Sonoma County Municipal Code Art. III Well Abandonment

(a) Abandoned Wells. All abandoned wells and abandoned borings shall be destroyed in accordance with the requirements of this chapter.

(b) Inactive Wells. A well may not be considered abandoned if the owner declares in writing to the enforcing agency his or her intention to use such well again for supplying water or for other approved purposes, and if such well has no defects in construction. All inactive wells shall be provided with a watertight cover at the top of the well or well casing. Such cover shall be secured by locks or by other means that prevents removal of the cover without the use of equipment or tools. The well shall also be marked so as to be clearly seen, and the ground surrounding the well shall be sloped away from the casing and kept clear of brush, debris and waste material.

(c) Uncompleted Wells or Borings. Any well or boring that is not completed as a finished well shall be destroyed by the well drilling contractor in accordance with this section and the California Well Standards Bulletin 74-81 prior to leaving the site.

(1) Wells or borings shall be backfilled with the same soil excavated or sand, gravel and/or rock to such a degree that ninety (90) days after completion of backfill, such backfill is at or above surrounding ground level.

(2) An alternate method is to fill such hole with equivalent sealing materials (see Section 25B-11).

(3) If any water is encountered, the top thirty feet (30') shall be sealed with proper seal or grouting material. From the bottom of the well or boring to thirty feet (30') from the surface, clean, uncontaminated sand or gravel may be used.

(d) Well Destruction. Prior to destroying a well, a report on the well shall be submitted to the enforcing agency by a well contractor. Such report shall indicate the type of well to be destroyed, all known information regarding the geological conditions of the soil and water strata and the methods and materials to be used in the destruction and sealing process. The methods and materials used in destroying wells and test holes shall be such that the usable ground water is protected from contamination or the entrance of surface water thereto. All wells shall be destroyed as follows:

(1) Any obstruction in the well shall be removed when possible.

(2) A hole, at least one foot (1') larger in diameter than the drilled hole, shall be excavated around the well casing to a maximum depth of five feet (5') below ground surface. The well casing shall be cut off six inches (6") above the bottom of the excavation and removed. Under no circumstances shall the casing extend above the ground surface. The well driller may propose alternative methods of destruction (see Section 25B-11) for those wells where physical access limits the ability to remove the casing.

(3) The remaining casing shall be ripped or perforated from the surface to a depth of thirty feet (30'), or deeper as required by the enforcing agency. The well driller may propose alternative methods of destruction (see Section 25B-11) for those wells where physical access limits the ability to remove the casing. This provision shall only apply to wells that do not have a permitted annular seal.

(4) The placement of the material shall be done in such a way as to avoid bridging and to assure a dense seal, in order to exclude water intrusion.

(i) The well shall be filled with the appropriate material from the bottom of the well up.

(ii) The well shall be filled to within not more than thirty feet (30') from the surface with uncontaminated clay, sand or other approved material (see Section 25B-11), then sealed, in one (1) continuous operation, to a depth of at least thirty feet (30') with approved sealing materials as described in the well destruction permit application. The sealing material shall spill over into the excavation, forming a cap. After the sealing material has set, the excavation shall be filled with compacted native soil.

(iii) When there is water present, sealing material shall be placed in the interval to be sealed by methods (such as the use of a tremie device or equivalent) that prevent free fall, dilution, and/or separation of aggregates from cementing materials.

(iv) In cases where a tremie device is used, the tremie device shall be lowered to the bottom of the zone being sealed, and raised slowly as the material is introduced. The discharge end of the tremie device shall be continuously submerged in the sealing material until the zone to be sealed or filled is completed.

(e) Large Diameter Wells. Destruction of large diameter wells shall be in compliance with the standards described in "CGA Standard Practices". As much of the liner as possible (or safe) shall be removed prior to filling. Other methods providing equivalent aquifer protection may be approved by the enforcing agency (see Section 25B-11).

(f) Contaminated Well. Upon determination by either enforcing agency listed in Table 25B-1 that a well is contaminated, or is a potential hazard to the purity of the underground waters, and reasonable efforts to clear the contamination have been unsuccessful, the enforcing agency, shall have the authority to:

(1) Enforce permanent destruction of said well in accordance with the provisions listed in this section and/or those destruction standards or methods required by the agency with primary regulatory oversight, or

(2) Review proposals for continued use of the well in accordance with the provisions listed in Section 25B-8.

The property owner shall be responsible for the destruction, abandonment, capping, continued maintenance, monitoring or studies of such wells or test holes.

(g) Contaminated Well Studies. The enforcing agency shall have the authority to require studies of contaminated wells to determine proper destruction techniques, to determine if the well presents a threat to groundwater or to other wells or to determine if the well is in compliance with other requirements of this Code.

(h) Temporary Capping of Wells.

(1) A contaminated well may be temporarily capped for up to five (5) years or until efforts to remediate contaminated ground water have been successfully accomplished.

(2) A contaminated well that is screened across two (2) or more water bearing zones and/or has the potential to contaminate non-contaminated water bearing zones, packers shall be installed in addition to the temporary cap.

(3) The enforcing agency may extend the five-year time period if necessary to accommodate the ground water remediation process. The enforcing agency may approve alternative methods of water supply while remediation efforts are in progress.

(i) Alternative Water Supplies. The enforcing agency may approve alternative water supplies in order to insure a potable water supply. These may include hauling potable water to an approved storage tank and pressure system or other methods that will insure a continued source of potable water.

(j) Contaminated Well Exemption Criteria. A contaminated well need not be destroyed if the well meets the following criteria:

(1) The continued use of the well complies with all applicable state of California regulatory requirements; and,

(2) The continued use of the well does not impair or exacerbate a ground water investigation or cleanup project; and,

(3) The Sonoma County DHS has made a determination that continued use of the well is protective of public health; and,

(4) The continued use of the well complies with the well water treatment provisions of Section 25B-8.

(Ord. No. 6422, § I(Exh. A), 4-18-2023)