To: Honorable Mayor and Members of Town Council
Through: David L. Corliss, Town Manager
From: Mark Marlowe, P.E., Director of Castle Rock Water
Matt Benak, P.E., Water Resources Manager
Title
Resolution Approving an Intergovernmental Agreement for Rueter-Hess Drought Water Supply Pilot Plan between the Town of Castle, Denver Water, Parker Water and Sanitation District, and East Cherry Creek Valley Water and Sanitation District
Body
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Executive Summary
The purpose of this memorandum is to request Town Council approval of an Intergovernmental Agreement (IGA) with Denver Water, Parker Water and Sanitation District (PWSD) and East Cherry Creek Valley Water and Sanitation District for the Rueter-Hess Drought Water Supply Pilot Plan. The resolution approving the agreement is provided in Attachment A and the Intergovernmental Agreement (IGA) is Exhibit 1 to the Resolution.
The aforementioned parties are proposing a short-term Pilot Plan that involves storage of water in Rueter-Hess Reservoir (RHR) under the current terms of the Rueter-Hess Reservoir (RHR) 404 permit. This pilot will facilitate Castle Rock storing its currently permitted fully-reusable return flows, which are captured and stored in Chatfield Reservoir, into RHR using existing infrastructure.
The way the pilot would operate is that Denver Water would transfer “Pilot Water” into the WISE System using the existing Conduit 111 / WISE Pipeline interconnection. Pilot Water will be pumped through WISE infrastructure to PWSD’s Rueter-Hess Water Purification Facility (RHWPF) where it combines with other water and enters PWSD’s potable water distribution system. When PWSD uses the Pilot Water in the manner described above, PWSD has a reduced need to withdraw water supplies stored in RHR. Therefore, PWSD will book over water stored in a PWSD RHR storage account into a new PWSD subaccount titled “Pilot Plan Storage Account.”
Denver Water will coordinate with Castle Rock Water to identify a mutually agreeable time for Castle Rock Water to transfer water in its Chatfield Reservoir storage account to a Denver Water Chatfield Reservoir storage account for water being transferred from the RHR Pilot Plan Storage Account to the Castle Rock Water RHR storage account. Denver Water will receive all of the water delivered to PWSD, less any losses incurred under the Pilot Plan program.
The benefit of this agreement to Castle Rock is that it gives an opportunity to add additional supplies into RHR, where through other agreements with PWSD, we can treat and deliver additional potable water to our customers. PWSD will realize higher water levels in RHR and Denver Water will be able investigate potential future options for storing water in RHR. The pilot project will also use some of ECCV’s pumping and piping infrastructure to move water to PWSD’s system, and because the primary benefit is for Castle Rock, the Town will pay energy recovery costs and administrative fees to ECCV during the pilot project.
History of Past Town Council, Boards & Commissions, or Other Discussions
On August 18, 2020, the Castle Rock Water Commission unanimously recommended that Town Council approve the IGA when its final form is presented for Council consideration.
Discussion
Rueter-Hess Reservoir is located in northeastern Douglas County one mile east of Castle Pines Parkway and I-25 on property owned by PWSD. RHR was completed in 2012 and, when filled, will have a capacity of 75,000 acre feet (AF) of water and encompass 1,170 acres. Along with PWSD, Castle Pines North and Stonegate, Castle Rock is also a participant in the reservoir and owns 8,000 AF of storage space.
To date, the Town has only been able to store around 1% of its current allocated space in water. The water we have been able to store is made up of return flows from the Town that are treated at the Pinery’s wastewater treatment facility and discharged into Cherry Creek. The Town has an existing agreement with PWSD to capture these return flows and pump them into RHR, however, PWSD is limited by their water rights on Cherry Creek of when they can pump, thus limiting what the Town is able to put into RHR.
As the Chatfield Reservoir Reallocation Project was nearing completion, Castle Rock was approached by Denver Water and PWSD in late 2019 with the idea of a reservoir exchange pilot project. The basic concept was to have PWSD use some of Denver Water’s fully reusable supplies within their distribution system, keep a like amount of water within RHR (that they otherwise would have had to draw upon), and then, at a mutually agreeable time, and for a mutually agreeable volume, a reservoir trade would be made with Denver Water and Castle Rock Water. Castle Rock would trade a volume of its fully reusable supplies stored in Chatfield to Denver Water, and Denver Water would trade the same volume of water over to Castle Rock in RHR.
The concept of the Pilot Project has been discussed with both the Colorado Division of Water Resources (see response letter Attachment B) and the U.S. Army Corps of Engineers who are both in agreement that the Pilot Project may proceed without injury or in violation of existing permits. The parties also provided additional information to the Colorado Division of Water Resources (Attachment C) in an October 9, 2020 letter.
The Pilot Project is expected to last no more than 48 months from the date all Parties sign the IGA. The exact amount of Pilot Water to be transferred into and out of the Pilot Plan Storage Account is not precisely known, but the objective of the Pilot Plan is to test relatively small amounts of water transfers (e.g. 100 to 200 AF per transfer). Likely between 500 and 1,000 acre-feet of water will be transferred into and out of RHR over the entire Pilot Plan duration.
Budget Impact
The cost of the Pilot Project will depend on the total quantity of water transferred and during the time of year (ECCV’s summer pumping rates are higher than the winter pumping rates). Assuming summer pumping and $400 monthly administrative costs during the months when water is pumped, we estimate the cost of the Pilot Project will be approximately $80,000 over a four-year period. Payments for this Pilot Project will be made from the CIP operation and maintenance account 211-4375-443.40-90 <Project Code WR RHR>.
Staff Recommendation
Staff and Castle Rock Water Commission recommend that Town Council approve the first amendment to the Water Service IGA.
Proposed Motion
“I move to approve the Resolution as introduced by title.”
Attachments
Attachment A: Resolution
Exhibit 1: Intergovernmental Agreement
Attachment B: Letter dated May 8, 2020 from Colorado Division of Water Resources
Attachment C: Letter dated October 9, 2020 from Colorado Division of Water Resources