Yearlong pumping test will help define aquifers across Kitsap Peninsula

An unprecedented yearlong pump test of a deep water well in Central Kitsap is expected to provide a wealth of new information about our underground water supplies.

Joel Purdy, hydrogeologist for Kitsap Public Utility District, checks the flow at Newberry Hill Well 2, which is being pumped at 1,000 gallons per minute for a full year. // Photo: Christopher Dunagan

The 900-foot-deep well, off Newberry Hill Road, will be pumped continuously for a year, drawing water at a rate of 1,000 gallons per minute. Drawdown effects of the high pumping rate will be measured in 56 other wells — including those operated by Silverdale Water District, Kitsap Public Utility District, the city of Bremerton, North Perry Water District, Naval Base Kitsap-Bangor and others.

The pump test is designed to better define the extent of aquifers throughout Central Kitsap while increasing the accuracy of a groundwater model developed to predict water supplies across the Kitsap Peninsula.

“This is going to be one of the best data-gathering tests,” said Joel Purdy, hydrogeologist for Kitsap Public Utility District. “Hydrogeologists dream of doing this kind of aquifer test.”

The test well, known as Newberry Hill Well 2, draws its water from the extensive Seabeck aquifer, which is recharged by rains falling on forestlands throughout the central-southwest portion of the Kitsap Peninsula. The pump test, which began July 16, will measure how quickly water can move through the ground by measuring how fast unused wells get drawn down during pumping and how fast they recover afterward.

Silverdale Water District has turned off all of its deep wells and is operating only two shallower wells near Spirit Ridge and Island Lake on the north side of Silverdale. Those wells are providing the extra water needed for people watering their lawns during the summer, said Morgan Johnson, general manager of the water district. Those two wells probably won’t be needed once the fall rains arrive.

During the winter, any excess water from the pumping test will be sent through Silverdale to the KPUD’s Vinland water system in North Kitsap, so all of the water will be used during the yearlong experiment.

Pumphouse and reservoir for Newberry Hill Well 2, the site of a test to measure the extent of the Seabeck aquifer. // Photo: Christopher Dunagan

After a month of constant pumping so far, some slight signs of a drawdown might be observed in a Silverdale well located about 1.7 miles away near Newberry Hill and Dickey roads, Joel told me. In theory, the level in that well should stabilize within three months.

“There is nothing surprising about this so far,” Joel said.

Across the Kitsap Peninsula, various aquifers are generally defined by horizontal layers containing sand and gravel, which can hold water and allow it to move relatively freely through that layer. The aquifers are separated from each other by horizontal layers of fine-grain clay and silt that do not transmit water as readily.

The Seabeck aquifer is believed to be connected to aquifers north and east of Silverdale, including Bainbridge Island. It also has a connection to the Manette Peninsula, served by the city of Bremerton and North Perry Water District. The pump test, which involves monitoring wells at various depths, should help determine how readily the water moves horizontally through the entire region, as well as how readily the water moves from one layer to another.

In 2016, the U.S. Geological Survey completed development of a computer-based groundwater model that can be used to predict how much water is available in wells and streams, based on geological conditions and the amount of rain that falls in a given area. See Water Ways, March 12, 2016.

There are some indications that the USGS model over-estimates the rate that rainfall infiltrates into the ground and passes through the various aquifer levels, Joel said. By using the pump test for calibration, the model’s flow rate to deeper aquifers can be made more accurate.

The groundwater model is one tool used by experts to determine the effects of drilling a new well in a given area. Water must be available before the Washington Department of Ecology will issue a new water-rights certificate. Consideration must be given to any effects on nearby streamflows, which are maintained for salmon and other aquatic creatures.

The pump test is being conducted as a partnership between the KPUD and Silverdale Water District, which jointly operate the test well under a recently signed agreement. The partnership hired Aspect Consulting of Bainbridge Island to predict the outcome of the pump test based on the USGS groundwater model. Aspect will analyze the data from the test and prepare a report with recommendations once the test is complete next summer.

Newberry Hill Well 2 was drilled 18 years ago, but it has never been operated as a full-time production well. A joint agreement between the water district and KPUD allows each water purveyor to take an equal amount of water, up to 500 gallons per minute. The well can be used to supplement existing water supplies in the Silverdale area, and the KPUD has authority to move the water through Silverdale to North Kitsap, thanks to pipelines connecting the various water systems.

It is all part of a long-range plan, Morgan Johnson said.

“People have been asking, ‘Why are you building large pipelines from Silverdale to the rural areas? You are promoting growth,’” Morgan said. “I tell them, ‘No, we are not promoting growth; we are planning to bring the water to the development.”

The goal, established years ago by Kitsap County, the KPUD and regional water systems, has been to concentrate new development in urban areas and protect the environment in rural areas, as called for by the state’s Growth Management Act. With that in mind, water can be moved from the outlying forested areas by way of the aquifers themselves or through pipelines. By managing the water carefully, population growth can be accommodated for the foreseeable future.

The yearlong test will provide important information about the capacity and extent of the aquifers. That will help water managers ensure an ongoing supply for humans as well as fish and wildlife.

2 thoughts on “Yearlong pumping test will help define aquifers across Kitsap Peninsula

  1. I’m sure I’m coming to this conversation late….but how odd this all sounds. How can it be that a water district decides to do a yearlong drawdown test on an interconnected aquifer system that might give them results they need for a test but could negatively affect homeowners throughout Central Kitsap who have their own wells? Granted, they are already drawing water from their well, but to intentionally draw extra water to complete this test makes little sense. Why don’t they put the extra water back into the aquifer that benefits us all? What happens when the wells in Seabeck, let’s say, run dry due to this drawdown test? I read this today in the Sun…may have missed other stories but I think this sounds like a bigger issue than it’s being made out to be.

    1. Most private wells are not nearly as deep as the well being pumped. They are essentially in separate aquifers, so the effect is expected to be minimal. I understand that wells at all depths are being monitored to see how much, if any, effect is seen. No problems are expected from this temporary drawdown, but the whole experiment could be called off if problems arise.

      In case there is any confusion, the water is all being put to use in households and businesses in the region. Other wells in the Silverdale water system have been turned off during the test. If there is excess water from the pumping at any time, it can be directed into a system operated by Kitsap Public Utility District.

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