PROJECT SHEET CONSTRAINED SITE STANDARD

Complete one Project Sheet for each project that is Constrained and includes Stormwater Quality BMPs.

CONSTRAINED REDEVELOPMENT SITES

Constrained Redevelopment Sites are sites where the existing condition is >35% imperviousness and the proposed redevelopment will result in >75% imperviousness. If the proposed redevelopment will result  in>75% imperviousness, but the existing condition is <35% imperviousness, the Constrained Site  Standard cannot be used and Base Design Standards must be followed. The Constrained Site Standard can only be used if it is determined that it is not practicable to meet any of the Base Design Standards. It is incumbent on the design engineer to demonstrate adherence to Base Design Standards has been thoroughly evaluated and found to be infeasible before a Constrained Site Standard is proposed.

SITE INFORMATION

DESIGN STANDARDS

Design Standards may be used in combination, as necessary, to meet the requirements. Additional design methods may be considered if they comply with the MS4 Permit. Evaluation of suitability of Stormwater Quality Control Measures (BMPs) is based on pollutant removal, flood attenuation and long-term   maintenance. BMPs must be designed in accordance with the most current version of USDCM vol. 3, Chapter 4

 “Treatment BMPs” and meet the specific requirements for each Design Standard used.

1. Indicate below, which Design Standards will be used for the project, and
2. Complete a separate, corresponding Design Standards checklist for each BMP (e.g., WQCV, etc.)

CHECKLIST Constrained WQCV Standard

APPLICABILITY

Constrained Redevelopment Sites are sites where the existing condition is >35% imperviousness and the proposed redevelopment will result in >75% imperviousness. If the proposed redevelopment will result  in >75% imperviousness, but the existing condition is <35% imperviousness, the Constrained Site  Standard cannot be used and Base Design Standards must be followed. The Constrained Site Standard can only be used if it is determined that it is not practicable to meet any of the Base Design Standards. It is incumbent on the design engineer to demonstrate adherence to Base Design Standards has been thoroughly evaluated and found to be infeasible before a Constrained Site Standard is proposed.

The minimum treatment levels are included below, and treatment should be maximized to the extent feasible under constrained site conditions.

CONSTRAINED WQCV STANDARD Criteria

Control measure(s) must be designed to provide, at a minimum, treatment and/or infiltration of the WQCV for 50% of the site.

Complete checklist if using the Constrained WQCV Standard to meet Design Standard requirements.

CHECKLIST Constrained Pollutant Removal Standard

APPLICABILITY

Constrained Redevelopment Sites are sites where the existing condition is >35% imperviousness and the proposed redevelopment will result in >75% imperviousness. If the proposed redevelopment will result in >75% imperviousness, but the existing condition is <35% imperviousness, the Constrained Site Standard cannot be used, and Base Design Standards must be followed. The Constrained Site Standard can only be used if it is determined that it is not practicable to meet any of the Base Design Standards. It is incumbent on the design engineer to demonstrate adherence to Base Design Standards has been thoroughly evaluated and found to be infeasible before a Constrained Site Standard is proposed.

The minimum treatment levels are included below, and treatment should be maximized to the extent feasible under constrained site conditions.

CONSTRAINED POLLUTANT REMOVAL STANDARD Criteria

Control measure(s) must be designed to provide treatment of the 80th percentile storm event. The control measure(s) shall be designed to treat stormwater runoff in a manner expected to reduce the even mean concentration of total suspended solids (TSS), at a minimum, to a median value of 30mg/L or  less for 50% of the site. Substantiating data must meet criteria in USDCM vol.3, T-11 and be included in  the submittal.

Complete checklist if using the Constrained Pollutant Removal Standard to meet Design Standard requirements.

CHECKLIST Constrained Runoff Reduction Standard

APPLICABILITY

Constrained Redevelopment Sites are sites where the existing condition is >35% imperviousness and the proposed redevelopment will result in >75% imperviousness. If the proposed redevelopment will result in >75% imperviousness, but the existing condition is <35% imperviousness, the Constrained Site Standard cannot be used, and Base Design Standards must be followed. The Constrained Site Standard can only be used if it is determined that it is not practicable to meet any of the Base Design Standards. It is incumbent on the design engineer to demonstrate adherence to Base Design Standards has been thoroughly evaluated and found to be infeasible before a Constrained Site Standard is proposed.

The minimum treatment levels are included below, and treatment should be maximized to the extent feasible under constrained site conditions.

CONSTRAINED RUNOFF REDUCTION STANDARD Criteria

Control measure(s) must be designed to infiltrate, evaporate or evapotranspire, at a minimum, a quantity of water equal to 30% of what the calculated WQCV would be if all impervious area discharged without infiltration. This Standard can be met through practices such as Green Infrastructure and Low Impact Development practices.

Complete checklist if using the Constrained Runoff Reduction Standard to meet Design Standard requirements.