Merced Municipal Code Art. IV Well Construction Standards

A. Except as may be specified in this chapter, the standards for the location, construction, sealing, maintenance, rehabilitation, modification, abandonment, or destruction of wells, exploratory holes, and test wells shall be those published in Chapter ii and Appendixes B, C, and D of the "State Water Well Standards" (DWR Bulletin 74-81 as revised in 1988 or the latest revision), Chapter II of the "Monitoring Well Standards" (DWR Bulletin 74-88 or the latest revision), and Chapter II of the "Cathodic Protection Well Standards" (DWR Bulletin 74-1 as revised in 1988 or the latest revision).

B. Well Integrity.

1. All wells, exploratory holes and test wells shall be constructed to prevent the entrance of surface water or foreign material from any source into the well, hole or aquifer.

2. All wells shall be located, constructed, maintained, rehabilitated, modified, abandoned or destroyed so the quality of the ground water is not degraded.

3. Drainage wells which are used for dewatering agricultural areas which discharge only to irrigation facilities are exempt from the sealing requirements, except when they penetrate the Corcoran Clay or cause or threaten to cause the spread of pollution. Surface protection and safety from hazard standards shall be provided.

4. Construction of a well in a pit is prohibited except for agricultural dewatering wells which discharge only to irrigation facilities.

5. In special situations where pollution or contamination of ground water is known, the city may modify these standards or otherwise prescribe special requirements to ensure the quality of the ground water, and the health and safety of the people. If, in the opinion of the director, special conditions or construction will not adequately safeguard the quality of the environment or the health or safety of the public, then the director shall deny such a permit.

(Ord. 1754 § 1, 1990).

A. Wells shall be located an adequate distance from known or potential sources of pollution to prevent degradation of water quality.

B. No wells shall be located within fifteen feet of a property line.

C. Separation between a drinking water well and any well which has no upper annular seal or sanitary seal shall be at least three hundred feet.

D. No well shall be located closer to a potential source of pollution than the distance listed below in Table 2. When, in the opinion of the director, adverse conditions or unusual sources of pollution exist which may cause degradation of water quality, distances prescribed in Table 2 may be extended by the director.

Table 2 Distance Between A Well and Potential Sources of Pollution

E. Exemptions from Table 2 may be granted by the director for monitoring wells and cathodic protection wells.

(Ord. 1754 § 1, 1990).

A. Well Sealing.

1. Sealing conditions and procedures prescribed in Sections 9 and 13 of DWR Bulletin 74-81 as revised in 1988 or the latest revision, Section 11 of DWR Bulletin 74-88, and Sections 10 and 11 of DWR 74-81 as reviewed in 1988 or the latest revisions, are considered standards for this chapter, except as provided below.

2. A well shall be sealed with a sealing material in a manner that prevents bridging, dilution, or segregation of the grout which would prevent the material from completely filling the annular space. The suggested methods for sealing given in Appendix B of DWR Bulletin 74-8 1 are the minimum standards for this chapter. Other methods of sealing the annular space may be approved upon review by the director after reviewing a written request by the owner for an alternative method.

3. Sealing material shall be of a composition equivalent to those given in Section 9 of DWR Bulletin 74-8 1 as reviewed in 1988, or the latest revisions and Section 11 of DWR Bulletin 74-88 or the latest revisions.

4. Wells shall be constructed so the annular space is effectively sealed at the surface to protect against contamination or pollution by entrance of surface or shallow subsurface waters. At a minimum, new wells shall be sealed from the surface in accordance with the following Table 3.

Table 3 Minimum Depth of Surface Seal

5. Wells which penetrate the Corcoran Clay shall be constructed in a manner to prevent production or mixing of waters from above and below the Corcoran Clay.

6. Annular seal shall extend from the surface to a depth of at least three hundred feet for new wells producing water from a depth below three hundred feet.

7. Where a well penetrates more than one aquifer and mixing of aquifer waters in sufficient quantities will cause significant deterioration of the quality of water in one or more aquifers, then the strata producing the poor quality water shall be sealed off. New wells shall not be allowed to tap two or more separate and distinct producing zones (aquifer systems).

8. If any existing well producing water from both the intermediate aquifer and the Mehrten aquifer is found to be contaminated, it shall be modified to seal off the contaminated zones and to prevent mixing between aquifers or shall be destroyed.

9. When special conditions exist, such as known pollution, the director may prescribe additional sealing standards to prevent the migration of pollution.

B. Casing Materials.

1. All new and rehabilitated wells shall be constructed with casing materials which have sufficient strength and durability to resist the forces imposed on it during installation, including grouting and development, and which will provide structural integrity against forces which can normally be expected after installation. No thermoset or thermoplastic casing greater than eight inches in nominal diameter will be allowed below a depth of three hundred feet.

