stable and shall be verified straight before beginning installation.
3.4.1
Casings and Screens
Well casings, screens, plugs, and caps shall be decontaminated prior to
delivery by the manufacturer and shall be certified clean. Materials shall
be delivered, stored, and handled in such manner as to ensure that grease,
oil, or other contaminants do not contact any portion of the well screen
and casing assembly prior to installation. If directed by the Contracting
Officer, the well screen and casing assembly shall be cleaned with high
pressure water prior to installation. Personnel shall wear clean cotton or
surgical gloves while handling the assembly. Centralizers shall be used to
ensure that the well screen and casing assembly is installed concentrically
in the borehole. When the assembly has been installed at the appropriate
elevation, it shall be adequately secured to preclude movement during
placement of the filter packs and annular seals. The top of the well
casing shall be capped during filter pack placement.
3.4.2
Primary and Secondary Filter Packs
Primary and secondary filter packs shall be placed as indicated on the
approved well construction drawings to fill the entire annular space
between the screen and casing assembly and the outside wall of the
borehole. Place both the primary and secondary filters with a tremie pipe
in accordance with EPA 600-4-89-034 and ASTM D 5092. Placement of the
primary and secondary filters by gravity or free fall methods is not
allowed. Control speed of filter placement to prevent bridging and to
allow for settlement. Prior to commencement of work, equipment and methods
required to place filters shall be approved by the Contracting Officer.
3.4.3
Bentonite Seal
Bentonite shall be placed as a slurry through a tremie pipe. Control speed
of bentonite placement to prevent bridging or segregation of slurry.
Additional water shall be added to the annular space as directed by the CPC
to ensure complete hydration of the bentonite. Bentonite shall cure a
minimum of 48 hours before the placement of cement grout to ensure complete
hydration and expansion of the bentonite.
3.4.4
Neat Cement Grout
Cement grout shall be placed in the annular space above the bentonite seal
as indicated on the well construction drawings. Cement grout shall be
placed as a slurry through a tremie pipe, and injected under pressure to
reduce chance of voids. Grout shall be injected in one continuous
operation until full strength grout flows out at the ground surface without
evidence of drilling cuttings or fluid. Cement grout shall cure a minimum
of 48 hours before beginning well development operations.
3.4.5
Well Head Completions
Well head completions shall be as indicated and as specified herein.
3.5
WELL DEVELOPMENT
Well development shall be in accordance with EPA 600-4-89-034 and ASTM D
5092 except as modified herein. Bailing, surging, and
pumping/overpumping/backwashing are acceptable development methods. Air
surging and jetting are prohibited. Method of development shall be chosen
SECTION 02525N
Page 15
Previous Page
