Town water supply hard to assess

"Coupeville is surrounded by water, but the water that really counts is all underground. The ability of the town’s aquifers to provide a constant supply of water not only guarantees the quality of life for the town’s 1,580 residents. It enables Coupeville to meet growth projections — 320 additional residents by the year 2,020 — mandated by its Comprehensive Plan and the county-wide planning policies adopted by Island County in 1998.But predicting how much water Coupeville aquifers have — or will have in the future — is at best an imprecise science. In fact, it’s as difficult as predicting the weather — which is relevant, because the town’s aquifers are totally dependent on rain for replenishment. Additional hard-to-assess factors include how well and how much rainwater sinks into and flows through the soil and the town’s the ability to pump, filter and transport the water.Still, Coupeville has to gauge its water supply somehow.So the town gathers information from a slew of public and private agencies before making an educated guess about the water supply. And then it predicts the future.Besides its own Public Works Department, Coupeville employs or interacts with four other private, local and state agencies to determine its water supply, said Coupeville Public Works Director, Larry Harmon.One of those agencies is AGI Technologies, a private environmental consulting firm based in Bellevue, Wash.“AGI looks at existing wells in the area,” Harmon said. “They do some testing, use existing information in the area, and determine how much water is potentially available in the aquifers.”One of the ways AGI accomplishes this, said company hydrogeologist Scott Coffey, is to conduct pumping tests.With those, AGI can determine the capacity of the wells and aquifers, the speed at which water flows through the ground, and prepare water budgets, or projections on the available supply.One of the key factors in preparing water budgets is being able to predict annual rainfall, Coffey said, and that is accomplished by looking at weather records over the past 50 to 100 years. “You can start to see patterns with information like that,” Coffee said.AGI also looks at something called a water balance — how effectively rainwater soaks into the ground before it evaporates. Usually, Coffey said, that’s less than half the amount that falls.Other factors include transmissivity, how easily water flows through the ground; and recharge rate, how long it takes the aquifers to recharge themselves.After compiling this and other information, AGI prepares a report that Coupeville uses in the next step — submitting water rights requests to the Washington State Department of Ecology.“The town hires AGI and its hydrogeolists to provide necessary evaluations to the Department of Ecology ,” Harmon said. “Those reports are given to the Department of Ecology so they can make a determination on water rights requests that the town has made and they’ll challenge some of the information in AGI’s report.”Then Harmon and the town go about substantiating the claims in the reports.Once the DOE is satisfied Coupeville has the water it says it has, they either grant or deny water rights requests. Then the Washington State Department of Health steps into the cycle.The Department of Health is “mainly interested in whether you can provide adequate service to your customers,” Harmon said. “They’re mainly looking at the quality and quantity of your water as well as the distribution system and storage tanks, the ability to provide good service to your customers.”Derek Pell, a regional engineer for the Washington State Department of Health’s Northwest Drinking Water Operations, said the department uses a Water System Plan. “It asks them to demonstrate how they’ll serve customers currently and in the future. And if you can provide that, they’ll determine how many hookups you can provide service to in your operating permit with them.”Pell said that because the Division of Drinking Water reviews municipality’s water plans, they rely on the Department of Health’s review and approval process to verify there is sufficient capacity to support additional connections.“When they get their water rights, they go to a design engineer who would figure a way to pull water from the source and deliver it to the customers. My role is to work with the engineer and approve the plan for delivery,” Pell said.Using its available science and sources, Coupeville has determined it does have enough water to supply its 1,580 current residents and the 320 people projected to move there by the year 2020.That works out to 1,067 water connections in use now, and allows for a reserve supply of 174 more connections in the future.Harmon admits the science of divining Coupeville’s water isn’t exact, but he feels it’s adequate for now. Plus, it’s subject to change.“You can manage the system, it isn’t static,” he said. “If our water use starts changing, we can drill more wells as we already have the land. In the worst case, we could tighten things up to conserve more water.“I’m comfortable with the projections,” he added. “the only thing that’s scary is if you lose some of the wells and I don’t see that happening. Most of the town’s wells have been in existence for a long time and have a pretty proven track record.” "

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