2. Casing material and thickness of material shall be selected in accordance with good design practices. Materials selected for the well casing shall be of a strength and durability that meets the specifications prescribed in Section 12 of Chapter II of DWR Bulletin 74-81 as revised in 1988 or the latest revision, or Section 9 of Chapter II of DWR Bulletin 74-88 or the latest revision.

C. Surface Construction.

1. All pumping equipment shall be installed with protective devices to effectively prevent entrance of foreign matter or back siphonage into the well casing. A properly designed air gap may be considered an acceptable protective device for agricultural wells.

2. A concrete slab or base shall be constructed around the top of all water wells. The top of the floor slab shall be sloped away from the casing. The floor slab shall be a minimum of six inches thick with the outer edge of the slab at least four inches above and at least two inches below the ground surface, The surface slab shall be tied to the well's annular surface seal.

3. All wells furnishing water for human consumption shall have a greaseless petcock valve with the spout facing down located on the discharge line before the storage tank for obtaining water quality samples.

4. Any well terminating above the ground surface in areas where vehicular traffic can occur must be identified and protected such that the well can easily be seen and protected from damage.

5. Where the top of a monitoring or cathodic protection well must be below the ground surface, a concrete or other water tight vault must be installed. The vault and its lid must be strong enough to support vehicular traffic. The top of the vault should be set so drainage is away from the vault. The well must be capped with a leakproof cap so water in the vault will not enter the well. The vault cover or lid must be leakproof.

D. Well Development.

1. Development or redevelopment of a well shall be done in a manner which will not cause damage to the well or cause adverse subsurface conditions that may destroy barriers to vertical movement of water,

2. Developing or redeveloping of a well by using explosives is prohibited unless a special variance is granted by the director.

3. Developing or redeveloping of a monitoring well shall be done in a manner which does not interfere with the analytical results of water quality sampling. In areas of known ground water pollution, development fluids shall be handled, stored and disposed of in accordance with all applicable state and county department of health standards and procedures.

E. Well Disinfection.

1. All well and associated equipment furnishing or in contact with potable water for domestic use shall be disinfected after construction, installation or repair of the well, pump or storage equipment and before use of the water or return of the well to operation.

2. Suggested methods for disinfection given in Appendix C of DWR Bulletin 74-8 1 as revised in 1988 or the latest revision are required.

F. Water Sampling.

1. Before, and then annually thereafter, a new or rehabilitated well for domestic use is placed into service, samples shall be collected and analyzed for chemical and bacteriological constituents and the results filed with the director. The director shall specify which chemical and bacteriological constituents are to be sampled and analyzed and specify the method of analysis, At a minimum all such wells shall meet state standards for large systems as defined by the California Code of Regulations, Title 22, as amended.

2. Samples for water quality analyses shall be collected from the discharge line before the storage tank.

3. Water samples shall be collected by persons trained and knowledgeable in the sampling procedures and chain-of-custody requirement for the constituents being analyzed.

4. Analysis of water samples shall be performed by a laboratory which is certified by the State Department of Health to perform the method of analysis specified by the director.

(Ord. 1754 § 1, 1990).

A. All abandoned wells, exploration holes or test wells, as defined by DWR Bulletin 74-81 as revised in 1988 or the latest revision, shall be destroyed in such a manner that they will not produce water or act as a conduit for mixing or otherwise transferring of water between permeable zones or aquifers, and will not be a hazard to the safety and well being of people or animals.

B. Materials used to fill a well shall have a low permeability. Materials shall meet the material standards prescribed in DWR Bulletin 74-81 as revised in 1988, and DWR Bulletin 74-88 or the latest revision.

C. Wells penetrating the Corcoran Clay shall be destroyed in a manner that ensures a seal is placed across the Corcoran Clay. If necessary, the casing shall be perforated for an interval of not less than ten feet and sealing material forced under pressure into the annular space.

D. Wells penetrating deeper than three hundred feet shall be destroyed in a manner that ensures a seal is placed across the three hundred foot clay. If necessary, the casing shall be perforated for an interval of not less than ten feet and sealing material forced under pressure into the annular space.

E. Wells without an upper annular seal equal to or greater than that set forth in Table 3 shall perforate the casing at a depth equal to Table 3 and inject sealing material under pressure into the annular space.

F. In areas where ground water pollution is known, the director may prescribe special methods for well destruction to prevent the migration of pollutants.

G. Any well, exploratory hole or test hole which is abandoned, out of service, or otherwise left unattended shall have a temporary cover over the well or hold opening which prevents the introduction of undesirable material into the well or hole, and ensures public safety. The cover shall be secured in such a manner that it cannot be removed except with the aid of equipment or through the use of tools.

H. The owner or permittee of any well, exploratory hole or test hole which is abandoned, out of service, or otherwise left unattended for a period greater than ninety days shall file with the director a letter of intent which provides the reason(s) for not properly destroying the well, exploratory hole or test hole as required by this chapter and which specifies the time when the well, exploratory hole, or test hole will be completed, put back in service, or destroyed as required in this chapter.

(Ord. 1754 § 1, 1990).