To: Honorable Mayor and Members of Town Council
From: Mark Marlowe, P.E., Director of Castle Rock Water
Matt Benak, P.E., Water Resources Manager
Heather Justus, P.G., Water Resources Project Manager
Title
Update: Aquifer Storage and Recovery (ASR) Program
Body
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Executive Summary
The purpose of this memorandum is to update Town Council on Castle Rock Water’s Aquifer Storage and Recovery (ASR) program and the projects that make up that program. ASR is defined as the ability to store water in an aquifer and recover that water through pumping when needed. The ASR projects are a key piece of Castle Rock Water’s (CRW) long-term renewable water plan, as they will allow us to store our renewable water in the aquifers during times when excess renewable water is available and then use that water during periods of high demand (e.g. summer demand periods or in times of drought). ASR allows us to store water without evaporative losses (18% annually in our area for surface storage), and also boost hydrostatic pressure which increases pumping capacities in surrounding groundwater wells. In addition, ASR is a very cost-effective storage method at about $2,500 to $3,000 per acre foot compared with surface storage, which is two to five times more expensive depending on local factors. The only drawback is that water stored via ASR must be treated to drinking water standards before storage and treated again when recovered for use.
CRW’s ASR program started in 2008 and gained real momentum in 2013 with the development of a pilot test program on our first two ASR wells (see Attachment A for full history of ASR work and Attachment B for the location of these wells). CRW has invested $600,000 to-date in testing and developing those two ASR wells, which should provide up to 235 acre feet of storage per year. The source of renewable water for these wells will be East Plum Creek. The primary remaining challenge to putting these wells into use is obtaining a permit from the United States Environmental Protection Agency (EPA). Obtaining a permit from EPA has been an ongoing challenge going back to 2017. CRW has been working closely with EPA in the last several months taking our concerns with permitting all the way to the Region 8 EPA Administrator. We believe a draft permit that is acceptable to CRW should be issued this summer.
Two new wells were drilled near Ray Waterman (see Attachment B) and those wells are under contract for ASR and expected to require $1,230,300 in investment this year for another 400 acre feet of storage per year. These wells will be able to store Water Infrastructure and Supply Efficiency (WISE) water. The plan is for these wells to be permitted under the same permit. CRW’s long-term ASR plan includes converting four existing wells to ASR over the next fifty years, with an ultimate goal of 1300 acre feet per year more of ASR storage. The additional cost for this local ASR program is estimated to be $2.1M over this timeframe bringing total planned investments in ASR to around $4M.
In addition to CRW’s local ASR program, CRW has explored the possibility of ASR in the Lost Creek Basin near our Lost Creek water rights through a grant from the Colorado Water Conservation Board (CWCB). The goal of this program is to store junior water rights off of the South Platte River in the Lost Creek Basin, which would improve the operation of our Box Elder project. This preliminary study work has been done through a partnership with Aurora Water. The next steps in this project are to complete a full-scale pilot test in the Lost Creek Basin.
History of Past Town Council, Boards & Commissions, or Other Discussions
A history has been provided (Attachment A).
Discussion
In the 2019 Analysis and Technical Update to the Colorado Water Plan for the Colorado Water Conservation Board (CWCB), ASR is identified as one of the tools that will help Colorado meet the identified water supply gap in Colorado. Centennial Water and Sanitation District’s operation of their successful ASR program in the Denver Basin Aquifers is a well-known example of ASR in Colorado. For thirty years, Centennial has captured surface water under junior water rights, treated and then injected that potable water into their Denver Basin wells at controlled rates and pressures. This program is key, along with multiple pilot tests including CRW’s pilot test, to showing the viability of ASR and provides the technical basis for additional projects in the Denver Basin.
Based on the Water Resources Supply Demand Model, high population growth trend, aging infrastructure and the need for ASR, CRW continues to stay active in pursuing both local and regional ASR projects. It is important for our community that CRW staff understands the complexities of ASR and advances in technology as we move forward as a community. These advances will allow CRW to remain a leader in the industry and improve efficiencies. With the variability in WISE and renewable water supplies, a storage option is needed when WISE and renewable supplies are higher than demand. One of the solutions is ASR, which is the ability to store water in the aquifer and recover the water through pumping when needed. Currently, CRW has two facilities designed with one under construction and one complete. The first completed facility is located in the Meadows area and is able to receive renewable water from Plum Creek Water Purification Facility (PCWPF). The wells associated with this facility are CR-223 and CR-224. These are the wells on which ASR pilot testing was completed, and we are requesting EPA ASR permitting.
