CCP 09-10-2001 - Laserfiche WebLink

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I I I I I I I . I I I I I I I {' I 9.7,01 The importance of Table 10 relates to both the total capital cost comparison and unit cost (per cubic foot of storage). The SEH estimate is very close to the USEPA estimate (2.8%) for the same BMP. In addition, the unit cost is on the low end of the reported literature. The economic benefit cost is difficult to quantify from "balance sheet" perspective for this BMP. The ideal approach would specify a chain of events: pollutant loading reductions from construction of the ponds; the physical-chemical properties of the receiving streams and consequent linkages to biologic/ecologic responses in the aquatic environment; and human responses and values associated with these changes. The necessary data does not exist to conduct such analysis. Instead, the benefits can be outlined in terms of: l. Effectiveness of reducing pollutant loads; 2. Direct water quality impacts; and 3. Economic benefits or costs. The primary function of the proposed detention ponds is to reduce pollutants. They are very effective at removing total suspended solids (often 90%+ efficiency), total phosphorus (up to 60% removal) and other associated pollutants (heavy metals and hydrocarbons. Thus, their track record and performance has been documented in various studies, but must be constructed properly and maintained. Water quality impacts reduction was detailed in the Lake Josephine project previously discussed in the Plan. Direct water quality improvement was achieved through the use of an existing wetland/pond to treat the incoming storm water. The economic benefit or cost for the Lake Josephine project has not been evaluated, although methods exist for such an analysis. A positive benefit has been achieved versus a "no built" approach that could have been taken. Loss of recreational usage (swimming, boating, and aesthetics) would likely have continued to decrease in Lake Josephine in the absence of this project. Amendment Procedures The Arden Hills Local Stormwater Management Plan is intended to extend through the year 2011. For the plan to remain dynamic, an avenue must be available to implement new information, ideas, methods, standards and management practices. Persons either residing or having business within the City shall be able to request amendment proposals at any time. City of Arden Hilis, Minnesota Local Water Resource Management Plan A-ARDEN0101.00 Page 47