Purple Pipes in Cavelle Mesa: Recycled Water for the Parks

The pipes under Orrin Park in Cavelle Mesa are purple. Nobody sees them, but the color matters. Purple is the standard marking for recycled water in the United States, and it warns every crew that digs there that the pipe below is not drinking water.

Cavelle Mesa is a dry place. The city sits on the edge of a desert basin, and for most of its history it bought all of its water from a district many miles away. Fifteen years ago the council approved a second water system, one that carries treated wastewater to places that do not need drinking water at all.

The recycled water starts where all the city's wastewater does, at the reclamation plant east of the highway. There it goes through the usual stages: screening, settling, biological treatment, and disinfection. Then it goes further. Filters and a second round of disinfection bring it to the standard the state sets for irrigation and industrial use. From there it enters its own pipe network, marked in purple, with its own pumps and its own storage tank.

That water now irrigates the parks, the ball fields, the cemetery, and the planted strips down the middle of the main roads. It cools two industrial buildings. It fills the tanker trucks that damp down dust at construction sites. None of it reaches a kitchen tap, and by state rule none of it may.

Keeping the two systems separate is a full-time job. A cross-connection is any point where a recycled water line could touch a drinking water line, and preventing cross-connections is the whole purpose of the program's inspection staff. Before any site can be switched to purple pipe, crews run a shutdown test. They close the drinking water supply to the property, open the recycled line, and check every fixture in the building. If a single tap still runs, there is a connection somewhere that nobody documented, and the site does not go into service until it is found and cut.

The signs are part of the system too. Purple tags hang on the valves, and purple placards stand at the edge of every irrigated field. The city's rule is that a resident should be able to tell what is in a pipe without asking anyone.

Not everyone is satisfied. At a council meeting last spring, a resident named Halbert Nance said what a number of his neighbors think. He argued that the city spent years of budget on a second pipe network for grass while household bills went up, and that a city short of water should ask people to plant less lawn instead of building a system to water more of it. He also said he did not trust that the two networks would stay separate forever.

The city's answers are on the record. Recycled water now supplies about a fifth of everything Cavelle Mesa uses, which is water the city no longer has to buy from the district. The second network cost a great deal, but the city argues that it costs less than the next new supply would. On the separation question, the utility points to the shutdown tests and to a public log of every inspection.

The debate in Cavelle Mesa is small compared with what other places are attempting. In Orange County, California, a system called the Groundwater Replenishment System treats wastewater to drinking water standards and returns it to the aquifer that the county's wells draw from. At 130 million gallons per day, it is the largest indirect potable reuse facility in the world. Cavelle Mesa does nothing of the kind. Its purple pipes stop at the edge of the ball field.

Still, the two projects raise the same question, and it is not really an engineering question. The engineering is settled and the monitoring is public. What is unsettled is how much a community trusts the people who run its water, and that trust depends on whether the testing is consistent and the records are open to anyone who asks.

1. What does the color purple indicate about a pipe, and why does the marking matter to work crews?
2. According to the passage, what does Cavelle Mesa use its recycled water for, and what may it never be used for?
3. Explain the shutdown test in your own words, and state what result would stop a site from going into service.
4. The passage says the debate in Cavelle Mesa is "not really an engineering question." Using details from the passage, explain what the writer means.
5. How does the Orange County system described near the end differ from what Cavelle Mesa does?
6. Halbert Nance argues that a city short of water should ask residents to plant less lawn instead of building a system to water more of it. Write a claim that answers his argument, and support it with two details from the passage.
7. Write a short informative paragraph explaining the two-pipe system to a reader who has never seen one. Include what the second system carries, where the water goes, and one rule that keeps the systems apart.