Page 843 - anf1995elsmere_deis

Piezometric fluctuations in selected non-pumping wells screened within the
Saugus Formation in the Eastern Basin region from approximately 1961 to 1987, averaged
20 feet to 40 feet, apparently in response to seasonal effects. A maximum fluctuation of
about 160 feet was observed in one well (Slade, 1988).

Piezometric data from Saugus wells in the Eastern Hydrographic Subarea south of the
Holser fault indicated elevations of 50 feet to 100 feet above those for 1967, which was a
generally low water level period (Slade, 1988). The degree to which this fault system
influences groundwater flow in the Saugus Formation reportedly is not certain (Slade, 1988),
but it appears at least to be a partial barrier to groundwater flow in the deeper portions of

the Saugus. Finally, on a local scale, water levels measured between 1985 and 1987 in wells
located within the Newhall region (specifically, the Newhall Refinery) indicated fluctuations
of 5 feet to 7 feet (The Mark Group, 1987).

Sylmar Basin Subarea: Groundwater contours for 1988 indicated water levels to be on the

order of 50 to 100 feet bgs in most of the Syhnar area (Blevins, 1989). Historically,
near-surface groundwater conditions were reportedly present within several areas of the
basin in the early 1900s, but levels have subsequently declined due to pumping (Brown,
1975). Based on water level data for the eastern portion of the Sylmar Basin available in
1971, water levels declined approximately 80 feet from historic high-water levels observed
in 1944-1945 (Brown, 1975). This has been as a direct result of pumpage and export of

water from the Mission well field to the San Fernando area, exceeding natural and imported
water recharge to the Sylmar area.

8.3.4 Ragional Aguifer Parametars

Eastern Hydrographic Subarea: Because there are essentially no available aquifer test data
for alluvial aquifers in the Eastern Hydrographic Subarea, theoretical estimates of aquifer
parameters of transmissivity (T) and hydraulic conductivity (K) have been derived for these
deposits (Slade, 1986). In these calculations, values of well yield (Q, in gallons per minute
_ (gpm)) and well drawdown (s) were estimated from drillers’ logs or from efficiency tests
performed on local wells by the Edison Company. Areas of high T values (>

500,000 gallons per day per foot (gpd/ft) and low T values (< 12,000 gpd/ft) were identified
in the area using this approach (Slade, 1986).

115

21351000120
009/700