To: Honorable Mayor and Members of Town Council
From: Mark Marlowe, Utilities Director
Matt Benak, Water Resources Manager
Sheri Scott, Water Resources Program Analyst
Title
Update: Plum Creek Diversion Project
Body
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Executive Summary
One of the key pieces of the Town’s long-term water plan is to maximize the use of our local renewable supplies. For this reason, a diversion on Plum Creek has been a part of the long-term water plan since the Plum Creek Water Purification Facility (PCWPF) was first envisioned. Utilities has identified a location for the diversion property owned by the Town of Castle Rock (see Attachment A). A study of options for a diversion on Plum Creek identified an option close to this location as one of the most cost effective and timely. The cost of a diversion on the property owned by the Town is actually more cost effective than the site evaluated in the study as the length of the required pipeline is shorter. The site owned by the Town has other advantages which make it the most cost effective and timely option over all the other options studied to date.
The other advantages of this diversion location include:
1. The Town owns the property which negates the need for any negotiations with third parties.
2. This location decreases the distance downstream from the Plum Creek Water Reclamation Authority (PCWRA) outfall which minimizes stream losses. (In other words we keep more of our water.)
3. The location still allows the potential for partnerships with Castle Pines Metropolitan District (CPMD) and Castle Pines North (CPN).
4. The location results in the shortest pipeline for all of the options and the lowest pumping energy meaning lower long term operational costs.
5. This option results in the need to get easements from only one property owner.
6. Development of the diversion on this property will help move forward utilizing the remaining property at the site for open space and recreation.
Next steps include annexing the property into the Town, and zoning the property under public open space one zoning. The property is a 65-acre parcel was dedicated to the Town for parks, recreation and open space. The diversion will be designed to be installed as ancillary facilities on less than one-acre of the property.
Concurrently with developing the annexation and zoning, Utilities has hired a permitting expert to develop the permitting strategy and conceptual design for the diversion portion of the project at a cost of $36,804. Also concurrently, Utilities has issued a request for proposals to do full design of the pump station and two mile raw water pipeline. The proposals were received on July 24, 2015 for staff evaluation. The cost for design from the low bid is $229,588.
The two mile raw water pipeline connecting the diversion structure along East Plum Creek and to the Town’s existing raw water pipeline on the north side of Town will cross property owned by one landowner. The selected design consultant will identify temporary and permanent easement acquisitions necessary. The Town plans to work with an independent consultant to assist the Town in good-faith negotiations with the property owner to acquire the necessary easements. To meet the overall project schedule, the pipeline will be bid in the spring of 2016 and constructed by 2017.
The benefits of the diversion structure to be located on property owned by the Town are:
• The diversion will give the Town the ability to capture East Plum Creek water rights, our treated effluent flows and our lawn irrigation return flows. This will account for up to 50% (7,635 AF out of 15,400 AF of demand) of our projected water demand in the long-term based on current projections.
• Of the options analyzed in the Alternatives Analysis and Conceptual Design report by CDM Smith, an alternative very close to this location scored the second highest in geographic location; ability to capture and deliver wet water; constructability; time to implement and cost.
• With this option, the Town will not have to purchase or find property on which to construct the diversion.
• This location will give the Town potential partners in the development of the diversion infrastructure to provide increased economies of scale and reduce the needed capital investment.
• This location results in a significantly shorter pipeline from the diversion and subsequently a lower cost for the pipeline and pump station from the diversion back to the existing raw water pipeline.
One disadvantage of this location is that this diversion will not provide the ability to directly capture and transmit our West Plum Creek water rights at a single point. These water rights account for between 25 and 330 acre-feet (AF) annually depending on the stream conditions (drought versus average year). If the Town were to develop a separate, new alluvial well field and pipeline to transmit this water, this would need to be a separate project costing the Town on the order of $9.7 million (based on six new alluvial wells and an 8-inch, 4 mile pipeline). This work could be done later to spread out the costs of the project and still capture most of the available water. It is also important to note that under some conditions the Town will be able to capture these water rights through an exchange, and the Town has a Water Court case in progress to ensure this capability.
It is important to note that the construction of this diversion is just the first part of the project. A pump station, pipeline, and potential upgrades to our PCWPF will also be required. The current cost estimate for the total infrastructure is $25.5 million.
Budget Impact
The appropriation account that will be used to fund this project is 211-4375-443.77-54 (Plum Creek Diversion Project). The project is budgeted in 2015, 2016 and 2017. Castle Pines Metropolitan District (CPMD) and Castle Pines North (CPN) have shown interest in being partners in the diversion infrastructure which could result in economies of scale reducing overall project costs. Final budget impacts will be better defined once the project is designed, allowing for a more comprehensive engineering cost estimate.
Staff Recommendation
Staff recommends annexing the property owned by the Town and zoning the property under public open space one. In addition, staffs recommends continuing with the design and permitting of the diversion, pump station and pipeline concurrently. Part of the goal of the design will be to identify easements required for the pipeline and requiring those easements from the one property owner.
Attachments
Attachment A: Location Map