The City engaged Wood Environment and Infrastructure Solutions to perform a review of our municipal separate storm sewer system MS4 in light of best practices followed by other stormwater utilities. During the course of this MS4 review, the City was successful in obtaining a grant from the Kansas Department of Agriculture (KDA) to do a two dimension model of the City’s stormwater runoff. Based on Wood’s review of the MS4 program, and the results of the modeling, we are recommending several revisions to the stormwater code. Revisions include the following:

TMC 13.25 Stormwater Utility / Stormwater fee discount – The revisions simplify the method for determining the amount of discount for water quantity, adds a potential discount for water quality, but leaves the total discount capped at 40%.

TMC 13.35 Stormwater Management / Stormwater quality – The requirement clarifies that water quality Best Management Practice (BMP) designs will require the use of a level of service based methodology. Additionally, the revisions clearly address the need for control of both stormwater quantity and quality. Also, the revisions authorize the Director to implement a handbook for stormwater BMP design. The handbook is targeted for the design community and provides guidance for designers in preparing stormwater management plans. The revisions also require the owner/developer to provide an as-built plan for the completed BMPs, as well as provide for a final inspection by City staff.

TMC 13.40 Stormwater BMP Maintenance (NEW) – This new chapter reaffirms the existing code requirement that property owners are responsible for the long term maintenance of BMPs on their property. Additionally, it requires owners to periodically inspect their BMPs and to submit an inspection report to the City once every two years. Once every six years the inspection report must be performed by an engineer or landscape architect. If the owner fails to submit a report, he or she will not be eligible for a stormwater fee discount. To assist the owners with the inspection, this section authorizes the Director to implement a Property Owners Guide to Stormwater BMP Maintenance. The BMP maintenance guide is a visually based guide written for a property owner, to explain the basics of BMP operation and maintenance and includes inspection forms.

TMC 17.10 Buffer Areas / Stream Buffers – The revisions to this section replace the existing stream buffer widths based on stream type, with a science based buffer that establishes buffer width on stream size, slope, soil type and physical conditions. We will follow up the revisions by adding the new stream buffer to the City’s GIS system for use by the development community. The development of the stream buffer model was a product of the KDA grant funded modeling done by Wood.

TMC 17.30 Floodplain Management – The revisions to this section include requiring that any development in the AH ponding areas, identified as part of the levee certification, will require corresponding cut to maintain the overall storage volume. Additionally, development in the floodway fringe of greater than 5,000 SF will require modeling to determine no rise, as well as compensatory cut to offset any fill.

TMC 18.235 Landscape Requirements – The revisions to this code section clarify that certain BMPs are eligible for credit towards the landscape points, required under the zoning regulations. ‘Green’ BMPs that promote native vegetation, and provide evapotranspiration and soil stability, are eligible for higher credit than other BMPs that reduce impervious area or provide for infiltration or detention.