(A) The city reserves the right to develop or adopt other guidance documents to serve as design and implementation standards. Other guidance documents distributed by the city should be reviewed and considered when preparing the post-construction SWPPP. These documents may be applied as standards by which designs are to be prepared and controls implemented.
(B) The city shall have authority to implement this subchapter by appropriate regulations, guidance or other related materials. In this regard, technical, administrative or procedural matters may be modified as needed to meet the objectives defined herein, so long as the modifications as to technical, administrative or procedural matters are not contrary or beyond the intent of the objectives defined above.
(1) Regulations, guidance or other related materials that may be given authority by this subchapter may include, but are not limited to: best management practice (BMP) manuals, design regulations and requirements, submittal checklists, review checklists, inspection checklists, certifications, stormwater management manuals and operation and maintenance manuals.
(2) Materials may include information deemed appropriate by the city including guidance and specifications for the preparation of grading plans, selecting environmentally sound practices for managing stormwater, minimum specifications and requirements, more complete definitions and performance standards.
(3) The above referenced documents may restrict or prevent the use of specific products, techniques or management practices (that are to be accepted by the public or are deemed to have a negative impact on public infrastructure or the MS4) that have been identified as unacceptable for performance, maintenance or other technically based reasons.
(4) Documents referenced above may be updated periodically to reflect the most current and effective practices and shall be made available to the public. However, the failure to update the manual shall not relieve any applicant from the obligation to comply with this subchapter, and shall not prevent the city from imposing the most current and effective practices.
(C) The post-construction SWPPP shall include provisions for stormwater quality BMPs functioning independently or in combination. Acceptable stormwater quality BMPs shall be defined by policy and guidance documents as approved by the Stormwater Board.
(D) The post-construction SWPPP shall include provisions for stormwater quality BMPs that are designed to achieve the following design/performance objectives:
(1) Reduce total suspended solids (TSS) from the first flush as defined by land use characteristics and contributing area; or, capture and treatment of at least 0.5-inch precipitation applied over the contributing area;
(2) Reduce or buffer increases in stormwater runoff temperature caused by contact with impervious surfaces;
(3) Reduce or buffer increases in stormwater runoff volume and flow rate caused by increases in directly connected impervious area and overall impervious area; and
(4) Storm water detention/retention facilities shall be designed to address the rate at which flow is released over the entire runoff discharge period and the volume of discharge over the critical design-storm period if defined by city stormwater master plans. The outlet structure shall be designed as a v-notch weir or other multiple stage configurations capable of controlling the discharge rates for the first flush, two-, ten- and 25-year design-storm events. The outlet structure shall be designed to safely bypass the 100-year storm event.
(E) Soil bioengineering, "green" and other "soft" slope and stream bank stabilization methods shall receive preference over rip rap, concrete and other hard armoring techniques. "Hard" alternatives shall only be permitted when their necessity can be demonstrated given site-specific conditions.
(F) Retention-supportive data must be submitted to justify the type of facility selected. If the facility is designed to retain (volume control) all or a significant portion of runoff (as opposed to temporarily detain), then appropriate soils analyses findings shall be submitted to the city. This submission shall also discuss the impacts the facility will have on local karst topography as found through a geotechnical investigation of the site. The facility may be designed to infiltrate runoff to groundwater rather than transmit it downstream under conditions up to a ten-year storm event. It must be able to bypass all other storms including 100-year event with a discharge rate equivalent to or less than pre-development conditions without negatively impacting the 100-year floodplain above or below the site. If data indicates that the facility can not retain a significant portion of the runoff (95%), then the facility must be designed to detain runoff.
(G) If available, each post-construction SWPPP shall be evaluated for consistency with the stormwater master plan or watershed study for the major watershed or watersheds within which the project site is located. The individual project evaluation will determine if stormwater quantity and quality management practices can adequately serve the property and limit impacts to downstream public and private properties. The presence of a regional facility(s) will be considered in determining the extent to which quantity and/or quality controls will be necessary.
(H) The city reserves the right to require superceding or additional treatment criteria or objectives for specific pollutant(s) as necessary to meet overall storm water quality management program objectives or directives under a watershed improvement or total maximum daily load (TDML) program as administered by the USEPA or the State of Indiana.
(I) On-site BMP coordination with regional BMPs.
(1) All properties are expected to implement on-site stormwater quality control measures, but the extent of application may be reduced given the availability, proximity and nature of regional stormwater quality BMPs.
(2) The extent and type of on-site stormwater quality management practices implemented shall be proportionate to the land use, pollutant discharge potential and proximity to regional stormwater quality management practices.
(Ord. G-06-12, passed 4-20-2006)