SECTION 6.06. STORM WATER MANAGEMENT STANDARDS.
(1) STORM WATER DISCHARGE QUANTITY. Unless otherwise provided for in this ordinance, all land development activities subject to this ordinance shall establish on-site management practices to control the peak flow rates of storm water discharged from the site as described in this ordinance. Infiltration of storm water runoff from driveways, sidewalks, rooftops, parking lots, and landscaped areas shall be incorporated to the maximum extent practical to provide volume control in addition to control of peak flows.
[a] On-site management practices shall be used to meet the following minimum performance standards. All developments in the Village shall not increase peak flow rates of storm water runoff from that which would have resulted from the same storm occurring over the site with the land in its pre-development (6.05) conditions for design rainfall events with recurrence intervals of two (2), ten (10) and one hundred (100) years.
[b] All storm water conveyance systems within the proposed development receiving storm water runoff from the proposed development, shall be designed to completely contain peak storm flows as described in 6.06(1)(b)(i) and (ii) below. Calculations for determining peak flows for conveyance system sizing shall be based on the existing or future proposed land use conditions for off-site areas (whichever results in the highest peak flows), and the post-development land use conditions for the on-site areas.
 For open channel conveyance systems the peak flow from the 25-year storm shall be completely contained within the channel bottom and banks.
 For storm sewer pipes the peak flow from the 10-year storm shall be completely contained within the pipes with no surcharging or pressurized flow.
[c] Determination of peak flow rates and volume of runoff for purposes of meeting the requirements of Sections 6.06(1)(a) and (b) shall be computed by procedures based on the principals and procedures approved by the Village of River Hills Municipal Code, AWisconsin Construction Site Best Management Practice Handbook@, ANational Resources Conservation Service, Urban Hydrology for Small Watersheds, Technical Release 55 (TR-55)@ and the Wisconsin DNR.
[d] More stringent discharge limits may be required at the discretion of the Village for reasons such as, but not limited to insufficient downstream system capacity, potential erosion of stream channels, or impacts on flood stages.
[e] All discharges will be restricted to public drainage systems (including storm sewers and ditches) or to waters of the State. It shall be the responsibility of the applicant to obtain, from adjacent property owners, any easements or other necessary property interests concerning flowage of water from the proposed development onto private lands.
[f] Increases or decreases in the hydrology of natural wetlands shall be minimized to the extent practical. Where such changes are proposed, the impact of the proposal on wetland functional values shall be assessed using methods acceptable to the Village and Wisconsin DNR. Significant changes to wetland functional values shall be avoided as defined by Wis. Adm. Code NR 103.
(2) STORM WATER DISCHARGE QUALITY. Unless otherwise provided for in this ordinance, all land development activities subject to this ordinance shall establish on-site management practices to control the quality of storm water discharged from the site. On-site management practices shall be used to meet the following minimum standard established for each development District: (management practices may be as set forth in the Wisconsin Storm Water Manual, Part 2, Technical Guidelines for Storm Water BMP’s)
[a] Storm water management measures shall be designed to remove on an average annual basis a minimum of 80% of the total suspended solids load from the proposed on-site development when compared to the proposed on-site development without storm water management measures.
[b] Storm water management measures for redevelopment shall be designed to remove on an average annual basis a minimum of 40% of the total suspended solids load from the proposed on-site redevelopment when compared to the proposed on-site redevelopment without storm water management measures.
[c] Discharge of urban storm water pollutants to natural wetlands shall have pre-treatment and vegetative buffers, unless otherwise exempted by the Village and Wisconsin DNR. Significant changes to wetland functional values due to storm water pollutant loads shall be avoided.
[d] Storm water discharges shall have pre-treatment prior to infiltration, to prolong maintenance of the infiltration practice and to prevent discharge of storm water pollutants at concentrations that will exceed groundwater preventive action limits or enforcement standards established by the Department of Natural Resources in NR 60 Wis. Adm. Code. Storm water infiltration is prohibited under the following circumstances:
 Storm water is generated from highly contaminated source areas at manufacturing industrial sites;
 Storm water is carried in a conveyance system that also carries contaminated, non-storm water discharges;
 Storm water is generated from active construction sites. Land disturbing activities shall comply with the Construction Site Erosion Control requirements of the Village Code.
[e] Storm water ponds and infiltration devices shall not be located closer to water supply wells than indicated below without first notifying the Village:
 100 feet from a non-public water supply well;
 1,200 feet from a community water supply well;
 the boundary of a recharge area to a well identified in a wellhead area protection plan.
[f] More or less stringent treatment limits may be required on a site-specific basis, at the discretion of the Village.
(3) EXCEPTIONS. The Village may waive the minimum requirements for on-site storm water management measures established in 6.06(1) and (2) upon written request of the applicant, provided that at least one of the following conditions applies:
[a] Alternative minimum requirements for on-site management of storm water discharges have been established in a Storm Water Management Plan that has been approved by the Village and that is required to be implemented by local ordinance.
[b] Provisions are made to manage storm water by an off-site facility. This requires that the off-site facility is in place, is designed and adequately sized to provide a level of storm water control that is equal to or greater than that which would be afforded by on-site measures meeting the requirements of this ordinance, and has a legally obligated entity responsible for long-term operation and maintenance of the storm water measure.
[c] The Village finds that meeting the minimum on-site management requirements is not feasible due to site restrictions.
(4) FEE IN LIEU OF ON-SITE STORM WATER MANAGEMENT MEASURES. Where the Village waives all or part of the minimum on-site storm water management requirements under 6.06(3)(c), or where the waiver is based on the provision of adequate storm water facilities provided by the Village downstream of the proposed development, or as provided for under 6.06(3)(b), the applicant shall be required to pay a fee in an amount determined in negotiation with the Village. In setting the fee for land development projects, the Village shall consider an equitable distribution of the cost of land, engineering design, construction, and maintenance.