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CR 97-221 Consider 6th Ave N Storm Sewer Improvement\ ~ G / ~w~- ~ ¢{I~~ December 1, 1997 ti ~ P K , ~ ~ Council Report 97-221 Consider 6~ Avenue North/3`~ Street North Storm Sewer Improvement Project Proposed Action. Staff recommends adoption of the following motion: Move that Council approve 6~ Avenue Nortb/3`~ Street North storm sewer project, as presented. Overview. RCM Associates, Inc, has completed the feasibility study and report. This Council report summarizes the most important features of the report and provides the proposed funding method. In additioq RCM will present an overview of the report at the Council meeting. Staff is seeking City Council approval of the recommended project scope. Primary Issues to Consider. • Project Design Alternatives and Estimated Major Storm Impacts • Recommended Project Alternative • Additional Ponding Areas • Floodproo6ng • Project Funding • Project Schedule Supporting Information. • Feasibility Report v Steven J. Stadler, Public Works Director Council Report 97-221 Page 2 Analysis of Issues. Project Design Alternatives and Estimated Storm Impacts The different alternatives, estimated costs and estimated stormwater depths are shown on Exlribit 14 of the report. In all but the "do nothing" alternative, the greatest variation in stormwater depths occw at 1~` Street North and 6~` Avenue North. Of course, along with varying stormwater depths, there aze different numbers of homes and garages impacted by the major storms. There aze an additional 12 structures impacted at 1~` Street North by a 100-year rainfall event under alternative 1 (36" pipe) versus alternative la (36" pipe with stormwater ponding). • Recommended Project Alternative Staff concurs with the consultant's recommendation of Alternative la. The modeling shows that this alternative provides dramatic improvement from the current situation at 3`d Street North. Additionally, it is the only alternative which doesn't show an increase in flood levels from present at 1~` Street North. • Additional Ponding Areas Detailed analysis and modeling of additional ponding areas has not been done to-date. After a cursory review, the consultant believes that the various limitations in the proposed ponding azeas would result in ponds providing only negligible improvement in overall project results. Nonetheless, the staff request for additional engineering fees (Council Report 97-219) includes a $1,200 item to analyze and quantify improvements. Council Report 97-221 Page 3 • Floodproofing The need for floodproofing of homes in both azeas will be determined as a part of the detailed design of the improvement. Staff proposes to present this information to Council at a future date. At that time, estimated costs would be available to help Council decide on a policy for funding this work. • Froject Funding Staff proposes to fund this project and improvements in the other problem azeas with a combination of storm sewer utility funds and a $600,000 inter- fund loan from the sanitary sewer utility fund. This combination of fimding will provide up to $850,000 in 1998 improvement project funds. A storm sewer utility rate increase will be necessary to pay back the inter-fund loan and bring the fund into a positive cash balance. The loan payback schedule would be 20 yeazs at $42,000/year beginning in 1999. The fund has been carrying a negative cash balance since 1990. The proposed rate increase is $.10/Residential equivalent factor (REF) per year for five years (1999 - 2003). The impact of a $.10 increase on the various land use classes is shown below. Land Use Single Family & Duplex Multiple Family residential Commercial Industrial 1998 Rate per month $3.065/unit $27.60/acre $46.00/acre $46.00/acre Rate with $.10 increase $3.10/unit $27.90/acre $46.50/acre $46.50/acre The current storm sewer utility rate is $9.00/REF. The proposed 1998 budget rate is $9.20/REF. The last storm sewer utility rate increase was a $1.50/ REF in 1993. • Project Schedule The project schedule is shown on page 29 of the feasibility report. The estimated construction completion date is August 1, 1998.