5.1. SR 03-14-2011 - Laserfiche WebLink

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Elk River Subwatershed ER04W: Stormwater Retrofit Assessment Page 3 The following table ranks retrofit projects identified in this report. In ranking projects, a number of factors were considered including the level of treatment, the cost per pound of phosphorus treated and the projected feasibility of doing the project. Feasibility included a subjective estimate of the level of participation of private land owners and the estimated total cost of the project. The percent TP reduction reflects a percent reduction for the catchment. Because catchment areas range from 13 to 238 acres, the percent TP reduction is not useful for comparing the level of treatment between catchments. For that reason, the Ibs/yr of TP reduced was used to compare water quality benefits between projects. Not all treatment options listed in the catchment profiles are ranked. The treatment options selected for ranking were based on site constraints for sites identified, an estimate of public participation and also total project cost. Catchment or Pond ID Retro Type Qty of 100 ft3 BMPs TP Reduction (%) TP Reduction (Ib/yr) Volume Reduction (ac-ft/yr) Overall Est. Cost' O&M Term (years) Total Est. Term Cost/Ib- TP/yr2 ER04~'V1' PM NA 1% 1.8 0.0 $2,250 30 $42 ER04W2 RG 25.3 30% 13.4 12.5 $33,084 30 $224 ER04W4 RG 17.8 1590 8.2 7.8 $24,173 30' $:261. ER04W3 RG 15.6 16% 7.0 6.3 $21,474 30 $269 ER04W5 RG 2.1.9 ~ 30% 6.2 4.8 $29,013:.: 30 $421 ER04W5 RG, IF 28.2 36% 7.5 5.8 $48,534 30 $595 ER04W1" FtG 24.4 2% ' 3.2 7.5 $32,009 30 .$905 ER04W1 PM 4,086 4% 10.9 0.0 $211,638 30 $931 RG= Rain Gardens (eioretention, infiltration and/or filtration) IF =Underground filter and infiltration (tree planter infiltration boxes) F=Filtration (sand curtain, surface sand filter, sump, etc) IR =Impervious (cover] Reduction PM = Pond Modification (increased area/depth, additional cells, forebay, and/or outlet modification) PS =Permeable Surface (infiltration and/or filtration) VS =Vegetated Swale (wet or dry) WD = New wet] Detention or Wetland creation lEstimated overall costs include design, contracted soil core sampling, materials, contracted labor, promotion and administrative costs (including outreach, education, contracts, grants, etc), pre- construction meetings and installation oversight. ZThe total estimated term cost/Ib-TP/yr includes overall cost plus a 30 years of operation and maintenance cost divided by 30 years of treatment.