A HOLDING POND at the Sedona Wastewater Treatment Plant.

by Cyndy Hardy

SEDONA, AZ – July 9, 2008 – The Sedona City Council voted 6-1 Tuesday to move forward with seeking permits to dispose treated effluent in the future via aquifer recharge.

Mayor Rob Adams voted against the motion, which included acceptance of an approximately $210,000 report prepared by Burgess & Niple Inc, a Tempe engineering firm; and approval to issue a request for proposals for a project consultant.

A brief history

The gap between the volume of waste inflow and the city’s ability to dispose the treated effluent has been a concern in Sedona for at least 12 years, according to City Manager Eric Levitt.

Sedona residents, businesses and tourists currently flush about 1.2 million gallons of wastewater into the city sewer system every day.

The waste is treated at the Sedona Wastewater Treatment Plant; and the effluent product is disposed according to state and federal rules.

The Arizona Department of Environmental Quality (ADEQ) currently does not allow the city to dispose its treated effluent off-site. So, the city disposes effluent by spraying some over about 282 acres of open fields; some evaporates in holding ponds; and some is infiltrated into about 27 acres of man-made wetlands.

The amount of effluent disposed varies according to how well the environment can soak it up. In winter months and during rainy seasons, the ground can’t accept as much water as during hot arid weather, so the excess is stored until conditions are conducive.

The wastewater treatment plant can dispose about 1.6 million gallons per day at the plant’s current maximum capacity. At the current growth rate, waste inflow will exceed the plant’s capacity in about five years.

Officials project that inflow will increase to about 2.6 million gallons per day by build out, excluding land not already on the radar to be added to the sewer system.

The treated water has to go somewhere.

Options studied by Burgess & Niple

Increasing the city’s treatment plant capacity won’t solve the problem, according to James Campbell, Phoenix district director for Burgess & Niple.

The city would need to increase its wetlands by at least 500 acres and be prepared to maintain those wetlands for the new riparian plants and animals sure to move in, he said.

The U.S. Forest Service won’t allow any new riparian development on its land; meaning it could be difficult for the city to find land to expand.

Mr. Campbell advised the city to give up on point source discharge as a viable option, based on his discussions with the Arizona Department of Water Resources and the Arizona Department of Environmental Quality.

Sedona’s treated water rates a ‘B’ by ADEQ standards, although it could rate a ‘B+’ if the city routinely performed “some tests,” according to a July 8 city staff report.

If Sedona’s effluent were rated ‘A+’ it could theoretically be discharged into a body of water. Locally, that means Oak Creek and the Verde River.

Sedona can’t dump its effluent into Oak Creek because it is a protected water way. ADEQ won’t allow any new or increased load to the creek or any of its tributaries.

Additionally, Burgess & Niple reported that ADEQ probably won’t let the city dump water into nearby washes that drain into the Oak Creek Basin unless the treated water is essentially purer than the natural water of the creek.

Burgess & Niple identified discharge into the Verde River as a possible, if expensive, option. First, the city would have to upgrade its effluent treatment to ‘A+’ quality. Then the city would have to build a 9-mile pipeline to transport the water to the Verde River. The city isn’t sure how much this option might cost, but Sedona Public Works Director Charles Mosley estimated a planning budget of $10 million to $15 million.

Recommended option

SEDONA’S EFFLUENT could be recharged into the Vadose Zone above the underground water table. Source: U.S. Geological Survey