Council directs staff to pursue 50‑foot reservoir plan for May Valley after multi‑hour briefing

Moses Lake City Council gave staff policy direction on the size of a planned water reservoir to serve the May Valley area and associated development agreements.

City staff and consultants presented technical and policy tradeoffs for reservoir sizing: the volume of a tank must cover fixed “dead” and operational storage, fire suppression requirements (the fire marshal specified 2,750 gallons per minute for four hours, totaling 660,000 gallons for the site), Department of Health standby storage (a stated minimum of 200 gallons per connection), and equalizing storage to manage peak‑hour shortfalls versus well capacity. Staff explained those buckets determine minimum tank volume more than the average day demand.

The presentation included four scenarios that combined two planning totals (4,500 or 6,000 total ERUs west of the lake) and two irrigation assumptions (100% of units irrigate from city water, or a 50/50 split where half of new connections provide their own irrigation). Staff emphasized that the standby storage requirement (200 gallons per connection by DOH guidance) is the dominant driver as the number of planned connections rises.

Staff’s 2027‑era cost estimates (inflated from a 2023 baseline) placed a 65‑foot tank sized for the highest scenario near $8.47 million, a 50‑foot option at approximately $7.91 million (6,000 units, 50/50 split), and options sized for 4,500 units in the $6.79 million range. Late in the meeting staff re‑ran numbers for an intermediate design; the estimated cost for a rounded 45‑foot diameter tank was about $6.25 million under one scenario.

Following extended discussion of growth rates, irrigation policy, developer responsibility and financing timing, council voted to pursue the staff‑recommended mid‑range option (labeled Option 4 in staff materials): a 50‑foot diameter reservoir sized to serve roughly 4,500 ERUs using the 50/50 irrigation assumption. Councilmembers who preferred a larger design cited long useful life and rising construction costs; those favoring a smaller tank emphasized payback timelines and developer cost allocation.

Staff said the selected sizing will be used in forthcoming development agreements and cost‑sharing calculations with developers in Moses Pointe and Paradise Pointe. Staff will prepare a final cost estimate for project budgeting, update development agreement language accordingly, and report back with proposed funding and timing options.