7 Del. Admin. Code § 7301-5.0

Current through Register Vol. 28, No. 5, November 1, 2024

Section 7301-5.0 - Well Construction Standards

5.1 Siting Criteria

5.1.1 All wells, except for monitor, recovery, dewatering, observation wells, and soil borings, shall be sited to achieve maximum separation distance along the entire well, but no less than the distances listed below:

5.1.1.1 100 feet from identifiable potential or existing sources of contamination with the exception of public wells. Exceptions to these requirements for all wells other than public wells are addressed in subsections 5.1 .1.2, 5.1.1.3, 5.1.1.4, 5.1.1.5, 5.1.1.6, and 5.1.1.8. Public wells shall have a minimum separation distance of 150 feet except as addressed in subsections 5.1 .1.5, 5.1.1.6, and 5.1.1.7.

5.1.1.2 50 feet from identifiable potential or existing sources of contamination for heat pump recharge, heat pump closed loop, and heat pump direct exchange wells pursuant to subsections 6.4 .2 and 6.5.1.

5.1.1.3 50 feet from any boundary of an Agricultural Lands Preservation District (as defined in 3 Del.C. Chapter 9) for any parcel, lot, or subdivision. Wells on parcels, lots, or subdivisions created or recorded prior to April 6, 1997 are exempt. The Department requires that all wells be placed the maximum distance possible from lands where federally regulated chemicals have been applied. Pesticides that have been applied in accordance with their respective pesticide product label and are not associated with any known contamination are exempt.

5.1.1.4 100 feet from the absorption facility, 50 feet from septic tanks, diversion valves or boxes, dosing chambers, holding tanks, or grease, except as allowed by subsection 5.1 .2.

5.1.1.5 50 feet from any underground sewer forced main or gravity sewer lines but no less than ten feet if the well is constructed in a confined aquifer or if cased and grouted to a minimum of 100 feet below ground surface except public wells. Public wells shall be located the maximum distance possible allowed by the well site, but no less than 75 feet from an underground sewer forced main or gravity sewer lines. The Department may approve a lesser distance on a case by case basis for public well sites provided the well can be screened in a confined aquifer or can be cased and grouted at least 100 feet below land surface. Sewer laterals are not to be interpreted as forced main or gravity sewer lines.

5.1.1.6 50 feet from the absorption facility of a residential septic system that has been decommissioned as documented by the Department.

5.1.1.7 10 feet from a property line to allow access to the well without encroaching on adjoining properties except as required in subsection 5.1 .1.8. All wells may be constructed less than 10 feet from a property line if approved by the Department for the purpose of maximizing other horizontal separation distances as required by this Section and avoiding public utilities. The applicant shall provide a notarized form provided by the Department and signed by the property owner that documents the reason(s) for the request.

5.1.1.8 150 feet within the outer most property lines of the housing development for public wells within a housing development recorded on or after April 6, 1997.

5.1.2 When any well, with the exception of public wells, cannot be located at the separation distance pursuant to subsection 5.1 .1.4 the following shall apply:

5.1.2.1 The separation distance shall be maximized but no less than 50 feet, provided the well is screened in a confined aquifer and pressure grouted from either the top of the gravel pack to the ground surface, or from the bottom of the casing to the ground surface (e.g., crystalline rock, consolidated open-borehole wells), except those wells specifically exempted in subsection 5.8 .7. In the event that a confined aquifer is not encountered within 150 feet of the ground surface, the well will be required to be cased and grouted to a minimum of 100 feet below the ground surface unless more specific aquifer confinement is required by the Department.

5.1.2.2 Where any public water supply well cannot satisfy the separation distance requirements of subsection 5.1 .1.1, the Department at its discretion may approve an alternate siting and/or construction method(s) and must follow the requirements of Section 12.0.

5.1.3 No wells shall be located within any dedicated State of Delaware right-of-way unless a utility or safety permit is submitted with the application.

5.1.4 The Department may approve a lesser separation distance for an agricultural well from an existing or potential source of contamination but the separation distance shall be maximized and shall be no less than 50 feet.

5.1.5 Water Supply Lines

5.1.5.1 Pressure lines shall be at least 10 feet from all identifiable potential or existing sources of contamination. Pressure lines that must cross a gravity sewer line shall be double cased at least 10 feet on either side of the intersection of the water line with the gravity sewer.

5.1.5.2 Suction lines shall be at least 50 feet from all identifiable potential or existing sources of contamination.

5.1.5.3 Double-cased suction lines shall be at least 10 feet from all identifiable potential or existing sources of contamination.

