To: Members of the Castle Rock Water Commission
From: Mark Marlowe, P.E., Director of Castle Rock Water
Mark Henderson, P.E., Assistant Director of Castle Rock Water
Lauren Moore, Water Resources Project Manager
Title
Resolution Approving an Agreement between the Town of Castle Rock, Castle Pines Metropolitan District, Castle Pines North Metropolitan District, Highlands Ranch Water and Sanitation District, and Dominion Water and Sanitation District, for the Plum Creek Stream Gage [Northwest Douglas County, Colorado]
Town Council Agenda Date: September 2, 2025
Body
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Executive Summary
Castle Rock Water is seeking Town Council approval of a Resolution (Attachment A) for an Agreement Regarding Plum Creek Stream Gage (Agreement) (see Exhibit 1) between Castle Pines Metropolitan District, Castle Pines North Metropolitan District, Highlands Ranch Water and Sanitation District, Dominion Water and Sanitation District, and the Town of Castle Rock. The purpose of this agreement is to collaborate and cost share as needed with nearby entities that have water rights and/or reuse flows in Plum Creek to maintain a functioning stream flow measuring device in order to capture their respective water rights.
Key aspects of the Agreement include:
• Gage ownership based on pro rata share of average daily Plum Creek use
• Cost share for ongoing gage operation and maintenance;
• Cost share for stream channel restoration and on-going maintenance;
• Establishes an operating committee for allocating responsibilities and approving budget; and
• Outlines emergency operation and maintenance procedures.
Discussion
In an effort to maximize the Town’s reusable return flows as well as the water rights of other downstream users of Plum Creek, the Division of Water Resources (DWR) installed a cantilever radar measuring instrument and developed a stage/discharge rating curve to measure streamflow in Plum Creek upstream of Chatfield Reservoir. Prior to the use of this DWR gage, a United States Geological Survey (USGS) gage approximately 1 mile upstream known as the Titan Road Gage has been the approved, and in some cases, decreed location for determination of available streamflow for diversions at Chatfield Reservoir. For years, this stream section has proven difficult for measurement, particularly in times of low flows. A few years ago, the DWR installed an additional stream gage for better accuracy, now called the Plum Creek Gage Above Chatfield Reservoir (PLUCHACO). The location where the PLUCHACO gage is located has experienced excessive sanding and has recently been disabled indefinitely. In order to get this stream gage functional again, stream channel restoration and gage maintenance must be completed and this Agreement is the first step in the process.
In support of ongoing streamflow monitoring and administration, this Agreement between several water users, including the Town, incorporates provisions for stream channel restoration, ongoing operations and maintenance, as well as a cost-share component. The Agreement will be one of five licenses and/or agreements necessary for the gage to be formally used in water administration. The other remaining agreements will include a license with the U.S. Army Corps of Engineers (USACE), an agreement with Colorado Parks and Wildlife (CPW), an administrative agreement with the Division of Water Resources (DWR), and a contract with a stream channel restorationist to complete stream restoration. Ensuring all agreements are in place is critical for maintaining the ability to claim water rights at the gage, especially during low flows.
Budget Impact
The Agreement Regarding Plum Creek Gage does not directly impact the Water Resources budget but rather establishes the Town’s 50% pro rata share in any needed gage or stream channel restoration and ongoing maintenance.
Staff Recommendation
Staff recommends Town Council approve the Plum Creek Gage IGA.
Proposed Motion
“I move to approve the Resolution as introduced by title.”
Alternative Motions
“I move to approve the resolution as introduced by title, with the following conditions: (list conditions).
“I move to continue this item to the Town Council meeting on _____ date to allow additional time to (list information needed).”
Attachments
Attachment A: Resolution (Not Attached)
Exhibit 1: Agreement - DRAFT