Notwithstanding applicable federal and state stormwater quality requirements imposed during construction, the following measures shall be applied, relating to post construction stormwater management.
(a) The quantity of impervious surface shall be minimized as practical for the proposed principal use.
(b) Best management practices (BMP) shall be employed to minimize off-site stormwater runoff, increase on-site infiltration, encourage natural filtration, simulate natural drainage patterns and minimize off-site discharge of pollutants to surface water. BMP may include measures such as detention and retention basins, recharge trenches, porous paving and piping, control terraces, rain gardens and swales, flattening of drainage slopes or other measures having widespread acceptance or endorsed by the Kansas Department of Health and Environment.
(c) The calculated peak rate of stormwater run-off that would be directed off-site upon full development of a proposed subdivision, or after the proposed development of a single tract, shall not exceed the peak rate of stormwater run-off that exists prior to such development. Calculations shall take under consideration any contributing runoff from areas adjacent to or upstream from the site. The peak rate of stormwater runoff shall be determined upon application of the design criteria contained under Section 4 of the 2008 Wamego Stormwater Master Plan, prepared by Wilson & Co.
(d) Where on-site measures to reduce the peak run-off rate to pre-development levels are deemed to be impractical, determination of required off-site improvements shall be made by an engineer, duly licensed by the State of Kansas, and shall be made at the expense of the developer. The Planning Commission shall review and recommend Governing Body approval of one of the following approaches:
(1) Off-site measures, including detention on public right-of-way or on property owned by others, where suitable approvals and agreements running with the land are in place, setting forth financial responsibilities for the constructions of such measures and setting forth the party responsible for their continued maintenance.
(2) Off-site improvements to stormwater facilities and channels owned by private parties, where suitable approvals and agreements running with the land are in place setting forth financial responsibilities for the construction of such improvements, and setting forth the party responsible for their continued maintenance by the developer.
(3) Off-site improvements to stormwater facilities and channels owned by the city or another public agency, at no cost to the city, provided that the Governing Body approves such alterations to city owned public facilities, or that any necessary approvals required from other public agencies are secured.
(e) Where the amount of storage capacity can be increased to provide a benefit to the public, as in cases where a channel draining other properties and streets passes through the subject property, negotiations for public participation in the cost of development may be feasible.