It makes sense to use what you have available locally before looking for water outside the Town. This is why Castle Rock Water has firmed up existing local water rights in Plum Creek that go back to the 1860s. We also have the opportunity in the near future to reuse the deep groundwater we pump from the Denver Basin aquifer. To use all of these local renewable water resources, we needed a special treatment facility.
Plum Creek Water Purification Facility
The Plum Creek Water Purification Facility is Castle Rock Water’s crowning jewel and one of the largest pieces in the Town’s renewable water puzzle completed to date. The facility, along with our first access points to renewable surface water in Plum Creek, was completed in 2013, at a total investment of about $22.5 million. The facility currently has the capacity to treat all the water the Town needs on a typical winter day, that is up to 4 million gallons of renewable surface water or groundwater per day.
The Town is planning on this increase. The good news for existing residents in the Town is this planned growth will help to spread out and minimize the costs of a renewable water supply. Eventually, the Plum Creek Water Purification Facility will treat renewable surface water almost exclusively, a big part of our renewable water supply.
Developing that supply is the purpose of investing an estimated $24 million to construct the planned raw water diversion on Plum Creek north of the Town. The Plum Creek diversion is one of the big projects that Castle Rock Water will implement by 2017 to utilize existing Plum Creek native water rights and reuse Denver Basin water rights.
The Plum Creek Water Purification Facility captures and treats water of which the Town owns the rights. Further planned improvements at the purification facility will expand capacity to 12 million gallons a day. These expansions are projected to take place over the course of the next several decades as needed to reach our long-term goal.
So far, the Town has essentially transitioned from a mostly nonrenewable water supply to a 10 to 22 percent renewable water from sources such as junior and senior tributary water rights on East and West Plum Creek, reclaimed water released to East Plum Creek and lawn irrigation flows. In the future, this facility will also treat imported surface water.
As part of the Plum Creek Water Purification Facility project, six new alluvial wells were constructed along East Plum Creek. These wells supplement the Town's three existing alluvial wells by supplying renewable water for treatment.
The creek alluvium consists of sand layers that have been deposited by the stream channel over many years. Water is naturally stored in the pore spaces between the sand grains underground. These wells have been completed 50- to 60-feet deep in the saturated alluvium, tapping the subsurface aquifer that is then replenished by natural flows in East Plum Creek. Because the source of water is from surface runoff flowing into the creek, this water supply is considered renewable.
The nine alluvial wells provide anywhere from 10 to 20 percent of the Town's water supply needs depending on overall system demands. Water from these alluvial wells is also processed through the Plum Creek Water Purification Facility. The amount of water produced by the alluvial wells depends on a number of factors, including the efficiency of the wells, the amount of stream flows available for recharging the aquifer, and the priority of Town's surface water rights. Approximately 658 million gallons of renewable water have been treated at the plant since its opening.
The Central Well Field consists of seven alluvial wells located in The Meadows development near East Plum Creek. As part of the Plum Creek Water Purification Facility project, seven well sites were identified for construction in two areas of the Central Well Field. The northern cluster of four wells near Atrium Drive were constructed in 2013 and 2014. The Plum Creek Alluvial Well Field Project is to construct the three remaining alluvial wells in the Central Well Field. These additional three wells, near the Meadows Parkway bridge, have been deemed necessary due to a projected water supply shortfall in summer 2016 as a result of increased population growth.
Alluvial wells are simply defined as wells constructed in the alluvium deposits of a stream (see diagram below). Since the water source for the alluvial wells is an alluvial aquifer recharged, in this case by East Plum Creek, the wells are classified as a renewable water source. Construction of these three alluvial wells began in December 2015 and will take approximately six months to complete.
A need for a sustainable long-term water supply was identified in the Town’s Water Resources Strategic Master Plan. One of the major goals of that plan is to establish renewable, sustainable water supplies that account for 75 percent of the annual demand for water in Castle Rock by 2050.