7 units per acre) C.Vertical Density, (Floor to Area Ratio (FAR) of 2 or > 18 units per acre) D.Mixed use and Transit Oriented Development (within ½ mile of transit) NO Will rates and volume of stormwater runoff from each site where construction activity is described as A-D, meet 50% of pre-development rates and volume of stormwater runoff. YES NO YES NO MCM 5 Limitations Any construction activity resulting in any of the following, is not authorized to use infiltration BMPs, on-site, to meet the terms and condition of MCM5. NPDES permitted industrial activity prohibited from infiltration, Stormwater discharges from vehicle fuieling and maint. Areas, Discharges from areas 1000ft up-gradient, or 100ft down-gradient of karst features, Discharges from areas with less than 3ft separation distance from bottom of infiltration system to elevation of seasonal high groundwater or top of bedrock, Areas from etc etc etc. YES NO Off-site mitigation of stormwater must occur within the timeframe specified in the MS4s regulatory mechanism. The off-site mitigation must result in one of the following outcomes. 1.Within the stormshed, a 1:1 decrease in stormwater discharge rates and volumes equivalent to the pre- development hydrology of the site of the construction activity, or 2.Within the watershed, a 2:1 decrease in stormwater discharge rates and volumes equivalent to the pre- development hydrology of the site of the construction activity, or 3.Within the MS4, a 3:1 decrease in stormwater discharge rates and volumes equivalent to the pre-development hydrology of the site of the construction activity. Will any of these outcomes be achieved? Off-site mitigation of stormwater must occur within the timeframe specified in the MS4s regulatory mechanism. The off-site mitigation must result in one of the following outcomes. 1.Within the stormshed, a 1:1 decrease in stormwater discharge rates and volumes that are a minimum of 50% less than the pre- development hydrology of the site of the construction activity, or 2.Within the watershed, a 2:1 decrease in stormwater discharge rates and volumes that are a minimum of 50% less than the pre- development hydrology of the site of the construction activity, or 3.Within the MS4, a 3:1 decrease in stormwater discharge rates and volumes that are a minimum of 50% less than the pre- development hydrology of the site of the construction activity. Will any of these outcomes be achieved? YES The regulatory mechanism developed, implemented and enforced by the MS4 will not allow the construction activity to take place.">

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Post-construction rates and volume of stormwater runoff on-site will be equal to or less than that of pre-development rates and volume of stormwater runoff?

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Presentation on theme: "Post-construction rates and volume of stormwater runoff on-site will be equal to or less than that of pre-development rates and volume of stormwater runoff?"— Presentation transcript:

1 Post-construction rates and volume of stormwater runoff on-site will be equal to or less than that of pre-development rates and volume of stormwater runoff? Post-construction stormwater management is in compliance with MCM5 and Anti-deg standards. No further action required. mitigation must be conductede that results in rates and volumes of runoff equal to the projects pre- development hydrology within 1) the stormshed, 2) watershed, 3) the MS4 YES NO MCM 5 – All Construction (DRAFT #1) NO Post const. rates and volume are equal to or less than that of pre-const (existing land use). YES Can mitigation be conducted up-stream and prior to the initiation of the const. project. MCM5 Anti-deg YES NO Incentives for defined re- developed sites (e.g. ???). Must meet a minimum 50%? of pre-developmennt rates and volumes of runoff. Permittee must conduct a Social and Economic Justification. This will involve the proposal of the least degrading alternative. Anit-deg is satisfied. Sites where infiltration should not occur. What standards should they meet? exclusions

