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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.
2
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.
2
| 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 | - |
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.
51
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.
51
| 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 | - |
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.
16
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.
16
| 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 | - |
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
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 | - |
Dry Basin (using CASQA Drawdown)
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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.
1
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.
1
| Material Accumulation | 35% | - | - | - |
| 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 - CASQA Drawdown Method | 50% | 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.
49
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.
49
| 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.
10
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.
10
| 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.
23
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.
23
| 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 - CASQA Drawdown Method | 80% | 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.
69
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.
69
| 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.
39
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.
39
| 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 | - |
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.
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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.
194
| 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 | - |
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
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 | - |
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.
515
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.
515
| Sediment Trap Capacity | 100% | - | 1 ft | - |
| Conveyance - Inlet Condition | pass/fail | n/a | n/a | - |
| Conveyance - Outlet Condition | pass/fail | n/a | n/a | - |
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.
9
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.
9
| Material Accumulation | 100% | - | - | - |
| Conveyance - Inlet Condition | pass/fail | n/a | n/a | - |
| Conveyance - Outlet Condition | pass/fail | n/a | n/a | - |
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.
20
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.
20
| 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 | - |
Underground Infiltration Gallery
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Centralized facility or aggregation of facilities to which concentrated runoff is conveyed; consisting of a diversion/bypass, an inlet sediment trap, an infiltration chamber of underground perforated pipe in a drain rock filled sump, and terminal sediment trap.
9
Centralized facility or aggregation of facilities to which concentrated runoff is conveyed; consisting of a diversion/bypass, an inlet sediment trap, an infiltration chamber of underground perforated pipe in a drain rock filled sump, and terminal sediment trap.
9
| Material Accumulation using Stadia Rod | 35% | - | - | - |
| Conveyance - Inlet Condition | pass/fail | n/a | n/a | - |
| Conveyance - Outlet Condition | pass/fail | n/a | n/a | - |
| Infiltration - CASQA Drawdown Method | 65% | n/a | n/a | - |
Underground Perf Pipe, Sediment Can and Swale
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A series of distributed inline trenches that contain underground perforated pipe in a matrix of drain rock that captures and treats stormwater flow from adjacent roadways.
7
A series of distributed inline trenches that contain underground perforated pipe in a matrix of drain rock that captures and treats stormwater flow from adjacent roadways.
7
| Material Accumulation using Stadia Rod | 35% | - | - | - |
| Wetland and Upland Species Vegetative Cover | 15% | 0% | 10% | - |
| Conveyance - Inlet Condition | pass/fail | n/a | n/a | - |
| Conveyance - Outlet Condition | pass/fail | n/a | n/a | - |
| Infiltration - CASQA Drawdown Method | 50% | n/a | n/a | Runoff as Pass/Fail |
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.
32
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.
32
| 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 | - |