Construction of monitoring wells
Summary of water district standards

Permit and license requirement
Permits are required for all wells. Please call (408) 265-2607, extension 2660, for permit applications or download one [PDF]. There are no fees for permits. Permit applications must be submitted with original signatures. Drilling contractors must have a current California C-57 contractor's license.

A California-registered geologist, certified engineering geologist, certified hydrogeologist, or registered civil engineer must approve, sign, and stamp permit application. There are no temporary installations of monitor wells. All cased borings are considered permanent wells and must be properly permitted and inspected. A separate permit is required for each casing, including nested wells, piezometers, and air-sparging wells.

Annular seal depths and radial thickness
Monitoring wells are not subject to the depth of seal requirements used for water wells. However, monitoring wells should be constructed in a method that they will not serve as a conduit for vertical groundwater flow or cause down-hole migration of surface contaminants. A minimum 5-foot seal is required (vault box is not included as part of seal). Variance for less than a 5-foot seal may be approved by District if shallow groundwater conditions exist. Variances must be approved by the district before drilling. A minimum 2-inch radial thickness of annular seal is required by state well standards. Any excess borehole must be properly backfilled with approved sealing materials. No soil cuttings may be used for backfilling boreholes. Bentonite pellets may only be used for backfill of less than 3 feet of overdrill. If backfilling more than 3 feet of overdrill, 27 sack neat cement, 10 sack cement sand grout, or 20 percent high solids bentonite, slurry must be used.

Acceptable sealing materials
Acceptable sealing materials are 27 sack neat cement (four 94-pound bags/55-gallon drum), 10 sack cement sand grout, or hydrated high solids 20 percent bentonite slurry. No bentonite chips or pellets are allowed except for maximum 3-foot thick transition seal directly above filter pack.

Placement of sealing materials
Free fall of sealing material is not allowed if greater than 30 feet or if more than 3 feet of standing water exists in annulus. A tremie pipe must be used to place the sealing material if seal is more than 30 feet deep or more than 3 feet of water is present in the annulus.