Every district has one. The well that failed its last test, lost its pump and was never re-equipped. The well that went dry in the drought. The old well by the yard that nobody has run since before the current operators were hired. It sits there with a plate bolted over the casing, and it feels like it is doing nothing.
It is doing something. An unused well is a straight, open pipe from the surface into the aquifer every other well in the basin draws from — and often into more than one aquifer, connecting zones that nature kept apart. Surface runoff, a spill at the wellhead, poor water from a shallow zone: all of it has a path down that casing. That is why California treats destroying a well properly as an obligation, not a courtesy.
This note covers when a well has to be dealt with, who may do the work, what the California Well Standards require, and the record a district should keep afterward.
When a well counts as abandoned
The California Well Standards define an abandoned well as one that has not been used for one year, unless the owner shows an intention to use it again. A well the district does intend to use — a standby well, a well waiting on a new pump — can be kept as an inactive well, but it has to be maintained so it cannot become a conduit or a hazard, with a secure cover that keeps people and contaminants out.
So the real question for every idle well on the books is simple: what is the plan for it? “Standby” with a date and a budget is a plan. “We might need it someday” is how a well becomes abandoned by default.
Who may do it
Two rules govern who does the work and how it is recorded.
- A licensed contractor. California Water Code section 13750.5 says no one may abandon or destroy a well unless the person responsible holds a C-57 Water Well Contractor’s License. Destruction is well work, not demolition.
- A permit and a report. The local enforcing agency — usually the county’s environmental health department, sometimes a city or water agency — issues the destruction permit and may inspect the sealing. And like construction, destruction must be reported to the Department of Water Resources on a well completion report within 60 days of finishing the work, under Water Code section 13751.
What the standards require
Part III of the California Well Standards sets out the destruction requirements. The purpose is stated plainly: protect the groundwater for future use, and eliminate the physical hazard. In practice the work runs in four steps.
1. Find out what is down there. The standards require an investigation of the well’s condition, its construction details, and whether there are obstructions. This is where the well completion report earns its keep: casing diameters and depths, the screened intervals, the annular seal, and the geologic log telling you where the clay layers are. A downhole video survey fills in what the paper cannot — collapsed casing, a lost pump column, debris.
2. Clean it out. Pull the pump and anything else in the hole, and remove debris, oil from oil-lubricated pumps, and any pollutants or contaminants. If contamination is known or suspected, the enforcing agency must be told before the work goes further. An enclosed-lineshaft turbine that ran on oil for thirty years can leave a real layer of it floating in the well.
3. Fill it from the bottom up, in one continuous operation. The fill goes in from the bottom of the well upward, placed so it cannot free-fall, dilute or separate — in practice through a tremie pipe lowered to the bottom and raised as the well fills. Where the well must be sealed, the material has to be genuinely impervious: neat cement, sand-cement grout, concrete or bentonite clay, with a permeability below 10 feet per year. Where a seal is not required, fill materials such as clay, silt, sand, gravel, crushed stone or native soil can be used.
4. Seal the places that matter. Three rules do most of the work:
- The top 20 feet of the well is sealed with sealing material, so nothing from the surface can find its way down.
- Across every confining layer, the well is sealed with impervious material for at least 10 feet, so a well that connected two aquifers stops connecting them. This is the rule that protects the deeper, cleaner water from the shallower zone.
- In urban areas, the casing is removed to 5 feet below the ground surface, so the site can be built on and nobody finds a steel pipe with a lawnmower.
How much fill a well takes
The volume matters for the budget and for the inspection, because a sealed interval that took less material than the hole holds has a void in it somewhere. The arithmetic is the volume of a cylinder:
cubic feet per foot of depth = 3.1416 ÷ 4 × (inside diameter in inches ÷ 12)²
A 16-inch casing with a 15.375-inch inside diameter holds:
3.1416 ÷ 4 × (15.375 ÷ 12)² = 1.29 cubic feet per foot
600 feet of casing = about 773 cubic feet, or about 29 cubic yards
If the destruction design also grouts the gravel pack outside the casing, add that volume, then compare the total against what the contractor’s tickets say went in. Where the numbers disagree by much, ask why before the permit is signed off.
Before you destroy it, ask whether it could still work
A well that can no longer produce may still be valuable as a monitoring well. Static water levels from an existing deep well, in the right place, are exactly what a groundwater sustainability agency’s monitoring network needs, and they cost far less than drilling a new monitoring well. Whether an old production well is suitable depends on its construction, its seal and where its screens are — questions the well’s record answers — and the local enforcing agency and the GSA will have views. It is a question worth asking once, before the cement truck arrives.
The record outlives the well
When the work is done, the well is gone from the ground, but it should not be gone from the record. Keep it, marked destroyed, with:
- the date and permit number,
- the contractor and license number,
- the sealing record — materials, intervals and volumes,
- the DWR completion report for the destruction,
- and everything the well’s record held before: its construction, its tests, its history.
Groundwater agencies build their well inventories from these records, a future driller working nearby will want to know what is down there, and the district’s own asset register should be able to explain why a well number stopped reporting production.
What to do with this on Monday
- List every well that has not run in the last twelve months. Each one is either standby with a plan, or abandoned under the standards.
- For each standby well, write down why it is kept, what it would take to return it to service, and confirm the cover is secure.
- For each well with no plan, pull its completion report and decide: destroy, or offer it to the GSA as a monitoring well.
- Budget destruction as a project, with a C-57 contractor, the county permit, the fill volume and the DWR report in the scope.
- Keep destroyed wells in the record, marked destroyed, with the sealing details.
Quick answers
When is a water well considered abandoned in California?
Under the California Well Standards, when it has not been used for one year, unless the owner demonstrates an intention to use it again. A well kept for future use must be maintained as an inactive well, with a secure cover.
Who can destroy a water well in California?
A contractor holding a C-57 Water Well Contractor’s License, under Water Code section 13750.5, working under a permit from the local enforcing agency. The destruction must be reported to DWR on a well completion report within 60 days.
How is a well destroyed properly?
Investigate its construction and condition, remove the pump, debris and any oil, then fill it from the bottom up in one continuous operation. The upper 20 feet and at least 10 feet across each confining layer are sealed with impervious material such as neat cement, sand-cement grout, concrete or bentonite; in urban areas the casing is removed to 5 feet below ground.
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Sources
- California Department of Water Resources. California Well Standards, Part III: Destruction of Water Wells. Source for the purpose of destruction, the one-year definition of an abandoned well, inactive wells, the preliminary investigation and clean-out, sealing and fill materials (permeability below 10 feet per year), bottom-up continuous placement, the 20-foot upper seal, 10 feet across confining formations, and casing removal to 5 feet in urban areas.
- California Water Code. Section 13750.5. Source for the C-57 Water Well Contractor’s License requirement to abandon or destroy a well.
- California Department of Water Resources. Well Completion Reports. Source for the 60-day report requirement for constructing, altering or destroying a well under Water Code section 13751.
Every link above was retrieved and read on 2026-09-26. Paid standards are named by designation so you can check them against your own copy.