A list of the various Treatment BMP Types is provided here. To see individual BMPs, visit the Treatment BMP page.

Bed Filter (using CHP)
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A flow-through structure that uses granular media (e.g. sand or activated alumina) to actively filter stormwater to remove stormwater pollutants. Filtration is controlled by the flow rate through the media and discharge via an underdrain or outlet. Little to no volume loss occurs. May be confined space but not always. Pollutant load reductions achieved by reduced concentrations in effluent. No stormwater volume reduction occurs. Typically, moderate sized centralized BMPs but can be small decentralized BMPs treating small areas of imperviousness.
0
Infiltration Rate - Constant Head Permeameter (CHP) 100% - 20 % decline from benchmark Infiltration Rate - Calculated Off-System
Conveyance - Inlet Condition pass/fail n/a n/a -
Conveyance - Outlet Condition pass/fail n/a n/a -
Do Not Use - Bed Filter
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A flow-through structure that uses granular media (e.g. sand or activated alumina) to actively filter stormwater to remove stormwater pollutants. Filtration is controlled by the flow rate through the media and discharge via an underdrain or outlet. Little to no volume loss occurs. May be confined space but not always. Pollutant load reductions achieved by reduced concentrations in effluent. No stormwater volume reduction occurs. Typically, moderate sized centralized BMPs but can be small decentralized BMPs treating small areas of imperviousness.
0
Infiltration Rate - User Defined Method 100% - 20 % decline from benchmark -
Conveyance - Inlet Condition pass/fail n/a n/a -
Conveyance - Outlet Condition pass/fail n/a n/a -
Do Not Use - Biofilter
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Vegetated BMP where stormwater is filtered through a specialized soil media and discharged via an underdrain. BMP may or may not be lined but little to no exfiltration of volumes. Outlet design requires surface ponding prior to surface outflow typically with a maximum ponding depth of 6 inches. Site designed biofiltration systems use specialized soil media ideally 18-24 inches in depth to enhance biogeochemical processes to retain and transform pollutants. Proprietary biofilter designs vary and specialized soil media may or may not be accessible for inspection. Small to moderate sized decentralized BMP accepting runoff from a single land use drainage area.
0
Runoff 40% 0 s 120 s -
Wetland and Grass Vegetative Cover 60% 100% 80% -
Conveyance - Inlet Condition pass/fail n/a n/a -
Conveyance - Outlet Condition pass/fail n/a n/a -
Do Not Use - Cartridge Filter
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Cartridge filters are contained within a confined space similar to treatment vaults. Granular or media filter to remove fraction of stormwater pollutants. The proprietary filter media type should be specifically selected to target removal of the pollutants of concern, resulting in down-gradient stormwater concentration reductions. No volume loss occurs due to impervious base. Treatment BMP strategically placed in stormwater drainage path and treated water is conveyed downgradient. Typically a moderate sized Treatment BMP type constructed in Lake Tahoe.
0
Vault Capacity 100% - 50 % decline from benchmark -
Conveyance - Inlet Condition pass/fail n/a n/a -
Conveyance - Outlet Condition pass/fail n/a n/a -
Installation pass/fail n/a n/a -
Standing Water - Initial Observation pass/fail n/a n/a -
Standing Water - Second Observation pass/fail n/a n/a -
Do Not Use - Drop Inlet
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Stormwater feature placed strictly to collect and convey stormwater. A drop inlet that includes a sump to capture particulate pollutants is termed a Catch Basin. Typically conveying water from a roadway, parking lot or other impervious surface to a culvert or storm drain and provides no water quality benefit downgradient.
0
Conveyance - Inlet Condition pass/fail n/a n/a -
Conveyance - Outlet Condition pass/fail n/a n/a -
Do Not Use - Dry Basin
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A flow through basin with discrete inlets and outlets designed to detain stormwater runoff for some minimum time to reduce peak flows. Design treatment capacity and draw down time will vary across specific BMPs. One or more outflow offices may exist but there is at least one at base of basin to allow complete draining between storms. Increased draw down times can increase particle capture via settling within the basin. Footprint is pervious and infiltration capacity of base maintained to consistently infiltrate some fraction of volumes detained to unsaturated zone. Wetland and riparian vegetation species distribution is minimal to absent. Moderate distribution of grass and/or tree species likely and acceptable. Moderate to large sized centralized BMPs that accept runoff from mixed land use drainage areas.
