To: Members of the Castle Rock Water Commission
From: Mark Marlowe, P.E., Director of Castle Rock Water
Lauren Moore, Water Resources Manager
Adriana Alfaro, Water Resources Program Analyst
Title
Resolution Approving a Second Amendment to the Services Agreement with W.W. Wheeler & Associates for Phase 2 of the Quantification of East Plum Creek and Cherry Creek Basin Lawn Irrigation Return Flows [Various sites throughout Town]
Town Council Agenda Date: December 16, 2025 DRAFT
Body
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Executive Summary
Castle Rock Water (CRW) is seeking approval of a Resolution (Attachment A) for the Second Amendment to the Services Agreement (Exhibit 1) with W.W. Wheeler & Associates (Wheeler) for Phase 2 of the quantification of East Plum Creek and Cherry Creek Basin Lawn Irrigation Return Flows (LIRFs). The term of the current agreement is through March 31, 2025 and this amendment request is strictly a time extension of the Services Agreement through December 31, 2026. LIRF quantification is part of CRW’s long-term Water Resources Strategic Master Plan (WRSMP) and includes reuse of both non-renewable groundwater and reusable renewable water supplies. LIRFs are expected to represent approximately 750 acre-feet of water supply on an annual long-term basis which is 5% of the total long-term water supply. LIRFs are a source of augmentation water for the Town’s alluvial wells when pumped out-of-priority.
The scope of work includes a continuation of Phase 1 monitoring of water levels in 28 wells, data collection, and modeling as well as oversight of the construction of 5 additional monitoring wells, the associated well permitting, filing water court applications, and a conceptualized plan for Phase 3.
History of Past Town Council, Boards & Commissions, and Other Discussions
On March 7, 2019, the Town Manager approved the Phase 1 Services Agreement with Wheeler for the 2019 Town of Castle Rock LIRF Quantification Project.
On October 26, 2022, CRW Commission recommended Town Council approval of the Phase 2 LIRF Quantification Project.
On March 11, 2024, Town Council approved the First Amendment which extended the completion date of the original agreement to March 31, 2025.
Discussion
CRW has identified LIRFs as a significant contributor (approximately 5%) to the Town’s long-term water supply as a source of augmentation water for the Town’s alluvial wells when pumped out-of-priority. While the Town is currently claiming LIRFs for two of the five geologically defined zones (totaling approximately 90 AF per year), CRW will need to quantify the volume and timing of return flows in the remaining zones (3, 4, & 5) to fully claim the remainder of these rights (totaling approximately 750 AF per year). A map of the five LIRF zones is shown in Figure 1 below. As part of Phase 1, which was completed in late 2021, 25 monitoring wells were constructed to supplement three existing monitoring wells, and transducers were deployed in all of the wells in order to begin the collection of continuous water level data as required for quantification. Additionally, stream flow monitoring locations were selected and field sampling was conducted monthly. Phase 2 continues forward with the work completed in Phase 1.
Figure 1. Town of Castle Rock LIRF Zones 1 through 5 in the East Plum Creek and Cherry Creek Basin.
Phase 2 includes continuation of the monitoring program established in Phase 1, the completion of five additional monitoring wells in Red Hawk and Sapphire Point neighborhoods (Attachment B), modeling of the timing and quantity of these return flows in both the Plum Creek and Cherry Creek basins, as well as completing and submitting water court applications for the LIRF water rights in both basins. Phase 3 will see the water court applications through their entirety in water court for approval. Once approved in Water Court, the LIRFs will be able to be diverted in East Plum Creek and Cherry Creek at any of our diversion points.
To date the 5 additional monitoring wells have been constructed for a total of 33 monitoring wells that are continuously collecting data. Phase 2 is wrapping up as the engineers are preparing their final reports for the water court applications. Staff anticipate the water court application to be submitted for East Plum Creek by December 2025 with the Cherry Creek LIRF engineering reports and application anticipated shortly after in 2026.
Budget
The total scope of this agreement is not to exceed $336,000. Work on Phase 2 began in November 2022 and will continue through December 2026 at which time it is anticipated Phase 3 will begin. Phase 3 is expected to take 3 years.
Through October 2025, $278,924.83 has been spent of the $336,000 budget. No additional budget is requested with this amendment.
|
Project Account |
Contract Amount |
Contingency |
Total Authorization |
|
211-4340-443.30-70 (Other Professional Services) |
$336,000 |
$16,800 |
$352,800 |
The cost for Phase 1 was $228,497. Phase 3 is expected to cost on the order of $250,000. The total engineering cost to quantify these water rights is estimated to be $831,297. There will be additional legal costs estimated at $XXXX. When comparing this cost to the number of acre-feet available, this is an excellent value of $870 per acre-foot.
Recommendations
Staff recommends Council approval of a Second Amendment to the Services Agreement with W.W. Wheeler & Associates for Phase 2 of the Quantification of East Plum Creek and Cherry Creek Basin Lawn Irrigation Return Flows (LIRFs).
Proposed Motion
“I move to recommend to Town Council approval of the Resolution as presented”
Attachments
Attachment A: Resolution (Not Attached)
Exhibit 1: Agreement (Not Attached)
Attachment B: Location Map