KIRTLAND AIR FORCE BASE ALBUQUERQUE, NEW MEXICO ...

APPENDIX B
If the boring is overdrilled beyond the bottom of the proposed sump elevation by more than
10 ft, backfill the borehole with filter pack material to an elevation approximately 5 ft below
the proposed bottom of sump elevation
Use a 5-ft PVC sump, 25-40 ft of 0.01-inch PVC slotted screen, and blank casing to the top
of the well stick-up. The top of the screened interval will be at least 5 ft above the existing
water table. The sump will extend 5 ft below the bottom of the screened interval.
Centralizers will be installed at 40-ft intervals and at the top and bottom of the screened
interval in all wells deeper than 50 ft.
Once the casing has been slowly removed from the borehole, backfill the borehole and
annular space from a maximum of 1 ft below the bottom of the sump to a minimum of 2 ft
above the well screen with a filter pack (10/20 silica sand). The filter pack will be placed
using a tremie pipe to avoid bridging and ensure a continuous filter pack throughout the
screened interval of the well. Next, a bentonite chip seal will be installed for a thickness of
10–20 ft and hydrated with potable water every 1 ft to ensure a competent seal. The thickness
of the seal will be dependent on the lithology of the aquifer formation such that the bentonite
seal extends form the top of the filter pack to within 5 ft of the most consolidated uit above
the water table. The bentonite seal will be a minimum thickness of 5 ft. Installation of a
thicker bentonite seal is currently used for monitoring wells at the Kirtland AFB to ensure
that there will be no intrusion of grout from above the seal into the filter pack material below
the seal.
Install a 20 percent high solids bentonite grout mixture over the bentonite seal using a tremie
pipe. The mixture will consist of 20 percent by weight of sodium bentonite powder. Install
the bentonite grout to within 30 to 50 ft of the surface. The high-solids bentonite grout is
currently and successfully used for well installation at the base to inhibit intrusion of grout
into the well‘s filter pack and screen.
To the surface, install a cement/bentonite grout mixture over the high-solids bentonite grout
using a tremie pipe. The mixture will consist of 94 pounds of Portland cement to 7 gallons
of approved water and 3 percent by weight of sodium bentonite powder.
Install an 8-inch by 5-ft protective round steel casing and a 4-ft by 4-ft by 4-inch concrete
pad mounded in such a way as to direct surface runoff from the casing. Install 4-inch by 5-ft
steel bollards around each well on the outside of the concrete pad. Drill a drain hole in the
protective casing above the concrete surface. In locations subject to freezing, the finished
pad must be designed to resist damage caused by frost heaving.
An approximate stick-up height of 3 ft is required for each well to accommodate the
dedicated pump system.
The well will be equipped with a security lock. All locks will be keyed alike. The well will
be tagged with a corrosion-resistant identification stamped on the protective casing which
identifies the well number, depth, date of installation, and the adjusted top of casing
elevation. The well will also be clearly designated as a monitoring well. The casing will be
coated with protective paint as required by the base.
Some wells may have to be finished flush with the ground or pavement if they are in areas of
heavy traffic. This requirement shall be stipulated in the project specific addenda. Flush
Kirtland AFB
SOPs for Field Investigations B-36 April 2004