5.1.5.4 A well may not be constructed within or under any building other than a structure constructed specifically for the housing of the well and related equipment, unless otherwise approved in writing by the Department. Such structures shall be identified on the exterior with the permit number of the well contained therein.

5.1.6 All wells shall be located so as to be accessible for cleaning, treatment, repair, testing, inspection, and any other work.

5.1.7 All wells shall be protected from surface water run-off and flooding pursuant to subsection 5.11.

5.1.8 The Department may require special location and depth requirements for a proposed water supply well to minimize its exposure to identifiable potential or existing sources of contamination or interference with other water supply wells. The submission of drawdown data and capture zone analyses may also be required to justify the location and depth of the well.

5.1.9 Wells subject to flooding pursuant to subsection 6.2 .1 are subject to the additional siting requirements contained in subsection 6.2 .2.

5.2 Water Quality Protection During Well Construction

5.2.1 During well construction of the well, the well and any aquifers shall be protected against contamination.

5.2.2 Whenever construction stops prior to well completion, the open annular space or open borehole shall be covered and protected from surface water drainage. The well casing shall be capped in accordance with the requirements of subsection 5.11.

5.2.3 Whenever contamination is detected during drilling, and the contamination was not anticipated by the Department and addressed in the permit conditions, the well driller shall cease work and notify the Department at (800) 662-8802. Drilling may commence upon approval by the Department.

5.2.4 If contaminants are encountered during drilling, the well driller shall decontaminate the drilling equipment to prevent the transfer of contaminants into uncontaminated aquifers or from the site.

5.3 Water and Wells for Well Construction

5.3.1 Water for well construction from sources other than those listed below is prohibited:

5.3.1.1 A public water supply system meeting the requirements of the Delaware Regulations Governing Public Drinking Water Systems.

5.3.1.2 Any other potable water supply.

5.3.1.3 Other non-potable water supply wells such as irrigation or construction wells.

5.3.2 Water used for well construction shall be disinfected as follows:

5.3.2.1 Water from a potable source shall be maintained with a free chlorine residual of one milligram per liter (mg/L).

5.3.2.2 Water from a non-potable well shall be disinfected with one pound of calcium hypochlorite per 1,000 gallons of water. At least 30 minutes contact time shall elapse between addition of the disinfectant and use of the water. Sodium hypochlorite in the form of laundry bleach (5.25 percent available chlorine) may be used in lieu of calcium hypochlorite. One and seven tenths (1.7) gallons of laundry bleach are equivalent to one pound of dry calcium hypochlorite.

5.3.3 Well Construction Wells

5.3.3.1 The Department may issue a permit for a construction well to supply water for a new well installation. The application for a construction well should be submitted in conjunction with the application for a new well.

5.3.3.2 All construction wells shall be sealed pursuant to Section 10.0 prior to the demobilization of the drill rig.

5.4 Drilling Fluids

5.4.1 Drilling fluids shall consist of water-based or air-based fluids containing only additives manufactured for water well drilling.

5.4.1.1 If rapid loss of drilling fluid occurs, clean fill material such as sand, gravel, crushed stone, or drilling fluid additives manufactured for lost circulation may be used in the zone or zones where the loss is occurring.

5.4.2 The Department may set drilling fluid specifications for fluid viscosity and specific gravity. The Department may require that a report of drilling fluid characteristics be submitted with the completion report.

5.4.3 The use of polymers is permitted to increase viscosity and filtration control in drilling fluids.

5.5 Well Casing

5.5.1 Well casing shall be strong enough to resist the forces imposed on it during and after installation, following applicable specifications established by the American Petroleum Institute, American National Standards Institute, and the American Society for Testing and Materials.

5.5.2 Casing must not cause the delivered water to be toxic or violate state or federal drinking water standards, following the specifications established by the National Sanitation Foundation.

5.5.3 Casing other than polyvinyl chloride (PVC) or steel shall only be used with the written approval of the Department.

5.5.4 Polyvinyl chloride (PVC) casing shall be a minimum of Schedule 40 unless otherwise approved by the Department.

5.5.5 For wells with a diameter greater than six inches, the water well contractor shall account for conditions such as installation depth that may require heavier-weight well casing.

5.5.6 Steel casing shall be used for wells constructed in crystalline rocks.

5.5.7 Steel casing shall be a minimum of at least Schedule 40 unless otherwise approved by the Department.

5.5.8 The Department may require that casing used for water supply wells be at least four inches in diameter. The Department may require that casing used for public supply wells be at least six inches in diameter.

