 400 cf per acre of contributing imp area, depth of permanent pool >4 ft [9] | Reinforced concrete | Off-line, ideal in urban areas with small lots and for retrofits [10] | No soil or terrain restrictions [11] |
| Hydro Dry Screen | Max Flow: 29-162 cfs, Treatment Flow: 11-80 cfs , 80% TSS removal: 1.8-16 cfs [12] | Five models: 4x8 ft to 12x20 ft (see Table 1) [13] | New construction or redevelopment sites, retrofit of storm drain lines, shallow installations with high groundwater or bedrock, installations requiring low headloss [14] | |||
| Suntree Nutrient Seprating Baffle Box (NSBB) | Maximum Treatment Flow Rate: 2-45 cfs [15] | 4 ft x 2 ft x 2.7 ft - 24 ft x 12 ft x 9 ft [16] | Online [17] | |||
| Manhole Baffle Box | 1-100 acres [18] | Typically 10-15 ft long x 6-8 ft high x 2 ft wider than pipe [19] | Concrete, fiberglass [20] | In-line or at the end of storm pipes, ideal for retrofitting existing pipes [21] | ||
| Environment 21 StormPro | 0.5-8.6 cfs. Max loading for all models = 10.8 gpm/sq ft [22]; [23] | 11 models. The 5 models in the StormPro V series range from 4 ft x 8 ft x 2.5+ ft to 10 ft x 20 ft x 5+ ft [24]; [25] | Baffle wall: precast concrete or other approved rigid materials, Bypass pipe: rigid plastic [26] | |||
| BaySeparator by BaySaver | 1.2-8 acres impervious area [27] | Treats maximum of 22 cfs [28] | 5 standard sizes: manhole diameter 48-120 inches, 6-8 ft deep [29] | Concrete, HDPE, polyethylene [30] | ||
| Sump Manhole with SAFL Baffle | <10 acres [31] | Horizontal flow must be at least 3x flow from above [32] | Can be installed in sump structures w/ diameters of 3-10 ft and depths >= 3 ft [33] | Stainless steel [34] | New or existing sump manhole [35] | |
| Deep sump catch basin | <0.25 acre impervious area | < 3 cfs [36] | Diameter of outlet pipe = D: diameter of catch basin = 4D, sump depth >= 4D, top of outlet pipe 1.5 D below bottom of inlet. Minimum sump depth = 4 ft. [37] | Off-line system. May not be used in place of oil/grit separator or sand filter in areas with potential to generate high concentrations of oil and grease such as high-use parking lots, gas stations, and vehicle storage areas [38] | ||
| Forebay/pre-settling | 10 acres minimum to wet pond, portion feeding into forebay depends on number of tributaries to pond [39] | ~0.2 cfs/acre drained [40] | Volume > 10% of water quality volume, depth = 3-6 ft, surface area = 10% of pond permanent pool surface area or 0.1% of drainage area, Tear shaped (inlet at narrow end) w/ avg length to width ratio = 3:1, side slope = 3:1 or flatter [41]; [42] | Bottom of forebay hardened using concrete, asphalt, or grouted riprap [43] | On-line, at each inlet contributing greater than 10% of the total design storm inflow to pond [44] | Underlying soils should be hydrologic group C or D, liner may be needed for A or B group soils. [45] |