Well Drilling in Benton County, WA

• Coverage includes Finley, Benton City, Prosser, West Richland, Badger Canyon, Plymouth, Paterson and the Horse Heaven Hills.
• Crews work along I-82, I-182, SR 240, SR 221 and SR 14 along the Columbia.
• Other Washington and Northwest counties on this site: Pend Oreille County, WA and Umatilla County, OR across the river.

• New domestic wells into basalt on acreage lots
• Shallow wells in the Pasco gravels near the rivers
• Pump and pressure tank replacement
• Deepening wells after water levels drop
• Nitrate testing near irrigated farmland
• Decommissioning old wells, which also needs a notice

• Local depth: at the USGS median of about 145 ft, the site calculator's formula gives $5,125–$13,925 for a complete well. At the 75th percentile (about 301 ft) it gives $9,025–$24,065, and at the 90th (about 580 ft) $16,000–$42,200. The site calculator's method is depth × $25–$65 per foot, plus permit $200–$500, pump $900–$2,500 and tank $400–$1,500. It is an estimate, not a quote.
• Notice fee: WAC 173-160-151 sets $200 for a well with a casing under 12 inches and $300 for 12 inches or more, and $50 to decommission a well.
• Basalt drilling is slower than gravel, and deep basalt wells on the Horse Heaven Hills run toward the top of the cost range.
• Long pump settings in deep basalt wells raise pump and wiring costs.

• Step 1, notice: the driller files a notice of intent with Ecology at least 72 hours before drilling; Ecology says it's a notice, not a permit.
• Step 2, fee: the Washington Administrative Code, WAC 173-160-151, sets $200 for a well with a casing under 12 inches and $300 for 12 inches or larger.
• Step 3, siting: WAC 173-160-171 sets five feet from buildings, 50 feet from a septic tank or distribution box, 50 feet from a sewer and 100 feet from a drainfield or reserve area.
• Step 4, water rights: a household well in Washington uses the permit-exempt allowance under state law; larger uses need an Ecology water right.
• Step 5, records: keep the well report the driller files with Ecology.

• Basalt and gravel: USGS site records for Benton County code 247 wells to the Saddle Mountains Basalt, 237 to the Pasco gravels and 122 to the Columbia River Basalt Group. Groundwater in the basalt aquifer moves along fractured flow tops, the alluvium along the rivers forms a shallow aquifer zone, and bedrock basalt formation outcrop is common on the ridges; deeper wells pass several basalt formation layers.
• Reading the log: along the Columbia and Yakima rivers, near Finley and Benton City, wells finish in sand and gravel of the Pasco gravels and alluvium; south and west, on the Horse Heaven Hills and toward Prosser, wells drill through loess into basalt flows, where water sits in fractured interflow zones between layers. Deeper basalt aquifer zones of the Wanapum and Grande Ronde formations lie below the Saddle Mountains flows.
• USGS site records (n=2,232 with depth): 25th percentile about 61 ft, median about 145 ft, 75th percentile about 301 ft, 90th about 580 ft.
• Census ACS counts about 83,101 housing units with a median year built of 1988.

Finley · Benton City · Prosser · West Richland · Badger Canyon · Plymouth · Paterson