5.5.9 Well Casing Lengths

5.5.9.1 Overall casing length shall be no less than 20 feet. Monitor, observation, recovery, wick drains, dewatering, and large diameter bored wells are excluded from this requirement. Required casing heights above ground surface are specified in subsection 5.11.

5.5.9.2 Wells (except monitor, observation, dewatering, and recovery wells) located on tax parcels less than one-half acre in size and where an on-site wastewater treatment and disposal system is or will be utilized, shall be cased to a minimum depth of 42 feet below land surface.

5.5.9.3 Wells completed in a confined aquifer shall be cased to the top of or into the source aquifer.

5.5.9.4 Wells sited pursuant to subsection 5.1 .1.6 shall be cased to a minimum depth of no less than 42 feet below land surface.

5.5.10 Other Well Casing Requirements

5.5.10.1 Joints for all well casing shall be water tight and joined in accordance with the manufacturer's recommendations. Joints for steel well casing may be electrically welded or threaded. Joints for polyvinyl chloride (PVC) well casings shall be solvent welded or threaded. All couplings and solvents shall meet ANSI/NSF Standard 14, ASTM F480 or similar requirements.

5.5.10.2 Casing must not be cut off below ground level pursuant to subsection 5.11 .8, or

5.5.10.2.1 To install a pitless unit or pitless adapter, or

5.5.10.2.2 To install a standard plumbing "Tee", or

5.5.10.2.3 To install an outer casing to terminate just below a pitless adapter or standard plumbing "Tee" connection, that is on the inner casing, or

5.5.10.2.4 For sealing purposes.

5.5.10.3 Where steel well casing is required, the casing shall be equipped with a drive shoe that shall be firmly seated by driving it into the rock prior to continuation of drilling or grouting.

5.6 Well Screens

5.6.1 All wells that obtain water from unconsolidated aquifers shall be equipped with a well screen that will limit the entrance of sediments.

5.6.2 Wells finished in consolidated aquifers are not required to be screened.

5.6.3 Well screens shall have sufficient structural strength appropriate for installation.

5.6.4 The screen shall be sized to meet the screen manufacturer's specifications.

5.6.5 Only commercially manufactured well screens, constructed of materials resistant to damage by chemical action of groundwater or cleaning agents, shall be used in the construction of a well, unless otherwise approved by the Department.

5.6.6 Lead packers and lead swedges are prohibited.

5.6.7 The bottom of the well screen shall be closed.

5.6.8 Aquifer interconnection, as determined by the Department, is prohibited.

5.7 Gravel Packed Wells

5.7.1 Gravel shall be free of foreign matter, well sorted, and properly sized. The gravel shall be disinfected as it is placed into the well annulus in one continuous operation.

5.7.2 Bulk gravel shall be covered and stored to prevent direct contact with the ground.

5.7.3 The placement of gravel into the annulus shall completely encase the well screen and prevent grout from entering the screen after settlement. The Department may require gravel placement with a tremie pipe, as needed.

5.7.4 Placement of gravel that causes interconnection of aquifers, as determined by the Department, is prohibited.

5.7.5 Gravel must not extend more than 10 feet above the top of the screen in single cased wells unless otherwise approved by the Department.

5.7.6 Gravel may be used to fill the annulus of geothermal closed loop wells from the bottom of the borehole to the bottom of the overburden only in the Piedmont physiographic province.

5.8 Well Grouting

5.8.1 All wells shall be grouted from the top of the gravel pack to the ground surface unless specifically exempted in subsection 5.8 .7 or otherwise approved by the Department.

5.8.2 The annulus shall be a minimum of 1.5 inches wide (diameter of bore hole = outside diameter of casing plus three inches). Wells used for the purpose of groundwater monitoring or observation shall have a minimum annulus of 0.50 inches wide (diameter of borehole equals the outside diameter of the casing plus one inch).

5.8.3 All wells shall be grouted within 24 hours after the casing has been set.

5.8.4 Wells 40 feet or less in depth that are constructed in unconfined aquifers, may be grouted by pouring chipped or pelletized bentonite into the annulus. For wells deeper than 40 feet in depth, the annulus shall be pressure grouted from top of the gravel pack to ground surface. For exceptions, see subsection 5.8 .13.2.

5.8.5 For single-cased wells constructed in confined aquifers, the casing shall be pressure grouted from the top of the gravel pack to ground surface.

5.8.6 Geothermal closed loop and direct exchange wells shall be pressure grouted from the bottom of the bore hole to the ground surface.

5.8.7 Wells with casing depths of 20 feet or less are not required to be grouted, except monitor, observation, recovery wells, and wick drains less than 20 feet in depth may be required to be grouted.

