(A) A preliminary subdivision plat or site plan (except for minor site plans as defined by this chapter) for a commercial or residential subdivision shall include a stormwater management statement, submitted as part of the required conceptual plan.
(B) A stormwater management statement shall include the following:
(1) Development name and location;
(2) Developer/owner and consultant contact information;
(3) Site description including the following:
(a) Vicinity map;
(b) USGS Topographic Map and the county’s Soil Survey indicating area of development; and
(c) Description of all water courses, impoundments, and wetlands on or adjacent to the site or into which stormwater directly flows.
(4) Statement noting whether the site is located within the conservation zoning or a watershed district;
(5) Impervious area calculations;
(6) A description of the proposed stormwater management system including:
(a) Best Management Practices (BMPs) and preliminary sizes and locations, including post development drainage map delineating the flows diverted to each BMP;
(b) Description and concept for diversion of off-site stormwater; and
(c) Pre-development and post-development discharges for the 10-year and 25-year storms. If the increase in the pre-development discharge is less than 10%, then an additional may not be required unless deemed necessary by the DRB.
(7) Downstream analysis, if required:
(a) Provide topography with the following identified:
1. Drainage areas for the development;
2. Drainage areas for downstream drainage structures; and/or
3. Provide photographs of downstream structures.
(b) For existing streams and ditches, the analysis should focus on increases in velocity and flooding within the stream;
(c) For existing culverts, the analysis should focus on increases in headwater and flooding at the structure;
(d) Identify the point at which the drainage area of the development or redevelopment becomes less than 10% of the total watershed;
(e) All negative impacts of existing improvements and developments shall be identified, if there are no negative impacts, the analysis specifically state and demonstrate that there are not adverse impacts in the increase in site runoff; and
(f) If downstream measures are found to be inadequate, detention or other improvements will be required to minimize downstream impacts.
(Ord. passed 10-17-2011)