What a Prunedale Well Has to Prove, and When It Has to Prove It

For an existing private well, Monterey County's Environmental Health Bureau speaks mostly in guidance. Its drinking-water FAQ makes the private-well owner responsible for water safety and recommends testing a private well at least once each year. Before buying, ask the County directly what applies to a specific transfer.

The County's measurable standards come into play when the land has to support something new. Every single-family dwelling and subdivision proposal is reviewed for adequate water supply. A well proposed to supply a new home must pass a continuous pumping test that the County witnesses, and new single-connection domestic wells must also pass a laboratory panel. For anyone buying acreage in Prunedale, Las Lomas or the Aromas area with plans to build, add a home or split the land, the purchase and the water test can happen years apart. How hard that test will be depends on two things a listing sheet seldom shows: the rock the well draws from, and the groundwater basin the parcel sits in.

The standard a well meets when someone builds

The County's source-capacity procedure sets a minimum yield based on how many connections a well serves.

The length of the test depends on the geology. The procedure calls for at least 8 hours of continuous pumping in alluvial formations and at least 72 hours in non-alluvial formations. Each test is followed by a recovery period as long as the pumping time. Every new single-connection domestic well must also be tested by a California-certified laboratory for coliform, secondary standards, and an inorganic panel that includes arsenic, nitrate and nitrite. The County's standards sheet lists the maximum contaminant levels as 0.010 mg/L for arsenic and 10 mg/L for nitrate as nitrogen. Its FAQ gives the nitrate limit as 45 mg/L when measured as nitrate.

Parcel size matters too. If a lot uses onsite sewage disposal and could be served by a water system, the County says it must be at least 2.5 acres to get a well-construction permit.

Why the rock under a parcel changes the math

The 8-hour and 72-hour thresholds track the geology of Prunedale closely. The Langley Area Subbasin, which contains Prunedale, is mostly semi-consolidated sedimentary deposits forming low hills, with fractured granite beneath. Granite outcrops define its northeast edge. The Water Year 2025 annual report from the Salinas Valley Basin Groundwater Sustainability Agency describes fractured-granite wells near the Gabilan Range as inconsistent or unreliable. It also notes that decomposed granite and the Aromas Sands both provide water.

So two parcels a short drive apart can face very different paths to a building permit. A well in the Aromas Red Sands may meet the standard on an ordinary schedule. A well drilled into the granite toward the Gabilan foothills falls into the longer non-alluvial test, and the agency already calls that formation unpredictable. On acreage priced for its building potential, that difference belongs in due diligence, before price negotiation.

The basin line runs through North County, and it sets the bill

The second variable is the agency. North Monterey County is not a single groundwater unit. North of Langley, a drainage divide separates it from the Pajaro Valley Groundwater Basin. That divide is an old Salinas River channel filled with fine sediments that may limit groundwater flow between the two basins. The Pajaro Valley Water Management Agency covers about 75,000 acres across southern Santa Cruz County, northern Monterey County and a small part of San Benito County. Its area map names Aromas and Las Lomas. PV Water publishes an address-search map for its boundary, because county location alone doesn't tell you which agency applies.

The two structures for an ordinary household well look like this:

SVBGSA adopted the Langley figures on July 9, 2026, which brings a Langley domestic connection to $21.65 a year. On the Pajaro side, the posted charges come to $181 a year for one residential parcel with one rural residence. The two numbers measure different things. PV Water's charge is an augmentation charge tied to estimated pumping. SVBGSA's is a regulatory fee per connection.

PV Water's 2026 cost-of-service proposal pulls in two directions. The proposed metered rates rise to $363 per acre-foot outside the Delivered Water Zone and $504 inside it. The proposed rural-residential charge falls to $132, because the estimated household use drops from 0.5 to 0.4 acre-feet. The board's September 16, 2026 agenda listed hearings on Ordinances 2026-01 and 2026-02. As of early October 2026, the agency's posted records showed no minutes or adopted ordinance, so the December figures are still proposals. PV Water does not list a meter requirement for an individual domestic well below its thresholds. Metering applies to wells pumping at least 10 acre-feet a year and to wells serving 15 or more connections. The agency also excludes the area east of the San Andreas Fault from its augmentation charge.

