7.3 Stormwater

All land development activity must manage construction and post-construction stormwater runoff in accordance with this section.

1. Any land development activity that will involve soil disturbance of one-quarter acre (10,890 square feet) or more, or soil disturbance of less than one- quarter acre that is part of a larger development plan consisting of at least one-quarter acre in area, requires submission by the applicant of a Stormwater Pollution Prevention Plan (SWPPP) prepared per the requirements of the Buffalo Sewer Authority. Applicants proposing land development activity that falls below this threshold must manage construction and post-construction stormwater runoff, but are not required to prepare a SWPPP. A SWPPP must be completed as part of site plan review.
2. The SWPPP must be prepared by a New York State licensed engineer or registered landscape architect, and must be signed and stamped by the professional preparing the plan, who must certify that the design of all stormwater management practices meets the requirements of this section.
3. The property owner must ensure proper operation and maintenance of permanent stormwater management facilities installed in accordance with this section, and must provide certification of their continued performance every five years.

1. The below documents serve as the official guides and specifications for stormwater management. Stormwater management practices that are designed and constructed per the most recent or successor versions of these technical documents are presumed to meet the performance standards of this section.
   1. New York State Stormwater Management Design Manual (New York State Department of Environmental Conservation).
   2. New York State Standards and Specifications for Erosion and Sediment Control (New York State Department of Environmental Conservation).
   3. TR-55 Urban Hydrology for Small Watersheds (United States Department of Agriculture).
   4. Precipitation Frequency Atlas of the United States (National Oceanic and Atmospheric Administration).
2. Where stormwater management practices are not in accordance with technical documents referenced in Section 7.3.2.A, the applicant must demonstrate equivalence to the technical standards.

All land development activity is subject to the following performance and design criteria:

1. For all projects for which a SWPPP is required, erosion and sediment control measures must be undertaken which are in accordance with the New York State Standards and Specifications for Erosion and Sediment Control.

2. Where technically feasible, stormwater discharges must be directed to sewers according to the following hierarchy of preference:

   1. Storm Only Sewer.
   2. Storm Overflow Sewer.
   3. Storm Relief Sewer.
   4. Combined Sewer.

3. Where the stormwater will be released to a storm- only sewer or storm overflow sewer, the project must meet both the sizing criteria and water quality standards contained in the New York State Stormwater Management Design Manual.

4. Where stormwater will be released to a storm relief sewer or combined sewer, the project must demonstrate that post-development peak flows during a 25-year storm will be less than pre- development peak flows during a 2-year storm.

1. Where practicable, stormwater management facilities should utilize Green Infrastructure Best Management Practices (BMPs) according to the following hierarchy of preference:

   1. Conservation of natural areas.
   2. On-site infiltration practices including, but not limited to, bioretention cells/rain gardens, vegetated swales, filter strips, constructed wetlands and porous pavement.
   3. Capture and reuse of runoff through low- impact practices including, but not limited to, green roofs, blue roofs, and rain barrels or cisterns.

2. Where on-site green infrastructure BMPs are not feasible for all or a portion of stormwater runoff volume due to factors including, but not limited to, contamination, high groundwater table, shallow bedrock, or poor infiltration rates, or where it can be proven that such practices would cause property or environmental damage, the remaining portion may be treated by another stormwater management practice acceptable to the Buffalo Sewer Authority.

3. In cases where on-site BMPs have been determined not to be feasible, the Buffalo Sewer Authority may consider the following alternative stormwater management practices to meet water quantity standards, in order of preference:

   1. Off-site green infrastructure BMPs within the same sub-sewershed;
   2. Retention through subsurface infiltration or underground storage vaults;
   3. Detention through underground storage vaults.

4. BMPs that are implemented within the public right-of-way may not be designed to accept or treat stormwater from private property, except for sewer system infrastructure per the specifications of the Buffalo Sewer Authority.

5. Where underground storage vaults are utilized for detention discharge to a storm only or storm overflow sewer, water quality standards must be met through the use of a New York State Department of Environmental Conservation approved proprietary technology.

6. Where stormwater management performance standards cannot be met due to unique site constraints or any other conditions beyond the control of the applicant, the Buffalo Sewer Authority may provide an exemption to the standards of this section.