12 Va. Admin. Code § 5-630-410

Current through Register Vol. 41, No. 8, December 2, 2024

Section 12VAC5-630-410 - Construction; general

A. Private wells shall be constructed using the criteria described in this section. The water well system provider shall provide advance notification regarding the initiation of well construction to the district or local health department to allow department personnel the opportunity to observe well construction. The water well systems provider may construct the well as conditions warrant and shall be under no obligation to delay construction activities pending arrival of district or local health department personnel.

B. Well bore.

1. The method of advancement of the well bore in which the private well is constructed shall be determined by the water well systems provider relative to local geologic and aquifer conditions.

2. When the construction permit designates a well site, the well bore shall be placed at the well site. When the construction permit designates a well area, the well bore may be placed anywhere within the well area. If a well bore advanced within a well area must be discontinued for any reason, the well bore shall be abandoned in accordance with 12VAC5-630-450 and a new well bore may be undertaken within the well area.

3. Other land disturbance associated with well construction, such as grading and mud pit construction, is not limited to the well area.

4. With the exception of driven wells, the well bore shall be large enough to accommodate the well casing and screen with sufficient annular space on all sides of the casing in the interval to be grouted to freely accommodate a tremie pipe or sounding tube.

5. Drilling fluids used to stabilize the well bore shall be maintained within limits that will allow their complete removal from the water produced from the well, and shall not damage the capacity, efficiency, and quality of the well.

6. Representative samples of formation materials shall be collected during well bore advancement with sufficient frequency to allow for preparation of the driller's log (uniform water well completion report) of the type of rock, sediment, or soil encountered.

C. Casing.

1. The casing shall maintain the well bore by preventing its walls from collapsing, provide a channel for the conveyance of water, and protect the quality of the water withdrawn from the well. The thickness of the casing shall be sufficient to resist the force imposed during installation and which can be anticipated after installation.

2. Class IIIA and IVA wells shall be cased to a depth of at least 100 feet.

3. Class IIIB and IVB wells shall be cased to a depth of at least 50 feet.

4. Except as provided in subdivisions a through e below, Class IIIC and IVC wells shall be cased to a minimum depth of 20 feet or terminated not less than one foot in bedrock when bedrock is encountered at a depth less than 20 feet.

a. When in collapsing material, the casing shall terminate in the aquifer but in no instance be less than 20 feet.

b. Where an aquifer is encountered at less than 20 feet, Class IVC wells may be cased to within one foot of the water bearing strata. In the instance of Class IV wells the intent of this chapter is to protect groundwater quality, and not to ensure a potable water supply.

c. Alternate casing depths may be accepted for bored wells when the only aquifer lies between 11 and 20 feet provided the casing is placed within one foot of the aquifer and must not be less than 10 feet in depth from the ground surface.

d. Class IIIC driven wells shall be cased to the water bearing strata; however, in no case less than 10 feet. No minimum casing requirements apply to Class IVC driven wells except that in order to protect groundwater they shall be capable of meeting the minimum grouting requirements as described in subdivision F 5 e of this section.

e. Closed-loop ground-source heat pump wells do not have to be cased.

5. When PVC casing is terminated in bedrock, the well casing shall be sealed using a mechanical seal or packer.

6. Extension of casing above ground surface. Private well casings shall be extended at least 12 inches above ground or at least 12 inches above a concrete floor in a well house with a gravity flow drain. The following wells are exempted from this requirement; however, their location shall be permanently marked for easy location in the future:

a. Drilled shallow well suction pump systems that will not operate unless a vacuum is maintained. The casings for these wells are also the suction lines through which water is drawn.

b. Deep well ejector pump systems that utilize a casing adaptor and must maintain a vacuum to operate.

c. Closed-loop ground-source heat pump wells.

d. Heat pump return wells that are completely sealed.

7. The casing shall be centered in the well bore the entire depth of the well in order to provide for even distribution of filter pack and grout in the annular space.

