A conversation with Mark Marlowe Director of Castle Rock Water for the Town of Castle Rock, CO


Mark Marlowe has been the Director of Castle Rock Water for the Town of Castle Rock, Colorado since 2013. The Town of Castle Rock is located in the South Denver Metro Area and provides drinking water, wastewater, and stormwater services to a growing community of 70,000 residents. Mark has spent his career of more than 20 years in the environmental and water utilities industries, and prior to joining Castle Rock Water, he worked in utility management in Georgia. Under Mark’s leadership, Castle Rock has implemented forward-thinking strategies to build resiliency into its water supply portfolio and to use water as efficiently as possible, including reusing water supplies and a water budget-based rate structure.

WaterNow Alliance caught up with Mark this month to discuss Castle Rock Water’s water efficiency and alternative supply programs and to talk about where the town will go next to meet the community’s water demands.


You began your career in utility management in Georgia. Would you say that the water challenges communities are facing in Georgia are similar or different from those faced here in Colorado?

Many of the challenges are really the same. We continue to learn more and more about water quality and water providers are having to make water treatment adjustments in response to that information. The other thing that’s similar is water infrastructure. It’s very expensive to maintain water infrastructure over the long-term no matter where you are, and that’s compounded by the fact that water itself is still very inexpensive. I think rates and fees for water will be rising in Colorado and in Georgia.

Both places also deal with drought conditions. Georgia typically has more renewable, surface water supplies, but they’re still implementing progressive strategies like graywater reuse to manage supply challenges. I’d say the biggest differences between the two is that in Colorado’s Front  Range – where Castle Rock is located - water is typically scarcer, and Colorado’s water rights system adds a significant amount of complexity to everything you do relative to water supply and how that supply is used.


Where does Castle Rock receive its water supply from, and what are the major water supply challenges facing the town?

Last year, Castle Rock Water received about 70 percent of our supply from the Denver Basin aquifers and 30 percent from renewable water sources. Our renewable water supply comes from surface water from East Plum Creek, Cherry Creek, and from the WISE Authority, a water sharing agreement between 10 South Metro Water Suppliers, Denver Water and Aurora Water that allows us to access both mountain water supplies in the South Platte River and reuse water. One of the main challenges facing the town is that renewable water rights are limited in the Front Range at this point, and we’re a little bit late to the game. The cost of purchasing new water rights is high, and those water rights aren’t close by, so they would require purchasing or constructing expensive conveyance infrastructure.

The issue with groundwater is that the Denver Basin Aquifers are being drawn down and water levels are expected to continue to drop over the next 50 years. This creates a couple of challenges for the Town. First, the groundwater is more difficult and expensive to recover, and second, in the long run the town may not be able to rely upon the aquifer for our water needs. In the longer term, we’d like to begin storing water in the aquifer in wet years where there’s surplus surface water supply to try to balance out the aquifer and to have an extra storage reservoir available for when we need to access drought supplies. We’ve already converted several wells to be able to store and recover water in the aquifer.

Castle Rock’s goal is to move away from our reliance on non-renewable groundwater, and ultimately to achieve 75% or more renewable water supply by 2050 to ensure a sustainable water supply.


Between 2010 and 2018, Castle Rock reduced its gallons per capita per day (GPCD) by 19%, from approximately 132 to 108. What solutions did Castle Rock implement to achieve that per capita demand reduction?

Reducing our GPCD is one of the things we’re really focused on in terms of next steps in water efficiency and conservation in Castle Rock. We updated our Water Efficiency Plan in 2016 and our new goal is to get per capita demand down to around 100 GPCD. We’re doing a ton of work on water efficiency in order to accomplish this goal. One of our key successful strategies is our water budget-based rate structure that’s designed to encourage and incentivize households to use less water. This provides individual water budgets for each account based on indoor water use and outdoor irrigable area, and higher rates are charged for water use beyond the budget of each account. Next year, we’ll be taking this a step further by basing the water budgets for commercial and HOA customers off of the type of landscape they have installed and not just their irrigable area. This will essentially reduce their outdoor water budget, meaning they’ll have to manage their water use more efficiently. In the long term, this is where we're heading for the entire customer base.

We also have programs in place to encourage water efficient, new development in which developers can pay a significantly reduced system development fee if they develop projects with more efficient technologies and approaches. Our landscape ordinance was also developed to encourage efficiency. Since 2004, all of our commercial and HOA accounts have been required to put in hybrid grasses or native grasses instead of high water use Kentucky Bluegrass, and now all new residential customers are required to do the same.


