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]

This page was last edited on 13 April 2020, at 17:53.

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