09-22-2004 Council Agenda - Laserfiche WebLink

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WCA/CWA Wetland Application Gervais Hills GES Project No. 2004.040 June 16, 2004 Page 3 Total Wetland Avoidance Alternatives Given the size of the parcel and the position of the wetland, a viable development cannot occur on the site without impact to the wetland. Although it is possible to avoid the wetland impact, it is not practicable or feasible for several reasons. First, the quality of the wetland must be taken into account when considering the practicality and feasibility of avoidance. The use of this wetland as a stormwater conduit has apparently been the main factor in the wetland plant community being dominated by reed canary grass and other invasives such as box elder. The only native species which could be considered to be "dominant" is river bulrush which is tolerant of changes to water quality and sedimentation. Native species in the wetland appear to be on the decline while the more invasive species are probably increasing their coverage. When considering the practicality and feasibility of avoidance, it is also necessary to consider the avoidance alternative's economic impact on the project. To avoid the wetland, which has been demonstrably degraded, would result in the loss of five of the proposed 12 residential units. Although it is understood that economic arguments alone cannot be used to dismiss an avoidance alternative, decreasing the buildable lots by 42 percent would render the project infeasible and is not practicable when considering the wetland quality. Much of the wetland impact is due to the creation of on -site wetland mitigation basins which will also serve to manage and treat stormwater flowing to Gervais Lake. Most of the water entering this site is not the result of the project but is existing runoff from off -site. The mitigation plan will help to attenuate stormwater flows and will provide water quality benefits for Gervais Lake. The implementation of the plan will reduce the existing peak stormwater runoff rate and thereby reduce flooding potential. Impact Minimization The proposed impact cannot be further minimized. Slopes from the proposed fill area for the street and residential pads cannot be steepened without creating the potential for erosion and the compromising of the stability of the street and residential pads. Rectification of Impact No temporary wetland impacts are proposed which could be rectified after project completion. Reduction or Elimination of Impacts Over Time A Storm Water Pollution Prevention Plan and a Grading, Drainage and Erosion Control Plan have been developed by the project engineer which will reduce the impacts to downstream waters through erosion control and water quality treatment measures.