0
Material Accumulation 35% - - -
Infiltration Rate - User Defined Method 50% - 20 % decline from benchmark -
Wetland Vegetative Cover 15% 0% 20% -
Conveyance - Inlet Condition pass/fail n/a n/a -
Conveyance - Outlet Condition pass/fail n/a n/a -
Do Not Use - Infiltration Basin
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A flow through BMP with highly permeable substrate (aggregate or rock) designed to store and infiltrate significant volumes of stormwater into unsaturated zone. Little to no surface detainment storage. Vegetation distribution should be minimal and preferably absent. Moderate to large sized centralized BMP, accepting runoff from a mixed land use drainage area.
0
Infiltration Rate - User Defined Method 80% - 20 % decline from benchmark -
Wetland Vegetative Cover 20% 0% 20% -
Conveyance - Inlet Condition pass/fail n/a n/a -
Conveyance - Outlet Condition pass/fail n/a n/a -
Do Not Use - Infiltration Feature
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A small scale structure designed to retain stormwater from small impervious drainage area and infiltrate into unsaturated zone. Land surface modified to sustain maximum infiltration rates, typically consisting of vertical excavation of native soils and filling with coarse drain rock or other highly permeable material. Vegetation is absent. Typically, a small sized decentralized BMP, accepting runoff from a single land use drainage area.
0
Runoff 75% 0 s 120 s -
Wetland and Upland Species Vegetative Cover 25% 0% 10% -
Conveyance - Inlet Condition pass/fail n/a n/a -
Conveyance - Outlet Condition pass/fail n/a n/a -
Do Not Use - Porous Pavement
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Use of sustainable materials to create a durable, pervious surface overlaying a crushed stone base that allow stormwater to percolate and infiltrate into the underlying soil. Porous pavement can include an underlying reservoir to increase infiltration rates. Local stormwater is typically not routed to a porous pavement surface, but rather constructed to minimize the volume of stormwater generated and routed downgradient from a previously impervious surface. Footprint of structural BMP type can vary greatly, typically used for parking lots, sidewalks, driveways or other impervious surfaces.
0
Infiltration Rate - User Defined Method 100% - 20 % decline from benchmark -
Conveyance - Inlet Condition pass/fail n/a n/a -
Conveyance - Outlet Condition pass/fail n/a n/a -
Do Not Use - Sediment Trap
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Typically constructed on site using low cost vertical corrugated metal (CMP) and trash rack placed in stormwater flow path to capture sediment, debris, coarse particles and associated pollutants in a deep (>5ft) sump. Minimal to no volume loss occurs due to vertical accumulation of road side particulates and relatively small footprint. Typically located on road shoulder stormwater flow paths. Small sized Treatment BMP type constructed in Lake Tahoe.
0
Sediment Trap Capacity 100% - 1 ft -
Conveyance - Inlet Condition pass/fail n/a n/a -
Conveyance - Outlet Condition pass/fail n/a n/a -
Do Not Use - Settling Basin
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Open flow through structures used to detain stormwater volumes and settle particulate pollutants prior to outflow. Pollutant load reductions are realized by concentration reductions with no volume reduction via infiltration due to impervious or highly impermeable base. Size and application of settling basins can vary. Setting basins are common at the inlet of another structural BMPs to pre-treat inflowing stormwater prior to stormwater entering subsequent structural BMP. If inventory and assessment of the settling basin is desired independent from the next structural BMP in the treatment train, there are two options: Large scale Settling Basin draining a mixed land use area can be classified and assessed as a Treatment Vault. Smaller sized Settling Basins draining a single land use area can be classified and assessed as a Catch Basin.
0
Material Accumulation 100% - - -
Conveyance - Inlet Condition pass/fail n/a n/a -
Conveyance - Outlet Condition pass/fail n/a n/a -
Do Not Use - Treatment Vault
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A subsurface flow-through structure that physically separates sediment, trash, leaf litter, debris and other particulate pollutants from stormwater via various water separation or settling techniques. Pollutant load reductions are realized by concentration reductions. No volume reduction occurs due to impervious base. Many manufactured and proprietary models are available that employ various physical techniques to separate and capture debris and particulate. Accumulation of material at base of BMP can be observed and measured via manhole access. Moderate sized centralized structure accepting runoff from either a large single or mixed land use drainage area.
0
Vault Capacity 100% - 50 % decline from benchmark -
Conveyance - Inlet Condition pass/fail n/a n/a -
Conveyance - Outlet Condition pass/fail n/a n/a -
Do Not Use - Wet Basin
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A flow through basin with discrete inlets and outlets designed to retain some volume stormwater runoff in a persistent pool of surface water. Designs may include additional detainment storage of stormwater for some minimum time to reduce peak flows. Wet pool capacity, treatment capacity and draw down time of treated volumes will vary across specific BMPs. One or more outflow offices may exist at different elevations. Lowest outlet elevation sets wet pool capacity. Dense vegetation is common. Dominant vegetation is wetland species and can be supplemented with riparian species with very high densities. Substrate is typically fine organic matter and silt, making volume reductions via infiltration negligible. Volume reductions occur primarily by evapotranspiration. Moderate to large sized centralized BMPs that accept runoff from mixed land use drainage areas.
