500-Foot Well Drilling Cost

Where 500 feet is the typical residential depth

Across most of the interior West and arid Plains, 500 feet is what residential wells require to reach productive aquifers. The Snake River Plain in eastern Idaho, the basalt-overlain valleys of eastern Oregon and Washington, the Rocky Mountain foothills from Colorado north to Montana, the Trans-Pecos and Permian Basin of west Texas, parts of New Mexico, and the higher elevations of California's Sierra foothills. The water table in these regions sits deep because of low precipitation, slow recharge and (in many places) decades of overdraft.

Per USGS groundwater decline data, water tables in the Ogallala-bordered High Plains and across much of the Southwest have dropped 50 to 150 feet over the past 60 years. New wells in these regions are drilled deeper than the previous generation; a 500-foot well today is the rough equivalent of a 350-foot well drilled in 1965. The state water-rights agencies (Colorado Division of Water Resources, Wyoming State Engineer's Office, Arizona Department of Water Resources) track historical well completions in publicly accessible databases that confirm this trend.

Cost breakdown for a representative bid

Take a 500-foot well in central Colorado, drilled through 80 feet of alluvial gravel into 420 feet of fractured granite and gneiss. Six-inch steel casing is set 80 feet to seal off the alluvium and meet state surface-casing requirements. The remaining 420 feet is open bore through bedrock. A 2 HP submersible pump is set at 480 feet on galvanized drop pipe. An 86-gallon pressure tank goes in the basement.

Line items at 2026 rates. Mobilisation $1,200. Drilling 80 feet through alluvium at $32 per foot ($2,560). Drilling 420 feet through granite at $55 per foot ($23,100). Six-inch steel casing 80 feet at $16 per foot ($1,280). Grouting 50 feet, $750. Well cap with pitless adapter, $300. Development 8 hours, $960. Submersible pump 2 HP with control box, $2,800. Galvanized drop pipe 480 feet at $5 per foot ($2,400). Submersible cable 480 feet (10 AWG), $1,200. Pressure tank 86 gallon, $1,200. Trench from well to house 250 feet, $1,000. State permit and water test $400. Subtotal: $39,150. With 10 percent contingency, $43,065. That is a typical upper bid for central CO at this depth.

Drilling alone ($25,660) is 65 percent of subtotal. Pump-and-electrical-and-tank package ($7,600) is 19 percent. Casing-grouting-cap ($2,330) is 6 percent. Everything else (mobilisation, development, trench, permit) is 10 percent. The pump-and-electrical share is higher than at shallower depths because the bigger pump, longer drop pipe and heavier cable all cost more.

Casing and grouting standards at 500 feet

Most western states require surface casing extended at least 18 to 25 feet below the static water level, or to bedrock, whichever is deeper. On a 500-foot well in country with a 60-foot static water level, that typically means 80 to 100 feet of surface casing. The casing is grouted in the annular space (between casing and bore wall) using cement or bentonite to prevent surface water from tracking down the outside of the casing into the aquifer.

The grouting standard varies by state but the basic spec is similar: cement grout from the surface to 20 feet below ground (or deeper), then bentonite chips to the bottom of the cased zone. California Bulletin 74 well-standards and analogous codes in Oregon, Washington, Idaho, Colorado, Wyoming, Montana and Arizona are the relevant references. The drilling permit usually requires the driller to file a completion report including the actual grouting method and depth.

At 500 feet in hard rock, the cased portion is small (the upper 80 feet) but the grouting is more demanding than at shallower depths because the column of grout has to be tremied down through the annulus without bridging. A failed grouting job (bridges, voids in the column) is a code violation that can fail the inspection and require redo at $800 to $2,500. Worth confirming the driller's grouting method up front.

Pump, drop pipe, electrical at 500 feet

The pump configuration at 500 feet is where the engineering margins get tight. A 2 HP submersible pump is the minimum spec for a 4 to 5 person household at this depth; some installers go to 3 HP for larger households or where the static water level is below 100 feet. The pump must lift 500 vertical feet plus overcome drop-pipe friction loss; the standard sizing assumes a working pressure of 60 psi at the tank and a peak flow of 12 to 15 gpm.

Drop pipe. Schedule-80 PVC is below its safe working stress at 500 feet in most configurations. Galvanized steel or stainless-steel drop pipe is the standard. Galvanized runs $5 to $6 per foot installed; stainless runs $9 to $12 per foot. The 480-foot drop costs $2,400 to $5,800 depending on material. Stainless adds about $3,000 to the total bill but doubles the realistic service life (40 to 50 years vs 20 to 30 for galvanized in mineralised water).

Submersible cable. Cable is sized for voltage drop at the pump motor at start-up. At 500 feet with a 2 HP pump on 230V, the National Electrical Code requires 10 AWG cable (12 AWG would drop too much voltage to start the motor reliably). Cable runs $2 to $3 per foot installed. The 480-foot run is $1,000 to $1,500. Worth confirming the gauge on the bid; some installers try to economise with 12 AWG and the pump short-cycles or fails to start under load.

Pressure tank. An 86-gallon tank (with 28 gallons of working drawdown) is the right sizing for a 2 HP pump at 500 feet. Smaller tanks cause too much pump cycling, which is the dominant failure mode at this depth (pumps that cycle every minute under heavy household demand wear out in 5 to 8 years instead of 15 to 20). The marginal $400 for the bigger tank pays back many times over.

Yield expectations at 500 feet

Yield varies more at 500 feet than at any shallower depth, mostly because the geology gets more variable as you go deeper. In confined sand-and-gravel aquifers (parts of Idaho, Washington, Oregon, the Mississippi alluvial valley), 500-foot wells routinely produce 20 to 40 gpm and are some of the most productive residential wells in the country. In fractured granite, 500-foot wells can produce anywhere from 1 to 30 gpm with no reliable predictor before drilling. In basalt (Pacific Northwest), the fracture and joint systems control yield and the variability is similar to granite.

A 500-foot well producing less than 3 gpm is a marginal residential supply. Options: hydrofracture (works best in fractured-rock wells, less in basalt or alluvial), deepen another 100 feet, add a 1,000 to 3,000 gallon storage cistern to buffer low yield, or accept the well as a backup and consider water-hauling or a shared well agreement with neighbours. The cost-effectiveness analysis between these options depends on the specific yield, the local water-hauling cost ($100 to $300 per 1,000 gallons in most rural markets) and the household's water-use pattern.

When 500 feet becomes "too deep" economically

At 500 feet, the marginal cost of going another 100 feet is around $4,500 to $7,000 in hard rock. Hydrofracturing the existing bore costs $1,500 to $4,500. A 3,000-gallon storage cistern installed costs $4,000 to $8,000. Water hauling at $200 per 1,000 gallons delivered, at typical rural-household usage of 300 gallons per day, costs $1,800 per year (about $36,000 over 20 years). Municipal connection where available costs $5,000 to $15,000 plus monthly fees.

For most homeowners with a low-yield 500-foot well, the right answer is hydrofracture first (cheapest, fastest, 70 to 85 percent success rate per NGWA), then a storage cistern if the well still under-produces, then deepening as a last resort. Drilling to 800 feet (see 800-foot well drilling cost) is the threshold at which "is there any way to avoid this" becomes a serious question.

Cross-references and adjacent depths

For the per-foot rate, well drilling cost per foot 2026. Shallower bracket, 400-foot well drilling cost. Deeper bracket, 600-foot well drilling cost. For pump and drop-pipe details, pump installation costs. For the hard-rock geology that dominates 500-foot drilling, bedrock well drilling cost. For deep-water Arizona context, Arizona well drilling cost.