2 MCM 5 – Post-Construction Runoff Control (DRAFT #2) YES NO YES Post-construction stormwater management for that construction activity is in compliance with MCM5 and Anti-deg standards. No further action required. Rates and volume of stormwater runoff from each site where construction activity takes place will be equal to or less than pre-development rates and volume of stormwater runoff. Will the construction activity be conducted on land that is described as any of the following? A.A brownfield site B. High Density (> 7 units per acre) C.Vertical Density, (Floor to Area Ratio (FAR) of 2 or > 18 units per acre) D.Mixed use and Transit Oriented Development (within ½ mile of transit) Will rates and volume of stormwater runoff from each site where construction activity is described as A-D, meet 50% of pre- development rates and volume of stormwater runoff. Post const. rates and volume are equal to or less than that of pre-const (existing land use). Mitigation must be conducted that results in rates and volumes of runoff equal to the projects pre-development hydrology within 1) the stormshed, 2) watershed, 3) the MS4 Can mitigation be conducted up-stream and prior to the initiation of the const. project. Anit-deg is satisfied Permittee must conduct a Social and Economic Justification. This will involve the proposal of the least degrading alternative. YES NO Mitigation must be conducted that results in rates and volumes of runoff being at least 50% of the project’s pre- development hydrology within 1) the stormshed, 2) watershed, 3) the MS4 MCM 5 Limitations Any construction activity resulting in any of the following, is not authorized to use infiltration BMPs to meet the terms and condition of MCM5. NPDES permitted industrial activity prohibited from infiltration, Stormwater discharges from vehicle fuieling and maint. Areas, Discharges from areas 1000ft up-gradient, or 100ft down- gradient of karst features, Discharges from areas with less than 3ft separation distance from bottom of infiltration system to elevation of seasonal high groundwater or top of bedrock, Areas from etc etc etc. "Construction Activity" includes construction activity as defined in 40 C.F.R. pt. 122.26(b)(14)(x) and small construction activity as defined in 40 C.F.R. pt. 122.26(b)(15). This includes a disturbance to the land that results in a change in the topography, existing soil cover (both vegetative and non-vegetative), or the existing soil topography that may result in accelerated stormwater runoff, leading to soil erosion and movement of sediment into surface waters or drainage systems. Examples of construction activity may include clearing, grading, filling, and excavating. Construction activity includes the disturbance of less than one acre of total land area that is a part of a larger common plan of development or sale if the larger common plan will ultimately disturb one (1) acre or more. “Pre-Development” means stormwater run-off rates and volume calculated using native soils and vegetation. “Pre-Construction” means land use prior to the beginning of a specific construction activity. “Post-Construction” means land use immediately following a specific construction activity. Draft Definitions Box 1 Box 3 Box 2 Box 4 Box 8 Box 5 Box 6 Box 10 Box 9 Box 7 Box 11 Box 14 Box 13 Box 15 Box 12 YES

3 "Construction Activity" includes construction activity as defined in 40 C.F.R. pt. 122.26(b)(14)(x) and small construction activity as defined in 40 C.F.R. pt. 122.26(b)(15). This includes a disturbance to the land that results in a change in the topography, existing soil cover (both vegetative and non-vegetative), or the existing soil topography that may result in accelerated stormwater runoff, leading to soil erosion and movement of sediment into surface waters or drainage systems. Examples of construction activity may include clearing, grading, filling, and excavating. Construction activity includes the disturbance of less than one acre of total land area that is a part of a larger common plan of development or sale if the larger common plan will ultimately disturb one (1) acre or more. “Pre-Development” means stormwater run-off rates and volume calculated using native soils and vegetation. “Pre-Construction” means land use prior to the beginning of a specific construction activity. “Post-Construction” means land use immediately following a specific construction activity. Draft Definitions MCM 5 – Post-Construction Runoff Control (DRAFT #3) Rates and volume of stormwater runoff from each site where construction activity takes place will be equal to or less than pre-development rates and volume of stormwater runoff. YES Post-construction stormwater management for that construction activity is in compliance with MCM5. No further action required. Will the construction activity be conducted on land that is described as any of the following? A.A brownfield site B. High Density (> 7 units per acre) C.Vertical Density, (Floor to Area Ratio (FAR) of 2 or > 18 units per acre) D.Mixed use and Transit Oriented Development (within ½ mile of transit) NO Will rates and volume of stormwater runoff from each site where construction activity is described as A-D, meet 50% of pre-development rates and volume of stormwater runoff. YES NO YES NO MCM 5 Limitations Any construction activity resulting in any of the following, is not authorized to use infiltration BMPs, on-site, to meet the terms and condition of MCM5. NPDES permitted industrial activity prohibited from infiltration, Stormwater discharges from vehicle fuieling and maint. Areas, Discharges from areas 1000ft up-gradient, or 100ft down-gradient of karst features, Discharges from areas with less than 3ft separation distance from bottom of infiltration system to elevation of seasonal high groundwater or top of bedrock, Areas from etc etc etc. YES NO Off-site mitigation of stormwater must occur within the timeframe specified in the MS4s regulatory mechanism. The off-site mitigation must result in one of the following outcomes. 1.Within the stormshed, a 1:1 decrease in stormwater discharge rates and volumes equivalent to the pre- development hydrology of the site of the construction activity, or 2.Within the watershed, a 2:1 decrease in stormwater discharge rates and volumes equivalent to the pre- development hydrology of the site of the construction activity, or 3.Within the MS4, a 3:1 decrease in stormwater discharge rates and volumes equivalent to the pre-development hydrology of the site of the construction activity. Will any of these outcomes be achieved? Off-site mitigation of stormwater must occur within the timeframe specified in the MS4s regulatory mechanism. The off-site mitigation must result in one of the following outcomes. 1.Within the stormshed, a 1:1 decrease in stormwater discharge rates and volumes that are a minimum of 50% less than the pre- development hydrology of the site of the construction activity, or 2.Within the watershed, a 2:1 decrease in stormwater discharge rates and volumes that are a minimum of 50% less than the pre- development hydrology of the site of the construction activity, or 3.Within the MS4, a 3:1 decrease in stormwater discharge rates and volumes that are a minimum of 50% less than the pre- development hydrology of the site of the construction activity. Will any of these outcomes be achieved? YES The regulatory mechanism developed, implemented and enforced by the MS4 will not allow the construction activity to take place.