1
Material Accumulation 60% - - -
Wetland and Riparian Vegetative Cover 40% 57.5% +/- 17.5 % of benchmark (47.4375 - 67.5625 %) -
Conveyance - Inlet Condition pass/fail n/a n/a -
Conveyance - Outlet Condition pass/fail n/a n/a -
Dry Basin (using CHP)
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A flow through basin with discrete inlets and outlets designed to detain stormwater runoff for some minimum time to reduce peak flows. Design treatment capacity and draw down time will vary across specific BMPs. One or more outflow offices may exist but there is at least one at base of basin to allow complete draining between storms. Increased draw down times can increase particle capture via settling within the basin. Footprint is pervious and infiltration capacity of base maintained to consistently infiltrate some fraction of volumes detained to unsaturated zone. Wetland and riparian vegetation species distribution is minimal to absent. Moderate distribution of grass and/or tree species likely and acceptable. Moderate to large sized centralized BMPs that accept runoff from mixed land use drainage areas.
0
Material Accumulation 35% - - -
Infiltration Rate - Constant Head Permeameter (CHP) 50% - 20 % decline from benchmark Infiltration Rate - Calculated Off-System
Wetland Vegetative Cover 15% 0% 20% -
Conveyance - Inlet Condition pass/fail n/a n/a -
Conveyance - Outlet Condition pass/fail n/a n/a -
Dry Basin (using User Defined Infiltration Rate Method)
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A flow through basin with discrete inlets and outlets designed to detain stormwater runoff for some minimum time to reduce peak flows. Design treatment capacity and draw down time will vary across specific BMPs. One or more outflow offices may exist but there is at least one at base of basin to allow complete draining between storms. Increased draw down times can increase particle capture via settling within the basin. Footprint is pervious and infiltration capacity of base maintained to consistently infiltrate some fraction of volumes detained to unsaturated zone. Wetland and riparian vegetation species distribution is minimal to absent. Moderate distribution of grass and/or tree species likely and acceptable. Moderate to large sized centralized BMPs that accept runoff from mixed land use drainage areas.
0
Material Accumulation 35% - - -
Infiltration Rate - User Defined Method 50% - 20 % decline from benchmark Infiltration Rate - Calculated Off-System
Wetland Vegetative Cover 15% 0% 20% -
Conveyance - Inlet Condition pass/fail n/a n/a -
Conveyance - Outlet Condition pass/fail n/a n/a -
Infiltration Basin (using CASQA Drawdown)
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A flow through BMP with highly permeable substrate (aggregate or rock) designed to store and infiltrate significant volumes of stormwater into unsaturated zone. Little to no surface detainment storage. Vegetation distribution should be minimal and preferably absent. Moderate to large sized centralized BMP, accepting runoff from a mixed land use drainage area.
0
Infiltration Rate - CASQA Drawdown Method 80% - 20 % decline from benchmark -
Wetland Vegetative Cover 20% 0% 20% -
Conveyance - Inlet Condition pass/fail n/a n/a -
Conveyance - Outlet Condition pass/fail n/a n/a -
Infiltration Basin (using CHP)
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A flow through BMP with highly permeable substrate (aggregate or rock) designed to store and infiltrate significant volumes of stormwater into unsaturated zone. Little to no surface detainment storage. Vegetation distribution should be minimal and preferably absent. Moderate to large sized centralized BMP, accepting runoff from a mixed land use drainage area.
0
Infiltration Rate - Constant Head Permeameter (CHP) 80% - 20 % decline from benchmark Infiltration Rate - Calculated Off-System
Wetland Vegetative Cover 20% 0% 20% -
Conveyance - Inlet Condition pass/fail n/a n/a -
Conveyance - Outlet Condition pass/fail n/a n/a -
Infiltration Basin (using User Defined Infiltration Rate Method)
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A flow through BMP with highly permeable substrate (aggregate or rock) designed to store and infiltrate significant volumes of stormwater into unsaturated zone. Little to no surface detainment storage. Vegetation distribution should be minimal and preferably absent. Moderate to large sized centralized BMP, accepting runoff from a mixed land use drainage area.
0
Infiltration Rate - User Defined Method 80% - 20 % decline from benchmark Infiltration Rate - Calculated Off-System
Wetland Vegetative Cover 20% 0% 20% -
Conveyance - Inlet Condition pass/fail n/a n/a -
Conveyance - Outlet Condition pass/fail n/a n/a -