The four hour well yield test is used to determine the production or yield of the well in gallons per minute. When required by Environmental Health Services, this test must be performed by a licensed well driller or licensed pump contractor. A current four hour well yield report can be required for a number of reasons.
Depending upon the circumstance, it might be needed prior to building permit issuance or prior to issuance of an Environmental Health Services Final which is needed for a Certificate of Occupancy or as a requirement for a land division. Longer and more detailed testing may be required when there is concern of low well yields.
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Private water wells have a certain structure once complete. A water well cross-section (PDF) shows distinct features.
The well's defenses against contamination are its surface sanitary seal, annular seal, and well casing. If the annular seal is too shallow, the casing ruptured, or the surface seal broken by holes or missing gaskets, contaminants can enter the well. If a well is located too close to a source of contaminants, these may enter through one of these routes or percolate down through the ground, and enter the well at depth.
Lake, river and ditch water - is it legal and safe to drink? Important information on untreated surface water. Ditch Water Pamphlet pdf
During heavy rains or floods, if flood waters or debris are observed around your well casing, the well water becomes cloudy or muddy, or the water tastes "off," your well may have become contaminated. You should check you well's surface sealing characteristics and flush and disinfect the well immediately. Contaminated wells may contain waterborne disease bacteria.
Your well may need to be disinfected. See our disinfection procedure (PDF), or contact our office.
Historically, many properties in Placer County utilized hand dug wells. A hand dug well is not considered a source for potable water supply and can be a threat to your health as well as to the ground water.
When a building permit involves plumbing, it is necessary to demonstrate that the water supply meets potable requirements. A water well might become contaminated with bacteria and be unsafe for use. One individual might be less sensitive than others who might use the water.
Only a well driller with a C-57 license can apply for and obtain a well permit.
The bacteriological analysis must be performed by a California State Certified Laboratory. Any California State Certified laboratory which performs this test is acceptable. Environmental Health Services can provide a list of other local laboratories that provide this service. It should be noted that this list is not a recommendation.
All bacteriological analysis results must be accompanied by a chlorine residual test result. The water sample must be collected in a sterilized sample container provided by the laboratory.