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<br />Shenandoah Improvements Feasibility Report <br />City of Lino Lakes, MN <br />WSB Project No. 018901-000 Page 20 <br />BMP Option Ditch 100 -yr <br />HWL <br />HWL <br />Decrease (ft) <br />TSS Removal <br />(lb/yr) <br />TP Removal <br />(lb/yr) <br />Existing 892.15 N/A N/A N/A <br />Concept 1 891.44 0.72 758 4.21 <br />Concept 2 891.29 0.87 1,416 9.05 <br />Concept 3 891.31 0.85 1,297 8.37 <br />Concept 4 891.31 0.85 5,688 19.75 <br /> <br />A major component of assessing BMP cost efficiency is the estimated cost divided by <br />the provided pounds of TP removal. The proposed improvements were evaluated with <br />a 25 -year lifespan. Costs over the lifetime included full construction cost, 5 years of <br />vegetation maintenance, annual BMP maintenance, and any major maintenance <br />costs. These costs and the price per pound of TP are summarized in the table below. <br />BMP <br />Option <br />Annual TP <br />Removal <br />(lb) <br />Construction <br />Cost <br />5 -year <br />Vegetation <br />Maintenance <br />Cost <br />Annual BMP <br />Maintenance <br />Cost <br />Major <br />O&M <br />Cost <br />25-year <br />Cost/Pound <br />TP <br />Concept 1 4.21 $170,250 $42,880 $100 $0 $2,049 <br />Concept 2 9.05 $410,000 $42,880 $200 $0 $2,024 <br />Concept 3 8.37 $455,350 $42,880 $200 $0 $2,405 <br />Concept 4 19.75 $601,000 $42,880 $300 $45,000 $1,410 <br /> <br />All concepts proposed provide improvements in varying degrees. Concept 1 provides <br />lower benefits but comes at a lower cost and would entail a smaller amount of <br />disturbance to existing site conditions. Concept 2 maximizes basin size and <br />a ssociated pollutant removals, but at an increased cost and with no broader <br />improvements to the park. Concept 3 provides large basin sizes, ditch realignment <br />similar to a natural channel, and potential recreational benefits, but with a greater <br />cost and major site disturbance. Concept 4 provides similar benefits in addition to <br />the best cost per pound of TP removal, but at a significant upfront cost and higher <br />long term maintenance needs. <br />This report recommends the City consider the improvements in Concept 4. The <br />proposed work w ould allow for high degrees of wetland improvements in large basins <br />that would also serve to reduce flood levels. Ditch realignment would further serve <br />to enhance these natural resources benefits while also providing options for a <br />greenway trail system and educational opportunities around the merits of stormwater <br />treatment and wetland ecosystems. Finally, the proposed IESF would provide <br />exceptional pollutant treatment and the best price per pound of TP removed. With <br />the wide degree of benefits and greatest price -quantified water quality improvement, <br />Concept 4 would also be a strong candidate to receive grant funding to help the City <br />offset its construction costs. However, WSB will be happy to support the City in <br />pursuing further design of any concept propose d.