Current through 2024-38, September 18, 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.
B.
Geologic sampling. A boring
program is necessary to define site hydrogeology. Borings must be carefully
sampled to provide surficial and lithological information.
(1) Borings must be continuously sampled
throughout the length of the hole at all locations where surficial stratigraphy
and bedrock characteristics have not previously been determined.
(2) In any additional borings not
continuously sampled, samples must be taken at five foot intervals, at each
stratigraphic change, and at the screened interval in surficial deposits and,
in rock, as required by the Department.
(3) At a minimum, the screened interval of
each surficial installation must be analyzed.
(4) At well or piezometer clusters,
continuous samples must be taken from the surface to the base of the deepest
boring. Other wells or piezometer borings in the cluster must be sampled at the
screened interval.
(5) Bedrock
must be sampled with a standard size NX or larger diameter core barrel. All
other materials must be sampled using the split spoon or equivalent
method.
(6) Bedrock refusal must be
distinguished from boulder refusal by a minimum of ten feet of continuous rock
core. Where core lithology does not conform to known bedrock characteristics, a
longer core may be required to confirm bedrock refusal.
(7) Core samples must be securely stored and
accessible throughout the life of the facility.
(8) Unconsolidated samples must be retained
for five years after the original permit is issued. The location of the storage
area must be designated in the operating record for the solid waste
facility.
C.
Well
and piezometer development. Monitoring wells and piezometers must be
constructed, installed and developed in a manner which assures that the well or
piezometer is in good hydraulic contact with the hydrogeologic unit and that
samples obtained will be representative of formation water. Wells installed for
the purpose of ground water sampling and analysis must be capable of producing
samples low in turbidity.
(1) All wells and
piezometers must be developed as soon as possible after installation but not
before the well seal and grout have set.
(2) Water must not be introduced into the
well except with approval from the Department.
(3) Any contaminated water withdrawn during
development must be properly managed.
(4) The entire saturated screened interval
must be developed.
(5) Well
development methods selected must insure that sediment-free water can be
obtained. The Department may require multiple attempts at well development to
ensure that sediment-free water can be obtained.
(6) Acceptable well development methods are
specified in US EPA (1992) "RCRA
Ground-Water Monitoring: Draft Technical Guidance", and references listed
therein. The development method selected must be appropriate for the
stratigraphy/conditions encountered. Placement of screens in fine grained
strata may require gentle development techniques to avoid pulling sediments
into the well. The selected method must minimize to the greatest extent
possible the amount of turbidity in the well.
D.
In-situ hydraulic conductivity
testing and well performance evaluation. In-situ hydraulic conductivity
testing of each monitoring well must be performed to provide information on the
hydraulic conductivity in the immediate vicinity of the monitoring well. A well
performance evaluation must be performed on each monitoring well to determine
the rate at which each well can be pumped without significant continued
drawdown. In-situ hydraulic conductivity testing must be done in all monitoring
wells and piezometers. The testing methods must not introduce contaminants into
the well. Any contaminated water removed from the well must be properly
managed.
E.
Report on the
Design, Construction and Development of Monitoring Wells and
Piezometers. The following information on the design, construction and
development of monitoring wells and piezometers must be submitted to the
Department after development of monitoring wells is completed.
(1) Standard drillers logs showing driller's
name, start and finish data, boring designation, casing, sampler, core barrel
and hammer specifications, sample blow counts, vane readings, moisture content,
location of the water table during drilling, water lost during drilling, degree
of sample recovery and other appropriate information must be submitted for each
boring.
(2) A well installation
detail diagram with a minimum vertical scale of 1 inch equals 5 feet showing
the complete borehole and the complete well or piezometer installation in cross
section, including well or piezometer designation; the elevations of riser and
screen and of all annular materials; the surface elevation and the of top of
riser and top of protective casing. Sampling intervals, sample designations,
and if practical, analytical results must also be included. Borehole
stratigraphy, as interpreted by the geologist in charge of the installation is
also required as part of the installation diagram. Logs of surficial deposits
should include a description of matrix and clasts, mineralogy, roundness,
color, odor, appearance, and behavior of materials. Rock core logs must
describe the lithology, mineralogy, degree of cementation, color, grain size,
and any other physical characteristics of the rock noted, percent recovery and
the rock quality designation (RQD). The logging system used to provide the
information must be a geological logging system. Engineering logging systems
are not acceptable.
(3) Information
on the method of well development used for each monitoring well and the results
of the development.
F.
Routine Inspection, Maintenance and Testing of Monitoring Wells.
All monitoring wells must be maintained in a manner that ensures their
continued performance according to design specifications over the life of the
monitoring program. All results, as well as a description of any maintenance
conducted, must be included in the reports submitted to the Department.
(1) Inspections of surface seals for heaving,
settling and cracks must occur each time sampling and/or water elevation
measurements are carried out, and the results recorded on the field
sheets.
(2) At least annually, the
depth of each well must be determined, and the results reported in the annual
report.
(3) At each monitoring well
where low-flow sampling is not used, a performance evaluation of the monitoring
well must be conducted at least annually, to determine the pumping rate at
which the well will be purged and sampled. This data must be included in the
annual report for the facility.
G.
Replacement of wells and
piezometers. All wells and piezometers must be properly protected and
maintained to insure their integrity. If water quality or any other data show
that the integrity of a monitoring well is lost, the well must be replaced and
sampled within a time period not exceeding 120 days after written notification
by the Department. When a well is damaged or for any other reason cannot be
sampled, the Department must be notified in writing no later than fifteen days
from the discovery of the damage.
(1) A
location for the replacement well or piezometer must be approved by the
Department prior to its installation.
(2) The initial sample for a replacement well
at MSW landfills must consist of the Appendix A of this chapter,Column 3
parameters.
H.
Abandonment of wells, piezometers and borings. Wells, piezometers and
borings abandoned for any reason must be fully and completely sealed in a
manner appropriate to the geologic conditions to prevent migration of water or
contaminants along the borehole. Generally such sealing must include:
(1) Removal of all material installed in the
original borehole including casing, screen and annular materials to the
greatest extent possible. Any casing which cannot be withdrawn intact must be
ripped and perforated and then augered or washed from the hole.
(2) Sealing by pressure injection from bottom
to top with cement bentonite or other appropriate material to within five feet
of the ground surface. The upper five feet may be backfilled with native
material, and the entire site must be restored to a safe condition. Where the
surrounding geologic deposits are highly permeable, alternative methods of
sealing may be required by the Department to prevent migration of grout into
the surrounding formation.
(3)
Documentation of the abandonment through a written description of the
procedures employed, drilling methods and depths, borehole depth and volume and
type of sealant employed is required.