4 "Construction Activity" includes construction activity as defined in 40 C.F.R. pt. 122.26(b)(14)(x) and small construction activity as defined in 40 C.F.R. pt. 122.26(b)(15). This includes a disturbance to the land that results in a change in the topography, existing soil cover (both vegetative and non-vegetative), or the existing soil topography that may result in accelerated stormwater runoff, leading to soil erosion and movement of sediment into surface waters or drainage systems. Examples of construction activity may include clearing, grading, filling, and excavating. Construction activity includes the disturbance of less than one acre of total land area that is a part of a larger common plan of development or sale if the larger common plan will ultimately disturb one (1) acre or more. “Pre-Development” means stormwater run-off rates and volume calculated using native soils and vegetation. “Pre-Construction” means land use prior to the beginning of a specific construction activity. “Post-Construction” means land use immediately following a specific construction activity. Draft Definitions Anti-Degradation (DRAFT #3) YES NO YES For any given construction activity within the jurisdiction of the MS4 Post-construction rates and volume of stormwater runoff are equal to or less than that of pre-construction rates and volume of stormwater runoff at the construction site. Anti-Degradation is satisfied. No further action regarding Anti-Deg required. NO Does the construction activity in question have a direct or indirect overland discharge that flows to, and that originates with within one mile of, a prohibited ORVW? YES The regulatory mechanism developed, implemented and enforced by the MS4 will not allow the construction activity to take place. NO Permittee must ensure a Social and Economic Justification (i.e. a justification why the lowering of water quality of the receiving water is necessary and important), and proposal of the least degrading alternative, is submitted to the Agency for approval or disapproval. Social and Economic Justification is approved by the Agency? Off-site mitigation of stormwater must occur within the timeframe specified in the MS4s regulatory mechanism. The off-site mitigation must be conducted up-stream of, and prior to the proposed construction activity, and must result in one of the following outcomes. 1.Within the stormshed, a 1:1 decrease in stormwater discharge rates and volumes equivalent to the pre- development hydrology of the site of the construction activity, or 2.Within the watershed, a 2:1 decrease in stormwater discharge rates and volumes equivalent to the pre- development hydrology of the site of the construction activity, or 3.Within the MS4, a 3:1 decrease in stormwater discharge rates and volumes equivalent to the pre-development hydrology of the site of the construction activity. Can this be achieved for the construction activity in question? YES NO We need to wordsmith #’s 1, 2 and 3. Hope you get the point.


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