8. Joints shall be compatible with the casing material, specific to the task, and be watertight under normal operating conditions, with watertight joints above the screened interval.

9. Casing straightness and alignment:

a. Casing in all private wells shall be sufficiently straight that it will not interfere with the installation and operation of a pump suitable for the intended purpose of the well.

b. For casing intended to accommodate a line shaft turbine pump, the maximum allowable horizontal deviation of the well from the vertical shall not exceed 2/3 times the smallest inside diameter per 100 feet of that part of the well being tested to the depth of the anticipated pump installation.

D. Screens.

1. The screen shall allow passage of water from the aquifer and provide sufficient tensile, collapse, and compression strength to withstand the physical loading it will be exposed to during installation, completion, development, and operational conditions. When used for the prevention of entry of foreign materials, screens shall be free of rough edges, irregularities, or other defects. A positive watertight seal between the screen and the casing shall be provided when appropriate.

2. Screen length, diameter, and slot size shall be determined based on field examination of representative samples of formation material collected during advancement of the well bore, and may be supplemented by sieve analysis of materials in the water bearing zone or geophysical logging of the well bore.

3. Joints between (i) casing and screen and (ii) screen and screen shall meet the requirements of subdivision C 8 of this section.

4. The bottom of the screen, or of the deepest screen in the case of multiple screens, shall be configured to reduce the possibility of native formation or well construction material heaving up into the screened interval. A closed bottom may not be required for screens installed in some formation materials.

5. The screen shall be centered in the well bore.

E. Filter pack.

1. When a filter pack is required, the filter pack material used shall be determined based on field examination of representative samples of the water bearing formation in the withdrawal interval, and may be supplemented by sieve analysis. The filter pack shall be placed in the annular space by a method that prevents bridging and creates uniform distribution.

2. The filter pack shall extend above the top of the screened interval to a thickness sufficient to compensate for settling that may occur during development and operation of the well.

3. Filter pack material may be used with a screen as a formation stabilizer when water is withdrawn from a poorly consolidated rock subject to disintegration and caving when the well is pumped. Formation stabilizer shall be at least as coarse as the formation native material.

F. Grouting.

1. General. Private wells shall be grouted.

2. Purpose. The annular space between the casing and well bore is one of the principal avenues through which undesirable water and contaminants may gain access to a well. The goal of grouting a well is to preclude the entrance of undesirable water and contaminants. Therefore, the annular space shall be filled with a neat cement grout, a mixture of bentonite and neat cement or bentonite clay grout specifically approved by the manufacturer for use as a grouting material.

3. Based on the well casing material and native geology, grout material shall be selected to minimize potential for spidering, cracking, or separation of grout from the well casing.

4. When an open well bore has been drilled below the depth to which the casing is to be grouted, the lower part of the hole must be backfilled, or a packer must be set in the hole to retain the slurry at the desired depth. Backfilling the hole with gravel and capping with sand is an acceptable practice. Material ordinarily sold as plaster or mortar sand is satisfactory; more than half the sand should be of grain sizes between 0.012 inches and 0.024 inches.

5. Depth.

a. Class IIIA and Class IVA wells shall be grouted to a minimum depth of 20 feet.

b. Class IIIB and Class IVB wells shall be grouted to a minimum depth of 50 feet.

c. Class IIIC and Class IVC wells shall be grouted to a minimum depth of 20 feet when the casing depth is equal to or greater than 20 feet. When the casing depth is less than 20 feet, the casing shall be grouted in accordance with this subsection, from the lower terminus of the casing to the surface.

d. Alternate grouting depths may be accepted for bored wells when the only aquifer suitable for a private well lies between 11 and 20 feet provided the grouting shall terminate at least one foot above the aquifer but must not be less than 10 feet in depth from the ground surface.

e. Driven wells shall be grouted to a minimum depth of five feet by excavating an oversize hole at least four inches in diameter larger than the casing and placing an approved grout mixture into the annular space.

