SIERRA VISTA — Rainwater falling on impervious surfaces, like streets and parking lots, is an as-yet-untapped resource in Sierra Vista, but soon some of that water will become a benefit for the San Pedro River and the aquifer which sustains it.
Karen Riggs with Cochise Conservation and Recharge Network (CCRN), and Ricardo Aguirre, founder of Holistic Engineering and Land Management, Inc., provided an update on the progress of the recharge project to interested citizens during a July 1 meeting.
For the past three years, CCRN, a consortium of the county, Sierra Vista, Bisbee, The Nature Conservancy (TNC), Upper San Pedro Partnership and the Natural Resource Conservation Service, has been actively looking for ways to help sustain the riverine ecosystem and the aquifer, Riggs said.
The Coyote Wash Urban Enhanced Runoff Recharge Project is located on a 2,984–acre parcel which is an active ranch in the Buena subwatershed under a conservation easement held by TNC and owned by Cochise County, Riggs said.
TNC estimates the easement conserves 238–acre feet a year of groundwater that will not be pumped due to precluded development. This acreage also buffers the south border of Fort Huachuca’s east range from additional development.
County staff and consultants have been studying Coyote Wash to find the most advantageous and economically feasible locations for recharge projects and one in particular is the focus of interest, the gravel pit.
The Bella Vista/Coyote Wash recharge project is expected to take stormwater runoff, also known as urban enhanced runoff, from paved surfaces and channel it through a series of retention basins which are meant to slow the water down, catch sediment, provide some infiltration recharge and still allow some runoff to reach the river. The project could provide anywhere from 150 to 600 acre-feet a year depending on the amount of rainfall, said Riggs.
The project goal is to “raise groundwater levels in a critical area that both supports river base flows and protects the river from municipal groundwater pumping centers,” she noted. Monitoring various sites within the Bella Vista parcel began in 2016 which helped define the area where the recharge would be most cost effective.
“We did an economic analysis and found we needed the project to recharge at least 150 acre-feet a year to be feasible,” she said. “Predevelopment runoff will continue to run downstream.”
The first project will be located in the gravel pit area in Coyote Wash which has a sandy bottom, Aguirre said. Dry wells and infiltration galleries will be in the design. No impoundment will be higher than six feet to stay under the definition of a dam.
The project will have to go before the Army Corps of Engineers as it pertains to the Clean Water Act, he added.
Holly Richter, TNC hydrologist, noted Coyote Wash actually receives “several hundred acre-feet” of rainwater every year and the amount the project will deflect and slow will not hinder the flow reaching the river.
“We had to have at least 150 acre-feet to make the project beneficial,” she said. “It will create a floodplain similar to what it looked like pre-development.”
Two other locations in the wash for recharge were also identified further east.
The monitoring data will be available for public view later this month, Riggs said. The draft EA will be available to the public sometime this fall.
Public comments will be accepted through Monday, July 15.
Cochise County applied for and was awarded two grants totaling $550,000 to develop a watershed plan and conduct an Environmental Assessment, which are underway, Aguirre continued. The next step will be the design of the recharge facilities.
Currently, there are three locations farther south in Palominas where projects have been constructed — Horseshoe Draw Sediment Control and Recharge, Palominas Recharge and Three Canyons Recharge facilities. Two other properties, one along the Babocomari River to the west and one south of Coyote Wash called Riverstone may provide additional recharge facilities.
For more information, visit the CCRN website: https://ccrnsanpedro.org/.