5.8.8 The use of drill cuttings between the gravel pack and the required grout depth for domestic, public, and heat pump supply (potable) is prohibited.

5.8.9 The water well contractor may be required to notify the Department in advance of grouting. If the Department has scheduled a grouting inspection, the driller is not permitted to proceed with grouting unless otherwise instructed by the Department.

5.8.10 Cement grout must be allowed to cure for a minimum of 24 hours from the completion of grouting before well construction activity, including development, can be resumed.

5.8.11 The Department may specify additional conditions pertaining to the grouting of any well.

5.8.12 Grouting

5.8.12.1 Cement may be neat Portland or quick setting (hi-early) cement in a ratio of no more than six gallons of water per 94 pound bag of cement. Sodium based bentonite may be added to the cement grout in an amount not to exceed five pounds per 94 pound bag of cement.

5.8.12.2 Bentonite grout is a sodium based bentonite with a ratio of not less than two pounds of bentonite per gallon of water. Bentonite clay without additives shall not be used where it comes in contact with groundwater with a pH less than five or having a total dissolved solids content greater than 1,000 milligrams per liter (mg/L) without Department approval.

5.8.12.3 Thermally enhanced bentonite grout is a sodium-based bentonite silica sand mixture with a ratio of not less than 1.5 pounds of bentonite per gallon of water containing no more than 300 pounds of sand per 50 pounds of bentonite. Sand shall be "000" well gravel or range between 50 and 70 mesh containing a minimum of 95% silica having a uniformity coefficient not greater than 1.7.

5.8.12.4 If rapid loss of grout material occurs during emplacement, clean fill material such as sand, gravel, crushed stone, or cement additives manufactured for lost circulation may be used in the zone where the loss is occurring.

5.8.12.5 Use of polymers is permitted to slow the hydration of bentonite.

5.8.12.6 All water used for grouting shall be treated to achieve a minimum pH of 8.0 with soda ash (sodium carbonate (Na2C03)) or other industry recognized products.

5.8.13 Standards for Grouting

5.8.13.1 Well grouting shall be performed to provide a water tight seal that prevents fluid migration into the annulus of the well.

5.8.13.2 All single-cased wells shall be grouted from either the top of the gravel pack to the ground surface, or from the bottom of the casing to the ground surface (e.g., crystalline rock, consolidated open-borehole wells), except those wells specifically exempted in subsection 5.8 .7.

5.8.13.3 If the annular space cannot be grouted in accordance with these Regulations, the well shall be sealed pursuant to Section 10.

5.8.13.4 The top of grout shall be at the base of the well's discharge line for wells equipped with pitless adapters, pitless well unit, or plumbing "Tees".

5.8.13.5 Grouting requirements for multiple-cased wells shall be determined on an individual basis.

5.9 Well Development

5.9.1 Development shall be performed until formation cuttings, mud, and drilling fluids or other additives are completely removed from the well and surrounding aquifer.

5.9.2 All potable wells shall be developed such that the water meets the following requirements:

5.9.2.1 Contains less than one milligram of sand or larger particles per liter of water (particles with a diameter larger than 0.0625 millimeters);

5.9.2.2 Has a turbidity of less than 10 NTU (Nephelometric Turbidity Units), except when the turbidity is due to the oxidation of naturally occurring dissolved iron or manganese.

5.10 Pitless Well Adapters, Pitless Well Units, and Plumbing "Tees"

5.10.1 A pitless well adapter or pitless well unit shall be installed on all potable wells having a submersible pump or deep well ejector jet pump.

5.10.2 For suction lift systems where the well casing is used as a suction line and for heat pump recharge wells, a standard plumbing "Tee" connector and extension pipe with cap may be used in place of a pitless well adapter or pitless well unit, providing the extension meets the requirements pursuant to subsection 5.11.

5.10.3 All pitless well adapters or pitless well units shall be of a type approved by the National Sanitation Foundation, the Water Systems Council, or the Department.

5.10.4 Connections of the pitless well adapter, pitless well unit, or plumbing "Tee" to the well casing and lateral connections of piping shall be watertight.

5.10.5 A pitless well adapter, pitless well unit or plumbing "Tee" shall be installed in conformance with depth of water service piping requirements pursuant to subsection 3.21.

5.11 Well Caps and Well Heads

5.11.1 For flood-prone wells, the top of the well head or pitless well unit shall be no less than 24 inches above ground surface, or the highest known flood level, whichever is greater.

5.11.2 For domestic and agricultural wells, the top of the well head, or pitless well unit shall be no less than eight inches above the finished ground surface or pump house floor unless otherwise approved by the Department.

