Above ground and below grade storage and settling - pollutant removal information

Above ground and below grade storage and settling - pollutant removal information
Link to this table

Device Primary mechanism Secondary mechanism Other mechanism Proprietray/nonproprietray Above ground/below grade Pollutants removed
Pretreatment row on underground storage/filtration Settling Screening/straining Infiltration (for volume loss) Nonproprietary Below grade Sediment, total suspended solids
StormTech Isolator Row (see adjacent figure) [1] Settling Screening/straining Infiltration (for volume loss) Proprietary Below grade Sediment, total suspended solids (>110 µm)
Settling chamber/vault Settling Nonproprietary Below grade Sediment
Oil/water/grit separators Settling Screening/straining Nonproprietary Below grade Trash and debris, floatables, oil and grease, coarse sediment, total suspended solids when placed off-line [2]; [3]
Hydro Dry Screen Settling Screening/straining Buoyancy/skimming Proprietary Below grade Total suspended solids, oils, gross debris, nutrients [4]
Suntree Nutrient Separating Baffle Box (NSBB) Settling Screening/straining Buoyancy/Skimming; Biodegradation; Filtration (SkimBoss option) Proprietray Below grade Total suspended solids, nutrients, organics, trash, litter, oils and grease [5]
Manhole Baffle Box Settling Screening/straining Nonproprietary Below grade Sediment, suspended solids, trash, floatables [6]
Environment 21 StormPro Settling Proprietary Below grade Suspended solids, hydrocarbons, trash, floatables [7]
BaySeparator by BaySaver Settling Buoyancy/skimming Proprietray Below grade Sediment, floatables, oil
Sump Manhole with SAFL Baffle Settling Screening/straining Proprietray Below grade Sands and large silt sediment, total suspended solids
Deep sump catch basin Settling Buoyancy/skimming Nonproprietary Below grade Sediment, debris, trash, oil
Forebay/pre-settling basin for wet pond Settling Nonproprietray Aboveground Sediment


Above ground and below grade storage and settling - system design information

Above ground and below grade storage and settling - system design information
Link to this table

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 [8] Two layers of woven geotextile, StormTech chamber, non-woven fabric if model has perforated side walls, gravel [9] In-line, after a manhole with a high flow weir. System is ideal under parking lots and roadways and areas with tight footprints [10] Ideally highly infiltrative to achieve volume reduction [11]
Settling chamber/vault Can accommodate most drainage areas for downstream BMP [12] Exit velocity to surface media filters should be non-erosive [13] Recommended length to width ratio of 2:1
Oil/water/grit separators <1 acre impervious cover [14] 1-3 ft/min or less [15] Total wet storage = 400 cf per acre of contributing imp area, depth of permanent pool >4 ft [16] Reinforced concrete Off-line, ideal in urban areas with small lots and for retrofits [17] No soil or terrain restrictions [18]
Hydro Dry Screen Max Flow: 29-162 cfs, Treatment Flow: 11-80 cfs , 80% TSS removal: 1.8-16 cfs [19] Five models: 4x8 ft to 12x20 ft (see Table 1) [20] New construction or redevelopment sites, retrofit of storm drain lines, shallow installations with high groundwater or bedrock, installations requiring low headloss [21]
Suntree Nutrient Seprating Baffle Box (NSBB) Maximum Treatment Flow Rate: 2-45 cfs [22] 4 ft x 2 ft x 2.7 ft - 24 ft x 12 ft x 9 ft [23] Online [24]
Manhole Baffle Box 1-100 acres [25] Typically 10-15 ft long x 6-8 ft high x 2 ft wider than pipe [26] Concrete, fiberglass [27] In-line or at the end of storm pipes, ideal for retrofitting existing pipes [28]
Environment 21 StormPro 0.5-8.6 cfs. Max loading for all models = 10.8 gpm/sq ft [29]; [30] 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 [31]; [32] Baffle wall: precast concrete or other approved rigid materials, Bypass pipe: rigid plastic [33]
BaySeparator by BaySaver 1.2-8 acres impervious area [34] Treats maximum of 22 cfs [35] 5 standard sizes: manhole diameter 48-120 inches, 6-8 ft deep [36] Concrete, HDPE, polyethylene [37]
Sump Manhole with SAFL Baffle <10 acres [38] Horizontal flow must be at least 3x flow from above [39] Can be installed in sump structures w/ diameters of 3-10 ft and depths >= 3 ft [40] Stainless steel [41] New or existing sump manhole [42]
Deep sump catch basin <0.25 acre impervious area < 3 cfs [43] 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. [44] 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 [45]
Forebay/pre-settling 10 acres minimum to wet pond, portion feeding into forebay depends on number of tributaries to pond [46] ~0.2 cfs/acre drained [47] 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 [48]; [49] Bottom of forebay hardened using concrete, asphalt, or grouted riprap [50] On-line, at each inlet contributing greater than 10% of the total design storm inflow to pond [51] Underlying soils should be hydrologic group C or D, liner may be needed for A or B group soils. [52]