6. Installation. Grout shall be installed by means of one of the following methods.

a. Placement using a grout pump or tremie pipe from the bottom of the annular space upward in one operation until the annular space is filled.

b. Pouring of grout is acceptable for bored wells when the grouting depth does not exceed 20 feet provided there is a minimum of a three-inch annular space and the annular space is free of standing water.

c. Bentonite chips or pellets are acceptable for bored wells when the grouting depth does not exceed 20 feet provided the annular space is at least four inches greater than the outside diameter of the casing or coupling and the casing and the annular space is free of standing water. Bentonite chips or pellets shall be placed via a tremie pipe having an interior diameter at least four times the size of the pellet or chip.

d. Placement of bentonite chips by free fall shall only occur within five feet of the ground surface.

7. Surface completion of grout. Grout shall be brought to the ground surface and flared to provide a one-foot radius around the casing at least six inches thick. However, whenever pitless adapters are used, the grout shall terminate at the base of the pitless adapter. When an outer casing is necessary to construct a new well, where possible, the outer casing shall be pulled simultaneously with the grouting operation.

G. Additional casing and grouting. When a well is to be constructed within 100 feet of a subsurface sewage disposal system, which has been or is proposed to be installed at a depth greater than five feet below the ground surface, the casing and grouting of the water well shall be increased to maintain at least a 15-foot vertical separation between the trench bottom and the lower terminus of the casing and grouting.

H. Well head.

1. General. No open wells or well heads or unprotected openings into the interior of the well shall be permitted. Prior to the water well systems provider leaving the well construction site, the owner shall have the water well systems provider protect the well bore by installing a cover adequate to prevent accidental contamination.

2. Mechanical well seals. Mechanical well seals (either sanitary well seals or pitless adapters) shall be used on Class III and Class IV wells and shall be watertight and airtight, except as provided in 12VAC5-630-410 I 4.

3. Other. Wells greater than eight inches in diameter shall be provided with a watertight overlapping (shoebox) type cover, constructed of reinforced concrete or steel.

I. Appurtenances passing through casing.

1. General. Openings through well casings shall be provided with a positive water stop.

2. Pitless well adapters. When used, pitless units and pitless adaptors shall be attached to the casing in a manner that will make the connection watertight. If an access port is installed, it shall be watertight.

3. Sanitary well seals. When used, sanitary well seals shall be installed according to the manufacturer's recommendations. A one-piece top plate shall be used on a well that terminates outdoors.

4. Venting. Venting shall be provided in such a manner as to allow for the passage of air, but not water, insects, or foreign materials into the well.

J. Well development.

1. "Well development" means the act of repairing damage to the geologic formation from drilling procedures and increasing the porosity and permeability of the materials surrounding the intake portion of the well. It is accomplished by application of mechanical energy, chemicals, or both to (i) remove drilling fluids and formation damage caused by the well bore drilling and well completion processes; (ii) remove formation fines near the well bore to increase hydraulic conductivity and create a filter medium; (iii) establish optimal hydraulic contact between the well and the geologic formation (aquifer) supplying water; (iv) provide for an acceptable level of sand and turbidity; and (v) provide for an appropriate level of drawdown at the production pumping rate.

2. Private wells shall be developed. Disinfection required by 12VAC5-630-430 and water quality testing required by 12VAC5-630-431 shall not be conducted on a well prior to well development.

K. Well maintenance and repair.

1. Equipment and water or other materials used during hydraulic fracturing of bedrock wells shall comply with 12VAC5-630-400.

2. Private wells shall be disinfected per 12VAC5-630-430 following maintenance, redevelopment, or other activity requiring access to the interior of the casing of a completed well.

12 Va. Admin. Code § 5-630-410

Derived from VR355-34-100 §3.7, eff. April 1, 1992; Amended, Virginia Register Volume 41, Issue 04, eff. 11/6/2024.

Statutory Authority: §§ 32.1-12 and 32.1-176 of the Code of Virginia.