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Council hears Western Sanitary Sewer study; approves additional hydraulic analysis
Summary
Council received a city-commissioned Western Sanitary Sewer study describing two alternatives for a western area and a southern area, reviewed estimated costs and potential assessments, and approved a $17,000 hydraulic analysis (plus $5,500 third‑party flow study) while removing an added 10% contingency.
City staff and consulting engineers on Feb. 3 presented results of a Western Sanitary Sewer Study that examined sanitary‑sewer options for two unsewered areas west and south of Oconomowoc and asked the Common Council to authorize a follow‑up hydraulic analysis.
Consulting engineer Stan Sugden introduced Abby Hanson and Dave Arnott, who walked the council through two alternatives for the Western (Bridal Road) area: Alternative 1 would use gravity conveyance to a single lift station and a force main; Alternative 2 would use a combination of gravity mains and low‑pressure grinder pumps for low‑density sections with a different lift‑station location. ‘‘Our primary focus was achieving gravity collection with a minimum velocity of 2 feet per second,’’ Hanson said while summarizing the layout provided by city staff.
Arnott said both Western alternatives would require a lift station sized at approximately 750 gallons per minute; his cost estimate for the lift stations and associated force mains was $1,180,000. Total capital plus operation and maintenance for Alternative 1 was presented at roughly $9.7 million and Alternative 2 at about $10.5 million; staff estimated the city’s backbone cost (force main, lift station, and mainline sewer to be assessed) at just over $4.3 million.
For the southern study area (south of Valley Road), Hanson and Arnott presented two comparable alternatives with smaller lift stations (300–400 gpm), a lift‑station cost estimate near $975,000 and total capital+O&M shown at about $6.9 million. Arnott said upgrades to the Concord Road lift station would be needed (estimated at roughly $645,000) to accept pumped flows.
Council then considered a separate resolution requesting a hydraulic analysis from the current study limits (just east of the Concord bridge) back to the wastewater treatment plant and authorized field verification using area velocity meters. The proposal as presented listed $17,000 for the analysis plus a $5,500 third‑party fee; council debated a standing 10% contingency in resolution language and ultimately voted to approve the hydraulic analysis while removing the 10% contingency for this scope of work.
Staff emphasized the study is conceptual and intended to give developers and the city a clear picture of what infrastructure would be required if development proceeds; staff estimated a conservative implementation timeline with potential operation by 2027 if design and construction move quickly or sooner if a developer leads a specific project.
What the council approved: authorization to proceed with the hydraulic analysis and field flow verification, with the motion amended to remove the 10% contingency. Staff will return with further design, procurement and financial recommendations as the project advances.