Above ground and below grade storage and settling - system and component sizing

Above ground and below grade storage and settling - system and component sizing
Link to this table

Device Land use Downstream BMP (type) Enhancement opportunity Sizing calculations Inlets/oulets Flow diversion structures
StormTech Isolator Row Residential, Urban, Commercial StormTech detention/ infiltration arc storage chambers [53] Yes Volume-based for sites with good infiltrative soils, or more commonly rate-based using a water quality flow <= 2.5 gpm/sq ft of bottom area using two layers of woven geotextile, see Table 2. See design tool from manufacturer (does not require registration). [54] Manhole with overflow weir before pretreatment row
Settling chamber/vault Urban, Construction, Agricultural [55] Infiltration, Media Filtration [56]; [57] No Volume equivalent to at least 25% of water quality volume, surface area calculated from flow and particle settling velocity [58] Overflow weir at end of chamber
Oil/water/grit separators Ultra-high density, Industrial, Commercial [59] Yes Size device to pass 2-year 24-hour storm without interference and then provide bypass for larger storms [60] 8-inch diameter minimum [61] Inlet chamber (sediment trapping), oil separation/storage chamber, inverted elbow pipe to bypass chamber [62]; [63]
Hydro Dry Screen Residential, Commercial Yes Rate-based, 80% TSS removal based on 25 gpm/sq ft settling area, treatment flow rate based on 150 gpm/sq ft settling area. Download the manufacturer’s sizing tool here (requires registration) Max pipe diameter = 30-60 in [64] Vertical screen weir [65]
Suntree Nutrient Separating Baffle Box (NSBB) Rainwater harvesting, Wet or dry detention [66] Yes Q = ciA (runoff coeff. * intensity * area), then see Table 1 (NJCAT) [67] See tables for inlet and outlet placement depending on manhole and pipe diameters Three chambers/stages [68]
Manhole Baffle Box Yes Precast boxes: can be used for pipes up to 48 in diameter, up to 60 in if cast in place [69] Weir height = 3 ft, set at same level as pipe invert [70]
Environment 21 StormPro No Rate-based sizing Model V510: inlet/outlet diameter = 15 in diameter [71] Baffle wall, bypass pipe [72]
BaySeparator by BaySaver Yes Rate-based sizing Surface skimming weir, flow to and from offline manhole storage [73]
Sump Manhole with SAFL Baffle Residential, Commercial Yes Sizing with SHSAM [74] Top of SAFL baffle roughly 2-6 in above top of inlet, Sump depth below outlet >= 3 ft, bottom of SAFL baffle at 1 ft below invert of outlet . Max inlet diameter: 15-54 inches Baffle wall [75]; [76]
Deep sump catch basin Residential, Office, Retail [77] No Rate-based sizing, flow not to exceed capacity of inlet grate [78] Outlet below water surface level to allow floatables to remain on top. Inlet 4 ft above water surface level. Hooded outlet to prevent floatable materials and trash from entering storm drain system, weep hole above outlet pipe [79]; [80]
Forebay/pre-settling basin Wet Pond, Storm Water Treatment Wetland [81] No V with 1-2 ac imp area = 0.01* WQV; Max depth = 12 in; V with 2-5 ac imp area = 0.02 * WQV; Max depth = 18 in; V with 5-10 ac imp area = 0.03 * WQV; Max depth = 18 in; V with >10 ac imp area = 0.03 * WQV; Max depth = 24-30 in [82] Size outlet based on avg release rate and average head (elev. diff. between permanent pool water surface elev. and water quality volume elev.), non-erosive conditions. [83]; [84] Rip rap channel, pipe outlet or concrete channel with a notch outlet can be constructed between forebay and downstream practice [85] Anticipate overflow of forebay basin. Adequate protection of downstream structure or berm is necessary along with appropriate erosion control measures. If piped flows are used in the design, minimum recommended pipe diameter is 8 in, and recommended only for larger catchments.