Castle Rock is one of the seven fastest growing cities in America, according to recent U.S. Census Data (May 2017), and is expected to reach 100,000 people by 2060. What additional strategies is the Town considering in order to continue to develop sustainably and meet the water supply needs of your community?

There are a number of important strategies we’re looking at. One of the interesting things that we’re doing as a part of our water reuse program is exploring direct potable reuse. This would allow us to more efficiently use our reuse water by directly bringing that water back from the water reclamation facility to our drinking water treatment plan, as opposed to putting it back into the creek and letting it flow downstream and then taking it out and treating it. Direct potable reuse would be more efficient from a cost perspective, and it also ensures that we don’t lose any of that water right to infiltration or evaporation. This is part of our long-term plan, and we’re part of a group of utilities and organizations working on a report right now that’s looking at direct reuse regulatory requirements for the State of Colorado.

We’re also continuing to look for new ways to incentivize and require more efficient development. For example, we’re looking at encouraging more efficient toilets and tools like leak detection devices on customers’ service lines so they can access water use data from their smartphones.

We’ll also be working on how to make our existing outdoor landscapes as efficient as possible by transitioning the look and feel of the whole community to what we call “ColoradoScape”, which is the idea of using native plants to create efficient, drought-tolerant landscapes. And we'll continue to work with the Parks Department on limiting turf in Castle Rock’s parks. For example, last year we helped fund the conversion of baseball fields from Kentucky bluegrass to synthetic turf, and that’s had a huge impact on reducing water demand and allowing the baseball fields to be utilized for more of the year.


Castle Rock has been in the news lately for being one of the only cities in Colorado to develop infrastructure to reuse treated wastewater as part of your water supply. What was the impetus behind this decision, and how have community members responded?

As we’ve discussed, Castle Rock has limited water supply options so the main impetus behind the reuse project is necessity. Castle Rock needs to implement our sustainable, long-term renewable water plan that will allow us to be less reliant on the Denver Basin aquifers. Castle Rock actually made the decision to reuse treated wastewater back in 2005 for indirect potable reuse and non-potable supplies. Since then, the Town has been reaching out to the community to talk about this and receive community input. Right now we’re in the middle of constructing upgrades to our surface water treatment plant that will be designed to treat a reusable water supply. The way this will work is the wastewater will be treated at our water reclamation facility and then it’ll go back in East Plum Creek and flow six or so miles downstream. Next, our diversion structure will pull that water back out once it’s blended with the Plum Creek water. We’re now in the process of finishing construction on a pump station and pipeline that will bring the water back to the treatment plant. Theses supplies will come online in Fall 2020.

We’ve done a lot of outreach around this project, and we’ve been very transparent with the community to make sure they’re fully educated on this. For the most part, the community has been very supportive of this project, they understand that it’s a reliable water supply that we can count on and that it’s one of the most efficient, cost-effective water supplies we can access because we already have the water rights and it’s close to home.


This year, Castle Rock became the 3rd municipality or county in Colorado to pass an ordinance allowing developers to install graywater systems in new homes. What were the goals of this ordinance and how would you measure success in 5 years?

The goal of the graywater ordinance is to improve the water efficiency of future, new residential homes in Castle Rock. There are limited opportunities for improving indoor water efficiency, and this is one of those opportunities, so we wanted to provide this as an option for home builders and developers in Castle Rock. To encourage graywater use, we’ve added graywater systems to our incentive structure for water efficient new development.

The goal right now for Castle Rock is to work with the homebuilders and the providers of these systems to get a pilot project moving forward where we can actually get a better idea of how this is going to work. In my mind, success five years from now would be that we have figured out graywater systems that allow new homes to use water more efficiently.


Why do you think that sustainable water management in Castle Rock and throughout the Front Range is so important?

You know, it's really for the same reason that it's important everywhere- sustainable water is the fundamental basis for society as we know it. It's perhaps the most important infrastructure and resource for public health beyond literally anything else.

In Castle Rock and the Front Range it’s even more important for a number of critical reasons. The region is growing at an extremely fast pace and the water resources here are limited. There are also a lot of unknowns with respect to how our water availability will change over time due to climate change. So we really have to be thoughtful in terms of making sure that we develop systems now that are going to be sustainable to support that growth here in Colorado.

We’re lucky here in Castle Rock to have council members and customers that are very supportive of using water as efficiently as possible.  They have a strong understanding of how precious and important our water resources are, and Castle Rock Water has a lot of community support to do what we need to do to make sure we’re sustainably managing the resource, so that’s pretty exciting!

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