Code of Maine Rules › 06 - DEPARTMENT OF ENVIRONMENTAL PROTECTION › 096 - DEPARTMENT OF ENVIRONMENTAL PROTECTION - GENERAL › Chapter 405 - Solid Waste Management Rules: Water Quality Monitoring, Leachate Monitoring, and Waste Characterization › Section 096-405-5 - Standards for the Installation, Construction and Maintenance of Wells and Piezometers, and for the Advancement of Borings

Current through 2024-29, July 17, 2024
This section describes requirements for wells, piezometers
				  and borings for all types of monitoringand investigations at all types of
				  facilities.
A.
Construction of
				wells and piezometers.
Monitoring wells and piezometers must be
				installed in a manner that maintains the integrity of the bore hole. The design
				and construction of the well or piezometer directly affects the quality and
				representativeness of the samples collected. The following criteria must be
				followed during the construction of wells, piezometers and borings:
(1) Construction and installation of wells
				and piezometers must be appropriate to insure that ground water samples and
				head measurements characterize discrete hydrogeologic units; and to prevent
				leakage of ground water, surface water or contaminants along the well annulus.
				If leakage is detected it must be corrected or the well abandoned. Wells
				installed for the purpose of ground water sampling and analysis must be capable
				of producing samples low in turbidity;
(2) All ground water monitoring wells must be
				constructed of PVC well casing material. Monitoring well casing must have a
				minimum inside diameter of 2 inches. Wells constructed in unconsolidated
				material less than 100 feet in depth must be constructed using a minimum of
				schedule 40 PVC well casing;
(3)
				All casing must be constructed of flush threaded joints or threaded coupling
				joints. All joints must be fitted with an "O" ring or wrapped with Teflon tape.
				Solvent welded joints are not acceptable;
(4) Wells and piezometers may be placed
				individually or as clusters. Clusters consist of individual wells or
				piezometers at varying depths in close proximity, each installed in its own
				boring;
(5) Appropriate precautions
				must be taken during drilling and construction of wells and piezometers to
				avoid introducing contaminants into the borehole. Unless otherwise approved by
				the Department based on site-specific characteristics, only potable water may
				be used in drilling. In some cases, analysis of water used in drilling may be
				required;
(6) All equipment to be
				placed into the boring must be properly decontaminated before use at the site
				and between boreholes;
(7) Borings
				for wells and piezometers must not be placed through or into waste unless prior
				Department approval has been granted and sufficient safety precautions are
				employed;
(8) Well screens are
				required for all wells and for open standpipe piezometers. All screens must be
				factory slotted and sized to retain at least 90% of the grain size of the
				filter pack. Water table variations, site stratigraphy, expected contaminant
				behavior, and ground water flow must be considered in determining screen
				position and length. Unless otherwise approved by the Department based on
				site-specific characteristics, screens for water table observation wells and
				monitoring wells must not exceed 10 feet in length. Screens for piezometers
				must not exceed 2 feet in length. Technical justification for the screen length
				chosen must be provided;
(9) Well
				screens must be located to readily detect changes in ground water chemistry in
				each potentially affected hydrogeologic unit. Monitoring wells must not be
				screened across hydrogeologic unit boundaries. Where surficial hydrogeologic
				units exceed 20 feet in saturated thickness, a monitoring well cluster of two
				or more wells is required, the screens of which must each not exceed 10 feet in
				length;
(10) Proposals for
				alternate instrumentation for piezometric measurements in sediments with
				hydraulic conductivity of less than 10E-6 cm/sec may be submitted to the
				Department for review and approval;
(11) The sand pack surrounding the well
				screen must consist of clean, inert siliceous material. The sand pack must
				minimize the amount of fine material entering the well and must not inhibit the
				flow of water into the well. The sand pack must be placed in the annular space
				around the well screen and extend two feet or twenty percent of the screen
				length (whichever is greater) above the top, and six inches below the bottom,
				of the screen. The sand pack material must be placed using the tremie method
				and must avoid bridging. The sand pack must be checked for proper placement. A
				finer grained sand pack material (100% passing the No. 30 sieve and less than
				2% passing the No. 200 sieve) six inches thick must be placed above the sand
				pack and below the bentonite seal;
(12) Bentonite must be placed above the sand
				pack using the tremie or other approved method to form a seal at least three
				feet thick. If pellets or chips are used, sufficient time (usually 4 to 24
				hours) must be allotted to allow for sufficient hydration of the bentonite
				prior to placement of overlying materials;
(13) Grout of cement and bentonite, bentonite
				alone, or other suitable, low permeability material, if approved by the
				Department, must completely fill the remaining annular space to the base of the
				surface seal. The sealing material must set up without being diluted by
				formation water, and must displace water in the annular space to insure a
				continuous seal. The sealant must be placed under pressure using a tremie or
				other method approved by the Department. Backfill of native material to
				construct the annular seal is prohibited; and
(14) A bentonite or concrete surface seal and
				protective, lockable steel casing must be installed around all monitoring wells
				and long-term observation wells and piezometers. If a concrete surface seal is
				constructed, it must extend from below the level of frost action at least to
				the ground surface. The surface seal must prevent surface water or runoff from
				ponding around the well casing. The protective steel casing must be set at
				least six inches lower than the base of the surface seal and extend
				approximately two inches above the top of the PVC riser. The surface seal must
				be designed to minimize or eliminate heaving due to frost action. Both the
				surface seal and the protective steel casing must be designed and constructed
				so that neither is mechanically coupled to the PVC riser. The diameter of the
				protective casing must be at least two inches larger than the PVC riser. The
				protective casing, as well as the PVC riser, must be vented near the top to
				allow the escape of gasses and the equilibration of water level with
				atmospheric pressure changes. The protective casing must also have a drain hole
				at the base. A permanent, distinctive and readily visible marker identifying
				the well's designation must be affixed to the protective casing or near the
				well; and a means to locate the well during periods of high snow cover must
				also be provided. In areas of traffic, bumper guards or other suitable
				protection for the well are required.