5.11.3 For monitor and observation wells, the top of the well head, except as provided by subsection 5.11 .6, shall be no less than 24 inches above the finished ground surface except as required by subsection 6.1 .3. The casing shall be protected from entry by contaminants, vandalism, accidental damage, etc. The required protection devices are:

5.11.3.1 A locking well cap.

5.11.3.2 For PVC casing - a concentric, protective steel casing firmly set in concrete. The Department may waive this requirement for specific projects (such as, small on-site wastewater treatment and disposal systems).

5.11.4 For public, irrigation, and industrial wells, the top of the well head or pitless well unit shall be no less than 18 inches above the finished ground surface.

5.11.5 For wells and well points used for dewatering, the top of the well head or takeout shall be no less than 12 inches above the finished ground surface.

5.11.6 Monitor and observation wells may be terminated below finished ground surface upon approval by the Department.

5.11.7 The Department may require additional protective devices such as bollards in high traffic areas.

5.11.8 Well pits, pump pits and buried well seals are prohibited. Upon approval by the Department, potable wells may be terminated below finished ground surface if above grade completion is not feasible. The engineered design of the enclosure must be included with the application or submitted prior to modification of an existing well.

5.11.9 All wells shall be securely covered except during construction and testing. Caps shall be lockable or removable only with tools. If a cap cannot be used, an alternative method for securely covering the well shall be employed.

5.11.10 Any time an existing well is identified as not meeting the requirements of this Section, the well head shall be brought into compliance unless otherwise approved by the Department. Wells permitted prior to the effective date of these Regulations are exempt. The Department may impose these requirements upon the reclassification of any well.

5.12 Water Level Access Ports and Tubes

5.12.1 All wells with a pumping capacity greater than 50,000 gallons per day shall be constructed with an access port and tube.

5.12.2 All public wells that supply a community water system and all industrial wells shall have a capped access port and tube. A transducer may be installed in addition to the access port and tube.

5.12.3 If the pump motor is not installed directly over the well, the access port shall be located directly on top of the well.

5.12.4 If the pump motor is installed directly over the well, an access port pipe shall be installed through the pump base or outside the well casing at some accessible point below the base of the pump.

5.12.5 The access port and tube shall have a minimum inside diameter of three-quarters inch.

5.12.6 The access port shall be constructed to prevent the entrance of water, dust, insects, or other foreign material, and allow access for water level measurements.

5.12.7 The use of air line gauges for water level measurement is prohibited.

5.13 Meters, Pumping Equipment, and Vents

5.13.1 All wells with a design capacity greater than 50,000 gallons per day shall be permanently equipped with a meter or meters capable of acquiring instantaneous flow rate and totalized flow measurements accurate to within five percent of the actual flow rate, unless otherwise approved by the Department or pursuant to subsection 5.13 .2. Flow rate indicators may consist of any combination of test dials and direct reading indicators.

5.13.2 Irrigation wells and non-potable wells constructed and used for fire protection with a design capacity greater than 50,000 gallons per day shall be permanently equipped with an elapsed time meter, readable in hours or minutes, equipped on the well's drive engine or motor to measure actual hours of operation. If an irrigation well has been determined by the Department to be located in an area at risk for saltwater intrusion or where demands may exceed supplies, the Department may require the well to be permanently equipped with a meter or meters capable of acquiring instantaneous flow rate and totalized flow measurements accurate to within 5 percent of the actual flow rate.

5.13.3 All public and industrial wells shall be permanently equipped with a meter capable of acquiring instantaneous flow rate and totalized flow measurements accurate to within five percent of the actual flow rate, unless otherwise approved by the Department.

5.13.4 A backflow protection device shall be installed in a pumping system containing a well if the pumping system is connected to a treatment system, is used to convey wastewater, fertilizers, chemicals, or provides fire protection pursuant to subsection 6.3 .3.

5.13.5 Water systems that draw from more than one aquifer shall have a backflow prevention device on the discharge line of each well to prevent the introduction of water that is not native to the source aquifer.

5.13.6 The proposed withdrawal rate shall be consistent with the pump capacity, well design, and the intended use of the well.

5.13.7 Well vents shall be covered with corrosion-resistant mesh screen and down-turned to prevent the entrance of surface water, insects, or other foreign material.

5.13.8 Upon completion of installation, the driller or pump installer shall disinfect the well and pump in accordance with Section 7.0.

7 Del. Admin. Code § 7301-5.0

20 DE Reg. 180 (9/1/2016)<linebreak/> 20 DE Reg. 374 (11/1/2016) (Final)