boreholes MW2 and MW5. The annular space between piezoineters was sealed with a

mixture of bentonite and cement grout, and the piezometers were developed using

compressed air. The resulting piezometer and well nests were used for

measurements of the vertical distribution of hydraulic head in the dolomite,

for two pumping tests, and for obtaining high--quality groundwater samples that

were analyzed for major cations and anions as well as environmental isotopes

(3H, 180).



Location of Horizontal Fractured Zones



    At the detailed monitoring site, less than 2 ft (0.3 m) of silty soil

covers the dolomite. Direct evidence of fracture discontinuities observed

during installation of well. Mi included loss of drilling fluids at elevations

of 577 and 600 ft (176 and 183 m) above sea level and voids at 577 and 582 ft

(176 and 177 m). While drilling at an elevation of 563 ft (172 m) at MW2,

water erupted 40 ft (12 m) above the ground at MWI. This shows a direct

connection between wells NMl and MW2, which are 170 ft (52 m) apart.



    Geophysical logs, including three-arm caliper, spontaneous potential,

single-point resistivity, natural gamma radiation, and borehole temperature

were obtained at several monitoring wells prior to casing installation.     Figure

6 shows a suite of logs for well MWl, which is cased from the surface to 40 ft
(12 in) and has a total depth of 242 ft (74 mn). Numbers on the left-hand axis

of Figure 6 are corrected elevations relative to mean sea level. Offsets

appear in the temperature log at elevations of 555 ft (169 m) and 652 ft (199

in). This log was run in the spring of 1988, when cold recharge water was

entering the aquifer.   Temperature increases at the offsets suggest that either