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and March), and Newhall Station recorded 30.46 inches of rainfall during the four month
period. Nearly half of this amount occurred during two storms in early February.

As might be expected, given the precipitation data above, water levels recorded during 1991
were lower than those observed during 1992 monitoring. This difference was most
pronounced in wells located along the main portion of East Firebreak Road ridgeline
(e.g., 40 to 50 feet in wells MW-ll, C-7A and MW-IO) and less so (approximately 10 to 15

feet) in wells lower along the ridgeline, such as MW-9 and MW-13.

Well Hydrograph Data - Early 1991 to August 1991: In general, most water levels in wells
remained relatively stable during early 1991 to August, 1991, or declined slowly. Stable
water levels typically were observed in ridgeline wells, such as those just mentioned and
others located along lower ridges, such as MW-19 and MW-2l to the north and MW-8 and

MW-9 to the south (Plate 7A). Declining water levels were observed in wells located in
lower drainage areas of Elsmere Canyon, such as well pairs C-13/C-14, MW-l/MW-Z, and
pairs MW-17/MW-22. An exception to declining or stable trends was observed in wells
located along the lower northwest flank of East Firebreak Road ridgeline, such as MW-3,

MW-4 and MW-6B. These wells which are completed in San Gabriel Formation appeared
to show steady to slightly rising water levels, although these did not reach the initial April
water level readings in 1992 data.

Well Hydrograph Data - April 1992 to September 1992: Water levels beginning April 10,
1992 were higher in all project property wells than last measurements of the 1991
investigation (August 1991), indicative of the heavy winter rainfall. Although bi-weekly

water level measurements for 1992 monitoring did not begin until after most precipitation
ended, the effects can still be seen in the well hydrograph data from April to
September, 1992 (Appendix E). These data provide opportunity to evaluate qualitative rates
of infiltration and overall response of the local groundwater system to heavy precipitation,
as well as seasonal trends.

The 1992 data can be grouped into three main trends that include: 1) falling water levels;
2) rising water levels; and 3) stable water levels. However, in numerous instances, one or
two of these trends have been superimposed upon the overall trend, resulting in several
subsets or special cases. These effects may be due to variable rates of infiltration of
precipitation and/or variable rates ofgroundwater movement due to aquifer heterogeneities,

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