Every water well in California was supposed to leave a document behind when it was built: the well completion report, the form the state calls a DWR 188 and most people in the field still call the driller’s log. It is the well’s birth certificate. What was drilled, how deep, what the ground was made of, where the casing and screen sit, what the annulus was filled with, and how much water the well made on its first test.
Every serious decision about that well for the rest of its life leans on that one document. How deep the pump can be set. Whether a new bowl assembly will even fit down the hole. How much water sits over the top of the screen when the well is running. Whether the seal is deep enough to keep surface water out. Which rehabilitation method is safe for the screen that is actually down there.
And most district staff have never been shown how to read one. This note walks through the form box by box, works one example, and ends with the mistakes that make a well’s record quietly wrong.
Where to get it
Anyone who constructs, alters or destroys a water well in California must file a completion report with the Department of Water Resources within 60 days of finishing the work, under Water Code section 13751. Since the 2015 amendment to section 13752, the reports are available to the public on request, not just to agencies. DWR’s well completion report map lets you search by location, and a request form covers the ones that are not online.
For a district’s own wells, look in three places before you ask the state: the district’s well files, the engineer’s as-built drawings from the original project, and the construction contractor’s closeout package. The as-built usually says more than the DWR form, and the two do not always agree. When they disagree, you have learned something important about that well.
The form, box by box
Well identification. The owner’s well number, the dates work began and ended, and the permit agency and number. The dates tell you which construction standards applied. A well finished before the California Well Standards were adopted was built to whatever the county required at the time.
Location. Address, APN, latitude and longitude with their datum and accuracy, township-range-section, and — the one most people skip — ground surface elevation. Every depth on the form is measured from the ground. Without the elevation you can compare this well with itself, but not with its neighbors, the monitoring network or the basin’s groundwater contours. Note the location accuracy field too: an older report located by section may be off by a quarter mile.
Borehole information. Drilling method, total depth of the boring, total depth of the completed well, and the drilling fluid. Two things to check here. First, if the boring went deeper than the completed well, the bottom was backfilled — find out with what. Second, the drilling method tells you what the formation next to the screen went through. A mud-rotary well depends on development to clear the drilling mud out of the gravel pack; a well that was under-developed on day one often shows it in its first specific capacity.
Geologic log. Depth intervals and a free-form description of what came up: “clay”, “sand and gravel”, “decomposed granite”, “hard blue clay with streaks of sand”. These are the driller’s words, written at the rig, not a geologist’s classification. Read them for two things: where the water-bearing zones are (the coarse, clean intervals), and whether the screen was actually set against them. A screen set against clay produces little water and a lot of trouble.
Casings table. The most important table on the form. One row per string, with depth from and to, casing type (blank or screen), material, wall thickness, outside diameter, screen type and slot size. From it you get the screened intervals, the diameter at every depth, and the inside diameter the pump has to pass through on the way down.
Annular material. What fills the space between the casing and the borehole, by depth: the cement or bentonite seal at the top, the gravel pack around the screen, sometimes a transition seal between them. The California Well Standards require the upper annular seal to reach at least 50 feet on a community water supply well and 20 feet on a domestic or agricultural well, with at least two inches of sealing material around the casing. If the report shows less, you want to know why.
Water level and yield. Depth to first water, static water level, estimated yield, test length, test type and total drawdown. Together they give you the well’s first specific capacity: the baseline every later test is measured against.
A worked example
Here is a made-up report for a municipal well, the kind of thing you would find in a district file. We will read it the way the decisions need it.
| Casing | Depth | Type | Outside diameter | Wall | Slot |
|---|---|---|---|---|---|
| 1 | 0–50 ft | Blank, conductor | 30 in | 0.375 in | — |
| 2 | 0–200 ft | Blank | 20 in | 0.375 in | — |
| 3 | 200–310 ft | Blank | 16 in | 0.3125 in | — |
| 4 | 310–580 ft | Screen, louvered | 16 in | 0.3125 in | 0.080 in |
| 5 | 580–600 ft | Blank, sump | 16 in | 0.3125 in | — |
| 6 | 0–500 ft | Sounding tube | 2 in | Sch 40 | — |
The seal. Cement from 0 to 50 feet on a community water supply well: it meets the 50-foot minimum, just.
