(A) It is recognized that developed areas, as compared to undeveloped areas, generally have increased imperviousness, decreased infiltration rates, increased runoff rates, and increased concentrations of pollutants such as fertilizers, herbicides, greases, oil, salts and other pollutants. As new development and re-development continues within the corporate boundaries of the City of Decatur, measures must be taken to intercept and filter pollutants from storm water runoff prior to reaching regional creeks, streams, and rivers. Through the use of appropriate best management practices (BMPs) to treat the water quality volume (WQv) or the water quality flow (Qwq), storm water runoff will be filtered and harmful amounts of sediment, nutrients, and contaminants will be removed.
(B) It is also recognized that another major source of pollution in many Indiana streams, including those within the corporate boundaries of the City of Decatur, is the streambank erosion associated with urbanizing watersheds. Stream channels develop their shape in response to the volume and rate of runoff that they receive from their contributing watersheds. Research has shown that in hydrologically stable watersheds, the stream flow responsible for most of the shaping of the channel (called the bankfull flow) occurs between every one to two years. When land is developed, the volume and rate of runoff from that land increases for these comparatively small flooding events that are not normally addressed by the detention practices and the stream channel will adapt by changing its shape. As the stream channel works to reach a new stable shape, excess erosion occurs. As new development and re-development continues within the corporate boundaries of the City of Decatur, measures must be taken to minimize the impact of such development or re-development on streambank erosion. Through the use of appropriate best management practices (BMPs) to retain and/or detain and slowly release the channel protection volume (CPv), the volume and rate of runoff for channel forming flows will be reduced in an attempt to minimize increased streambank erosion in the receiving streams and channels.
(C) The project site owner must submit to the Department a storm water pollution prevention plan (SWPPP) that shows placement of appropriate BMP(s) from a pre-approved list of BMPs specified in the City of Decatur Storm Water Technical Standards Manual. The SWPPP submittal shall include an operation and maintenance manual for all post-construction BMP(s) included in the project and a notarized maintenance agreement, consistent with the sample agreement provided in the City of Decatur Storm Water Technical Standards Manual, providing for the long-term maintenance of those BMPs, both of which shall be recorded with the deed for the property on which the project is located. The noted BMP(s) must be designed, constructed, and maintained according to guidelines provided or referenced in the City of Decatur Storm Water Technical Standards Manual. Practices other than those specified in the pre-approved list may be utilized. However, the burden of proof, as to whether the performance and ease of maintenance of such practices will be according to guidelines provided in the City of Decatur Storm Water Technical Standards Manual, would be placed with the applicant. Details regarding the procedures and criteria for consideration of acceptance of such BMPs are provided in the City of Decatur Storm Water Technical Standards Manual.
(D) Gasoline outlets and refueling areas must install appropriate practices (as noted under "Hot Spots” provision in the Technical Standards) to reduce lead, copper, zinc, and polyaromatic hydrocarbons in storm water runoff. These requirements will apply to all new facilities and existing facilities that replace their tanks, regardless of the size of the facility.
(E) Discharges from new development and redevelopment sites will not be allowed directly into karst features without pre-treatment.
(Ord. 2023-11, passed 8-1-2023)