Permit-ready percolation tests and stamped septic designs for Coolidge, Randolph, Valley Farms, and the acreage between them. 48-hour reports from a design-only firm that never bids the install.
Start Your ProjectThe Census Bureau's newest city estimates rank Coolidge as the fastest-growing city in Arizona, up more than 48 percent between July 2020 and July 2025. The 2020 count was 13,218 residents. By mid-2025 the estimate had already passed 19,900. You can trace the payrolls behind that curve on one short drive. Lucid agreed in April 2025 to take over the former Nikola plant at 680 E Houser Rd out of bankruptcy and extended job offers to more than 300 of the people who had worked there. Procter & Gamble has committed 500 million dollars to a planned fabric-care plant on 427 acres at Inland Port Arizona, expected to bring roughly 500 jobs. And SRP won approval in June 2023 to add 575 megawatts at the Coolidge Generating Station.
The sewer map tells a smaller story. The City of Coolidge runs its own wastewater utility: a 2 million-gallon-per-day lagoon treatment plant, about 60 miles of collection lines, more than 1,465 manholes, and 12 lift stations. That network reaches in-town subdivisions such as Carter Ranch, McClellan Meadows, and Picacho Crossing, and it largely stops there. Out-of-city customers who can connect at all pay a 30 percent surcharge on city wastewater rates. Global Water's buildout along SR 87 exists to serve the Inland Port industrial corridor, not rural rooftops. So the unincorporated communities of Randolph, Valley Farms, and La Palma, the horse properties along E Graythorn Way and W Appaloosa Trl, and the one-to-forty-acre splits cut from old San Carlos Project cotton ground all sit past the end of the pipe. The county's own FAQ is blunt about what that means: no sewer connection option, septic permit.
Every one of those permits stands on a soil report, and that report is our entire business. Perc Test AZ runs the site investigation, digs and times the perc holes, and delivers the stamped design your Pinal County application needs, typically within 48 hours of fieldwork. We design only. We never bid installations, so the numbers in your report answer to your dirt and the county reviewer, not to an installer's bid sheet.
The federal soil survey that mapped this valley in 1936, the Casa Grande Area survey of Pinal County, named two soil series that still decide local perc results, and one of them carries this town's name. The Coolidge series is a well-drained sandy loam with moderately rapid permeability and a calcic caliche horizon that can start anywhere from 14 to 40 inches down, running 6 to 25 percent calcium carbonate. Its neighbor, the Casa Grande series, later designated Arizona's representative state soil, behaves nothing like it: a sodium-affected natric horizon holding 18 to 35 percent clay, with permeability the USDA rates slow to very slow.
Which series sits under your stakes often comes down to farming history. Bottoms that grew irrigated cotton under San Carlos Project water trend toward Trix clay loams, strongly calcareous with 25 to 35 percent clay in buried horizons, and toward sodic Casa Grande units where decades of irrigation left tight, dispersed ground. Those parcels tend to test slow, and slow results can push a design from conventional trenches to an alternative system. The sandier Coolidge and Laveen ground percs well by comparison, but caliche is its wildcard. At 14 inches, the cemented layer can sit exactly where a trench bottom wants to be. A lot off E Storey Rd and a lot off N Skousen Rd can give different answers on the same afternoon.
None of that gets settled by a soil map. It gets settled by holes dug at the actual disposal-field location, logged horizon by horizon, with the caliche contact recorded and percolation rates timed against Pinal County's criteria. That is the dataset we hand you. When conventional criteria fail, we design the alternative system that passes.
Percolation tests and full R18-9-A310 site investigations for Coolidge, Randolph, and Valley Farms parcels, with permit-ready reports in your hands within 48 hours of the dig.
Stamped conventional and alternative system designs sized from your perc data and lot layout, formatted for Pinal County Aquifer Protection Division review.
Builders and installers: we test and design only. Your client stays your client, and the installation bid stays yours.
Septic permits around Coolidge are not a city product. They come from the Pinal County Aquifer Protection Division, the county's septic program, which reviews applications at 85 N Florence Street in Florence under authority delegated by the Arizona Department of Environmental Quality. The division permits conventional systems up to 24,000 gallons per day and alternative systems up to 3,000 gallons per day, a range that covers a single home on Valley Farms acreage as easily as a small commercial building. Our Pinal County service page explains how the division operates across the rest of the county.
The technical spine of the application is the site investigation required by Arizona Administrative Code R18-9-A310: a surface and subsurface characterization, performed by a qualified investigator, that documents anything on or under the parcel that could interfere with a disposal system. We build our field reports to that rule section by section, so the reviewer is not writing back for missing data. If you want to see the full sequence before you spend a dollar, from application through final inspection, our step-by-step Pinal County septic permit guide walks the whole process.
City sewer reaches in-town subdivisions like Carter Ranch, McClellan Meadows, and Picacho Crossing. Outside city limits a connection is sometimes possible, but it carries a 30 percent out-of-city surcharge and many parcels have no line within reach at all. If your property has no sewer connection option, Pinal County requires a septic permit.
City code and the county determine whether a connection is required for a specific parcel. We can perc test the lot while you confirm that answer.
Sometimes easily, sometimes not. Acreage irrigated under the San Carlos Project often sits on Trix clay loams or sodic Casa Grande soils, which the USDA rates between moderately slow and very slow, while the sandier Coolidge and Laveen series drain far better.
A slow result does not end the project. It usually means an alternative system design instead of a conventional one, and we produce both.
No. Arizona Administrative Code R18-9-A310 requires a site investigation on the parcel being permitted, with surface and subsurface characterization by a qualified investigator. Soils here change over short distances, and the caliche depth on your lot, not the one next door, controls your trench design.
The percolation data from that investigation sets the absorption rate used to size your disposal field.
Permit-ready reports typically go out within 48 hours of fieldwork, formatted for Pinal County Aquifer Protection Division review.
Design is the only thing we sell, so there is no installation bid waiting behind your results and no reason to sit on them.
Call (602) 584-7430 or tell us about your parcel online. We schedule fieldwork fast and deliver permit-ready reports in 48 hours.
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