The screen. Screen from 310 to 580 feet — 270 feet of it — below a reducer at 200 feet, where the casing steps down from 20 inches to 16. That reducer is the most important line on this form for anyone who will ever pull or replace the pump.
The pump fit. A bowl assembly has to pass everything above its setting depth. Set it anywhere below 200 feet and it has to pass the 16-inch casing, whose inside diameter is:
16.000 in − (2 × 0.3125 in) = 15.375 in
That is the ceiling on bowl diameter below the reducer, before any allowance for clearance, a crooked hole or the sounding tube running alongside. Not the 20 inches at the surface. A district that orders a pump from the wellhead diameter will find this out on the rig.
The water over the screen. Static level 180 feet, 60 feet of drawdown at 1,500 gpm, so the pumping level on the day of the test was 240 feet. The top of the screen is at 310 feet: 70 feet of water over the top of the screen at full rate. That margin is what protects the screen from being pumped dry and cascading, and every foot the aquifer drops or the well plugs comes out of it.
The baseline. 1,500 gpm with 60 feet of drawdown is a specific capacity of 25 gpm per foot after a 24-hour test. That is the number the rest of this well’s life gets compared to — see specific capacity for how to compare it fairly.
Five ways a record goes quietly wrong
- Measuring from the wrong zero. The form measures from ground surface. Field crews often measure from the top of the casing or the sounding tube, which may stand a foot or three above grade. Mix the two and every water level is off by the stickup, forever.
- Reading a sounding tube as casing. Row 6 above is a 2-inch tube for lowering a water level sounder. Read it as a casing string and the tightest diameter in the well becomes 2 inches, and every pump-fit calculation says nothing will go down the hole.
- Missing the nested strings. Rows 1 and 2 both start at the surface. A conductor outside the production casing is normal, and two strings at the same depth are only impossible at the same diameter. Collapse them into one and you lose either the conductor or the casing.
- Treating the estimated yield as a design flow. A short air-lift test at completion tells you the well can make water. It is not a pump test, and it is not a number to size a pump against.
- Inventing a day. An old report often gives only a year, or a month and year. Recording “1986” as January 1, 1986 creates a precision the document never had. Keep the date exactly as precise as the paper is.
What to do with this on Monday
- Pull the completion report for every well you own, and the as-built drawing next to it. List the wells that have neither.
- Record the ground surface elevation for each well, so its water levels can be compared with the basin’s.
- Transcribe the casing and annular tables into the well’s record, one row per string, sounding tubes marked as sounding tubes.
- Work out the inside diameter below every reducer, and write the tightest one above the pump setting on the pump record.
- Write down the first specific capacity and the test it came from. That is the baseline everything after it is measured against.
Quick answers
Where can I find a well completion report in California?
From the Department of Water Resources: its well completion report map application searches by location, and a request form covers reports that are not online. Reports have been available to the public on request since the 2015 amendment to Water Code section 13752.
What is the difference between a driller’s log and a well completion report?
In California they are usually the same document. The well completion report (DWR 188) includes the geologic log — the driller’s description of the ground, by depth — along with the casing, annular seal and first yield test.
How deep does the sanitary seal on a water well have to be in California?
The California Well Standards require the upper annular seal to extend at least 50 feet below ground on a community water supply or industrial well, and at least 20 feet on individual domestic, agricultural and most other wells.
Upload one of your own driller’s logs and see it read into the well’s record, row by row, with a person approving every line. Request a walkthrough →
Sources
- California Department of Water Resources. Well Completion Reports. Source for the 60-day filing requirement under Water Code section 13751, the online filing system, the map application and the request form.
- California Water Code. Section 13752. Source for reports being available to the public on request, as amended by Stats. 2015, ch. 24 (SB 83).
- California Department of Water Resources. California Well Standards, Part II: Water Well Construction. Source for the 50-foot and 20-foot minimum upper annular seal depths and the two-inch minimum seal thickness (Section 9).
- California Natural Resources Agency. Well Completion Reports dataset. Source for the tabulated completion report data published by DWR.
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.