40C-3.512. Well Construction Requirements

(1) In the construction of a well, reasonable caution shall be taken to maintain the work site so as to minimize the entrance of contaminants into the water resource. Materials used in construction shall be reasonably free of contamination. The requirements for construction of public supply wells can be found in Chapter 62-555, F.A.C.

(a) During construction, the water used to mix the drilling fluids must either maintain a minimum free chlorine residual of 10 mg/l or be supplied from a potable well or water supply. If the well or water supply is a known source of contamination or is within a known area of contamination, it shall not be used to provide water to construct the well.

(b) Disinfection of filter or gravel pack materials will follow guidelines found in AWWA Standard A100-84, Section 11.4, unless materials are obtained from a commercial source.

(c) Upon completion of construction, the well must be disinfected using a solution of water and available chlorine compounds providing a concentration not less than 50 mg/l. USEPA Manual of Well Construction Practices, EPA-570/9-75-001, Section 54.001-000-000, provides a tabular determination of disinfectant per 100 feet of well depth to achieve the required residual.

(d) For non-potable (non-domestic) wells the contractor may elect either to maintain a minimum of 10 mg/l free chlorine in the water used to mix the drilling fluid during construction of the well or to disinfect the completed well with a solution of water and available chlorine compounds at a concentration of no less than 50 mg/l. Development should occur prior to disinfection so the well may be cleared of chlorine by flushing the entire water system prior to use. The disinfecting agent shall be left in the well for a period of at least twelve hours and then pumped to clear the disinfecting agent taking care to minimize potential damage to the environment. Free-flowing artesian wells will be disinfected by using either potable water or maintaining a minimum free chlorine residual of 10 mg/l in water used to mix the drilling fluid until the free flowing water zone is reached.

(2) For wells which penetrate multiple aquifers or water bearing zones the well shall be completed so as to prevent cross-contamination. If significantly different water quality exists between these aquifers or water bearing zones, leakage of water from one aquifer or water bearing zone to another must be prevented.

(3) For wells finished into unconsolidated aquifers, continuous casing shall extend from the well’s terminus to the well screen. The well screen shall be attached to the casing with a watertight seal. The lower terminus of the well screen shall be sealed to prevent the entrance of particulate materials. A tailpipe is allowed if affixed to the screen with a watertight seal and plugged at its lower terminus.

(4) For wells completed into consolidated aquifers, a continuous casing shall extend from the upper terminus and be seated into:

(a) The producing aquifer, or

(b) Into a consolidated stratum within a continuous non-caving confining unit immediately overlying the aquifer from which the water is to be withdrawn.

(5) For wells completed into consolidated aquifers which are constructed using telescoping casings the following practices will be acceptable:

(a) Two casings may be telescoped and sealed with a packer and one casing centralizer when paragraph 40C-3.517(4)(c), F.A.C., construction methods are used. Two centralizers shall be used when the internal casing is grouted. A minimum of 5 feet overlap is required for nonpublic supply wells which are less than 6'' in diameter. A minimum ten feet of overlap is required for nonpublic supply wells a minimum of 6'' or more in diameter. The minimum required overlap for public supply wells remains 20 feet, as set forth in Chapter 62-555, F.A.C.

(b) The annular space between telescoped casings shall meet minimum grouting standards in subsections 40C-3.517(2) and (3), F.A.C.

(6) The upper terminus of the well to which the well head is affixed shall extend either to land surface or to finished grade, whichever is higher, or where a potential physical or traffic hazard exists, the well head must:

(a) Be placed in an appropriate enclosure terminating at land surface or finished grade, whichever is higher, that allows vertical access to the casing and proper drainage, and that protects the well head from the entrance of contaminants;

(b) Be completed to a point 18 inches or less below land surface or finished grade, whichever is higher. There must be a concrete marker 10 inches in diameter and 4 inches thick with an inserted metal disk clearly marked as required in subsection 40C-3.461(2), F.A.C., placed at land surface or finished grade. The upper terminus of the casing shall be sealed in a manner which prevents the entrance of contaminants into the well; or

(c) Be completed to a point 18 inches or less below land surface or finished grade, whichever is higher. A tee and nipple must be affixed so that the casing extends to land surface or finished grade while permitting a below grade water line to extend to a designated location remote to the water well. This subsection does not apply to public supply wells regulated under Chapter 62-555, F.A.C.

(7) For wells constructed in those areas of the District in which chert occurs, the well casing shall extend from its upper terminus to:

(a) A point below the dry season water level of the producing aquifer, or

(b) A point firmly seated in chert overlying a stratum of limestone if the underlying limestone does not produce a quantity of particulate materials after development that will clog a filter or decrease the ability of the well to produce water.