The low Langley fee sits on a basin still short of its goals

Langley's small fee could suggest a settled basin. The agency's own numbers show otherwise. In Water Year 2025, which ran from October 1, 2024 to September 30, 2025, groundwater extraction was about 1,730 acre-feet, and average groundwater levels rose 1.2 feet in a dry-normal year. Three monitoring wells with established criteria still sat below their minimum thresholds, and four groundwater-quality constituents exceeded theirs. The subbasin recorded undesirable results for chronic lowering of groundwater levels and reduced groundwater storage. The agency says none of the water-quality exceedances were caused by its management actions or inaction. No seawater intrusion or subsidence was detected.

The draft amendment shows where rural households fit in what comes next. SVBGSA's Langley page posts draft GSP Amendment 1 and names January 14, 2027 as the intended public hearing date. The draft adds two actions aimed at rural residents. MA4 offers voluntary efficiency services such as home water-use assessments, leak repair and fixture rebates. MA5, Rural Residential Well Mitigation, covers well registration, groundwater-level tracking, dry-well reporting and notification systems. Its cost is listed as "Not yet determined." The draft's demand-management framework keeps allocations or pumping limits available as possible future tools, though it states that this action does not set them itself. In September 2026, SVBGSA extended its free Water Efficiency Pilot Program to rural residents in all six subbasins, including Langley, through the end of 2026.

The County runs a separate per-well program on top of these. Every well in the Groundwater Monitoring Program area must be registered, and owners must update the record after a change of ownership. For FY 2026–27, the County kept its prior rates: $160.16 for initial registration, $21.86 for annual renewal and $117.68 for groundwater-level monitoring. Which fees apply depends on the well, its location and its use. Domestic wells pumping two acre-feet or less a year are exempt from extraction reporting. At its June 23, 2026 meeting, the County was still seeking one-time Measure AA funding to cover de minimis well costs and supporting AB 2728 to allow fee exemptions for small users.

Questions to settle before an offer on North County acreage

1. Which basin and agency? Check the PV Water address map, and confirm Langley or Eastside status with SVBGSA.
2. What formation does the well draw from? The well log and a licensed well professional can tell you whether the well is in sands, decomposed granite or fractured granite, which tells you whether the 8-hour or the 72-hour test would apply.
3. Is there a recent certified lab result? Ask for coliform, arsenic and nitrate results at a minimum. The County recommends annual testing for private wells.
4. Is the well registered with the County? If so, plan to update the record after the ownership change.
5. What do your plans for the land require? A second home or a lot split raises the minimum yield. A shared system serving 2 to 14 connections has its own change-of-ownership permit.

For anything about permit eligibility or legal obligations, bring in your own licensed well contractor, attorney or the County directly.

A few questions worth asking

Does the 41 percent nitrate figure in the news apply to household wells in Prunedale? No. KAZU reported in September 2025 that 41 percent of Monterey County farm wells sampled through the Central Coast Water Quality Preservation program exceeded the nitrate limit. That figure covers sampled farm wells countywide. It does not measure household wells in Prunedale. A lab test on the specific well is the only reliable answer.

Is a public water supply coming to replace Prunedale wells? The County's Granite Ridge Regional Water Supply Project page lists documents from 2008 to 2010 and does not show the project as funded or under construction. SVBGSA's Langley report says CSIP operates outside Langley and does not immediately affect its groundwater. Pure Water Monterey serves the Monterey Peninsula.

Do state well-permit rules restrict a new household well? Executive Order N-3-23 kept the N-7-22 well-permit review for medium- and high-priority basins. It exempts individual domestic wells producing less than two acre-feet a year from that extra review. The ordinary County permit, with a C-57 licensed contractor, still applies.

If you are weighing acreage in Prunedale, Las Lomas or the Aromas area, Kathleen Manning can help you confirm the basin, pull the well records and line up the right experts before you make an offer. Let's Connect.