Specification 02560 - Landfill Gas Extraction Wells Page 3 of 4
January 2021
3066.21
B.
Wells shall be drilled to the minimum diameter and the specific depths shown on
the Drawings. CONTRACTOR shall drill the wells using bucket-type augers and
dry drilling equipment; wet rotary drilling equipment may not be used.
Well depths shown on the Drawings are estimated based on projected top of
waste elevations and may be adjusted in the field by ENGINEER. At no time shall
the drilling extend deeper than the bottom of well screen elevation.
If water is encountered in a borehole, then CONTRACTOR may be directed to
drill beyond the point that it was encountered. If wet conditions remain, then
drilling may be terminated and the length of perforated pipe adjusted by
ENGINEER, or the well may be relocated. If wet conditions cease (e.g., due to
trapped water layer), then drilling will continue to the design depth.
As soon as drilling is completed, a safety screen shall be placed over the top of
the borehole. This screen shall stay in place until backfilling is within 4 feet of
the surface. Safety screen size should be large enough to accommodate all
backfill materials and any tools used during backfill yet not large enough for any
human to accidentally fall through.
Wells shall be drilled straight and plumb and the well pipe shall be installed in
the center of the borehole. CONTRACTOR will take all compression off of the
pipe by mechanical means and center the pipe in the middle of the borehole
before starting to backfill.
PVC well pipe shall be solvent cemented and mechanically fastened with
stainless steel fasteners.
CONTRACTOR shall not leave boreholes open over night, if a bore hole is started
a well shall be constructed within the borehole prior to CONTRACTOR leaving
the site.
CONTRACTOR shall provide odor control during construction activities. Odor
control measures shall be approved by OWNER prior to use.
3.2 BACKFILLING
A.
Backfilling the borehole shall commence immediately after drilling is completed
and the PVC pipe has been installed. Backfill materials shall be installed as
indicated on the Drawings and as approved by ENGINEER.
Stone Aggregate shall be poured or scooped through the safety screen at a rate
that will not endanger the integrity of the well casing and limits the potential for
bridging.
The Sand/Gravel Filter shall be poured through the safety screen until a layer at
least 1-foot thick above the Stone Aggregate is formed.
SANBORN HEAD