(8) Water wells constructed using Bentonite grouts shall meet all the following requirements:

(a) The casing seat must be clean allowing the casing to set at the total depth bored in a hole reasonably free of drill cuttings;

(b) A formation boot or Portland Cement plug must be installed at the casing seat;

(c) Portland Cement must be placed in the upper three feet of the annular space to prevent deterioration of or damage to the Bentonite seal; and

(d) Bentonite grout may be used only on domestic, irrigation, water source or ground source heat pump installations or well abandonments with a nominal casing diameter of four inches or less. Use of Bentonite grout is not allowed on public supply wells or where artesian flow occurs or in any identified contamination sites.

In all circumstances the requirements of subsection 40C-3.512(2), F.A.C., must be met. All caving zones within the well must be cased or lined when caving occurs below the casing seat. No casing may be seated into an unconsolidated unit above the producing aquifer.

(9) In addition to the other applicable standards contained in this chapter, wells constructed in the Picketville Landfill Special Construction Criteria Area shall meet the following minimum criteria:

(a) For Zone A, of new wells which are completed into the surficial aquifer system, including the upper sand and lower shallow-rock zone, to a depth of 110 feet below land surface or less than five feet into the intermediate aquifer system are prohibited. This prohibition of new wells does not apply to moniter wells, recovery wells or piezometers which may be used for assessment of clean up of contamination sites.

(b) New wells may be completed into the intermediate aquifer system producing zone at least 300' below ground surface, or into the Floridan aquifer system.

(c) New wells penetrating the intermediate system or Floridan aquifer producing zones shall be constructed in the following manner:

1. A minimum 6-inch exterior casing shall be installed and grouted to no less than five feet into the top of the confining unit immediately below the shallow rock zone of the surficial aquifer system.

2. A minimum 2-inch interior casing within the 6-inch casing shall be installed and grouted to the producing zone. For wells constructed into the intermediate system, the intermediate aquifer shall be screened unless the entire producing zone is consolidated.

3. The top casing diameters shall allow a minimum nominal grouting annulus of two inches.

4. For telescoped wells constructed in reliance on the criteria of paragraph 40C-3.517(4)(c), F.A.C., in addition to the overlap created by the telescope, a fifty foot minimum length of internal casing shall be grouted below the telescoped joint.

5. The internal casing of all wells shall be completed to a minimum of twelve inches above grade.

(d) In Zone A, each existing well in the surficial aquifer system shall be abandoned when public supply lines are installed adjacent to the property served by the well.

(e) All Chapter 62-524, F.A.C., construction standards shall be met in both Zone A and Zone B.

(10) In addition to the other applicable standards contained in this chapter, wells constructed in the Fairbanks Special Construction Criteria Area shall meet the following minimum criteria:

(a) In Zone A, new wells which are completed into the Surficial Aquifer System or into the Intermediate Aquifer System, are prohibited. This prohibition of new wells does not apply to monitor wells, recovery wells or piezometers which may be used for assessment or cleanup of contaminated sites.

(b) In Zone A, new wells penetrating the Floridan Aquifer producing zones must be constructed in the following manner:

1. A minimum 12-inch exterior casing shall be installed and grouted to no less than five feet into the upper confining unit of the intermediate aquifer system.

2. A minimum 8-inch interior casing within the 12-inch casing shall be installed and grouted to no less than five feet into the lower confining unit of the Intermediate Aquifer System.

3. A maximum 4-inch permanent water bearing casing within the 8-inch casing must be installed into the Floridan Aquifer System to a depth of at least one full casing lengths below the formation contact.

4. The casing diameters shall allow a minimum nominal grouting annulus of two inches.

5. The internal casing of all wells shall be completed to a minimum of twelve inches above grade.

6. In Zone A, all new wells shall be logged using gamma, caliper or video equipment.

(c) In Zone A, each existing well in the Surficial and Intermediate Aquifer System shall be abandoned when public supply lines are installed adjacent to the property served by the well.

(d) In Zone A, water quality samples must be taken and analyzed by Environmental Protection Agency methods 601, 602 and 610 where the casing is set in the Floridan Aquifer System. Water quality results from the Floridan Aquifer System shall reveal no contaminants before well construction is completed. In the event that water quality testing indicates that there is contamination in the groundwater, the well shall be plugged and abandoned pursuant to Chapter 40C-3, F.A.C.

(e) In Zone B, new wells shall be logged, sampled and analyzed by Environmental Protection Agency methods 601, 602 and 610 for groundwater contaminants.

(f) Prior to any well construction in the Fairbanks Special Construction Criteria Area identified in subsection 40C-3.502(3), F.A.C., all persons shall obtain a well construction permit from the St. Johns River Water Management District. Construction standards as provided in Chapter 62-524, F.A.C., shall be applicable to all well construction in the Fairbanks Special Construction Criteria Area.

(g) In Zone A and Zone B, all unused wells must be capped and locked or plugged and abandoned. In Zone A, wells connecting separate aquifer systems must be plugged and abandoned.

Rulemaking Authority 373.044, 373.309 FS. Law Implemented 373.306, 373.308, 373.113 FS. History–New 10-14-84, Amended 4-23-85, Formerly 40C-3.512, 40C-3.0512, Amended 9-17-89, 9-16-93, 8-30-94, 3-5-95.