The City of Beaverton has one of the most successful municipal ASR (aquifer storage and recovery) programs in Oregon and uses it to supply about 25 percent of its summer peak water demand.

Background

In the early 1990s, the City of Beaverton was examining its future water supply capacity against the anticipated increase in new residents and business in the area, and the increasing regulatory barriers to obtaining new water supplies such as stream flow requirements, designation of Critical Groundwater Areas, and the over-drafting on aquifers. The City wanted to evaluate and test aquifer storage and recovery (ASR) to help offset its peak demands.

GSI’s Solution

The City had an existing well (ASR No. 1) and pump station that had been out of service for more than 15 years. In order to determine if the well could be used for the City’s planned ASR program, GSI conducted an ASR feasibility study. Because the well had been offline for so long, the feasibility study focused on assessing the condition of the well and conducting pre-pump testing to determine if the well was capable of an actual pump test.

GSI also conducted an evaluation of groundwater users in the area, evaluated hydraulic design, and conducted a hydrogeologic assessment and aquifer performance test. This was done in order to map the subsurface conditions in the area and to potentially find nearby monitoring wells that could be used during a future pump test.

Results of the well assessment and subsurface investigation indicated that an aquifer test was feasible to further evaluate the capacity of the aquifer.  In order to complete a fatal flaw analysis, a water quality comparison of the native groundwater and the likely ASR injection source water was conducted to help determine if there would be any water quality issues that would impact a successful ASR program. Additionally, a numerical groundwater model of the proposed ASR site was developed and evaluated to support a wellhead protection plan.

These initial studies showed that the well was capable of more than 1 million gallons per day (mgd) recovery capacity and would have more than 100 million gallons of storage capacity during a typical annual operation period. Because of the promising study results, GSI retrofitted the existing well for the City’s first ASR operation location. In 1998, ASR No. 1 was brought online and added to the City’s water supply portfolio.

Given the success of the City’s first ASR well, GSI then designed two new deep groundwater ASR wells (ASR No. 2 and ASR No. 4) in the Columbia River Basalt Group aquifer. Combined, the three ASR wells (located at the City’s Sorrento Water Works facility) met more than 25 percent of the city’s peak summer demand by supplying up to 6 million gallons per day (mgd).

Since its first ASR well was brought online, GSI has also been providing the City with ASR on-going operational support which has included filing the City’s ASR Limited License Extensions, water level monitoring, water quality monitoring and control, monitoring groundwater seeps, and long-term monitoring and data management, yearly reporting, and assisting the City apply for an ASR operational permit in 2013.