Above ground and below grade storage and settling - installation and maintenance recommendations

Above ground and below grade storage and settling - installation and maintenance recommendations
Link to this table

Device Installation notes Frequency of inspections Maintenance checklist (link) Permitted on private land/ Maintenance agreement recommended Practices for minimizing sediment and trash buildup Practices for minimizing erosion Cost considerations (equipment needed and man hours)
Pretreatment row on underground storage/filtration no data At least every 6 months for first year of operation, then varies by location Periodically remove sediment by back-flushing water and vacuuming manhole sump [86] Vacuum truck
StormTech Isolator Row Installation instructions available here. At least every 6 months for first year of operation, then varies by location [87] Step by step maintenance procedures Clean-out when average depth of sediment exceeds 3 inches [88] Vacuum/JetVac combination vehicle [89]
Settling chamber/vault Remove sediment once depth reaches 6 inches or more [90]
Oil/water/grit separators After every major storm but at least once per month [91] Clean out at least twice per year [92]
Hydro Dry Screen Every 3-6 months during first year, then site specific [93] Maintenance and inspection checklist [94] Remove sediment once depth exceeds maximum clean-out depth [95] Vacuum truck
Suntree Nutrient Separating Baffle Box (NSBB) After each runoff event initially, then at least quarterly. Local and State regulation may require every 90 days [96] Inspection and maintenance checklist; [97] Vacuum out sediment chambers when sediment accumulation exceeds 50% storage volume [98] Vacuum truck
Manhole Baffle Box Frequently for first two years following installation, then site specific [99] Fully cleaned at least once per year [100] Vacuum truck; One half day; Average cost $450 [101]
Environment 21 StormPro At least quarterly until a more accurate schedule can be determined [102] Maintenance data sheet Sediment should be removed when sediment depth in first chamber is 50% of design sediment storage depth or at least once per year [103] Truck-mounted sewer and catch basin cleaner with vacuum pump [104]
BaySeparator by BaySaver At least every 6 months initially, then site specific [105] Maintenance instructions Cleaning recommended every 12-36 months or when 2 feet of sediment have accumulated [106] Vacuum truck [107]
Sump Manhole with SAFL Baffle 45 minute installation [108] Three times per year for first two years Sediment removed before it reaches the bottom of the SAFL baffle Vacuum truck [109]
Deep sump catch basin Four times per year and at the end of foliage and snow- removal seasons [110] Four times per year or when deposit depth is greater than ½ depth from bottom of invert to lowest pipe [111] Hood required Vacuum truck or clamshell bucket [112]
Forebay/pre-settling basin Hard floor (concrete or grouted stone) allows definition of bottom and ease of maintenance. Provide appropriate stabilized maintenance access for heavier equipment at no more than 2% cross slope and no more than 10% longitudinal slope Monthly [113] Four times per year or when sediment depth is >3 ft. A hard bottom such as concrete facilitates removal, during design ensure forebay is vehicle accessible [114]; [115] Forebay should be designed to withstand 2-yr and 10-yr velocities without scouring [116] Vacuum truck skid-loader, or backhoe

This page was last edited on 13 April 2020, at 17:59.

Template:Footer