The second facility is the two new wells underway at Ray Waterman Water Treatment Plant, CR-232 and CR-233. The drilling and construction for Wells CR-232 and CR-233 are completed. Hydro is currently completing testing on the new wells. It is important to note that Dominion Water and Sanitation District (DWSD) is a partner with us on the ASR portion of the project. DWSD will be funding the cost of the ASR portion of this project in accordance with our 2016 Water Service Agreement. CRW is pilot testing new technology as a part of this ASR project that will allow energy to be generated when water is injected into the ASR wells. One of CRWs largest expenses is the cost of power to pump water from the aquifers. The decline in water levels increases the cost to pump water. However, through ASR, we can increase the hydrostatic water level which effectively reduces pumping costs. In addition, by adding on the ability to generate green power during injection, CRW would be able to offset some of the pumping expenses. In a white paper that Hydro Resources provided to CRW, DR. Sale with Colorado State University (CSU) theorizes the following: “Using the results…, the following solution and example calculation is advanced for estimating power generation from a flow rate (Q) and total dynamic head (TDH). The result suggests that a single ASR well equipped with the study pump, with a flow of 500 gpm and a TDH of 1000 feet, would generate 48kW of electrical power, enough electrical power for 50 homes.” Power generation only occurs during ASR operations of the wells. This will be the first full scale installation. To our knowledge, this type of pilot project is novel and Hydro Resources has advanced the technologies to a point that it is time to move the testing into a real world environment.
CRW will continue to pursue obtaining a Class V ASR Permit with the EPA. CRW staff hopes that an acceptable solution to CRW’s concerns will be achieved. Once the ASR permit is issued, the permit will allow for additional wells to be added to the permit. This will allow CRW to apply to have wells CR-232 and CR-233 added to the permit through the defined permitting process. The next well facilities are planned in the five year and ten year periods. The best places for the ASR facilities are in close proximity to our renewable sources. At this time, we are planning another location near the Plum Creek Water Purification Facility and another near our local WISE infrastructure (see Attachment B). The timing for each would be as excess renewable supplies are available during the winter months and adequate budget for construction.
The next South Metro Water Supply Authority (SMWSA) ASR regional efforts meeting is scheduled for July 1st. CRW staff plan to continue to be active in these discussions with other regional water providers. CRW will continue to be active in these projects as they fit with CRW’s future ASR plans and goals and are approved by CRW Management and Town Council.
Additionally, CRW plans to continue investigations and future projects with other entities for the potential of ASR projects in Weld County. In the 2019 Analysis and Technical update to the Colorado Water Plan for Colorado Water Conservation Board (CWCB), it identifies that ASR storage in the Lost Creek basin will be an essential part of storing water captured from the South Platte River system. CRW staff and Aurora Water staff have had multiple brainstorming meetings to discuss the viability and opportunity to partner on an ASR project in the basin.
Budget Impact
Through 2018, CRW staff estimate that CRW invested approximately $600,000 in ASR feasibility, pilot testing, and constructing ASR facilities. This investment does not include CRW staff hours for designing, testing, analyzing, and preparing memos, reports and applications. In 2019, CRW began design of the two new ASR wells CR-232 and CR-233 at Ray Waterman. CRW staff estimate that the project cost estimate associated with ASR is approximately $1,230,300. This will bring the total Town investment in ASR to $1,830,300.
Staff Recommendation
CRW continues to believe that ASR is an important aspect for storage of our excess renewable water and will aid in meeting our expected future high water demands. Additionally, ASR will help with declining water levels in the Denver Basin and increase well efficiencies and reduce power consumption. CRW staff support innovations and exploring new technologies as they become available to our community, and as the new technology fits with our values and goals.
Attachments
Attachment A: History
Attachment B: Map