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EXECUTIVE SUMMARY

SCWC-Saugus2, and NCWD-11) and to replace one well (VWC-157) with a newer well
located in the western portion of the valley (west of the area shown on Figure ES-2).

ES-3 Objectives

In addition to meeting the requirements of the 97-005 Policy Memo (DHS, 1997), the
Purveyors have identified the following objectives that must be met by the pumping plan
for the impacted Saugus Formation production wells:

1. Hydraulically contain perchlorate that is migrating westward in the Saugus Formation
from the Whittaker-Bermite property toward the impacted production wells.

2. Hydraulically contain perchlorate that is present at wells MP-5 and VWC-157, which are
located downgradient of the impacted wells.
3. Protect downgradient production wells that are currently not impacted.

4. Restore the annual volumes of water that were pumped from the impacted wells before
they were shut down.

5. Operate the impacted wells in a manner consistent with the Purveyors’ operational plan
5
for the groundwater resources in the Santa Clarita Valley .
6. If possible, pump one or more of the impacted Saugus Formation production wells in a
manner that also contains perchlorate migrating in the Alluvial Aquifer from the
northern portion of the Whittaker-Bermite property. Unlike the previous objectives, this
is a secondary objective for operating the impacted Saugus Formation production wells,
because other long-term remedies are being developed for the Alluvial Aquifer.
Consequently, this objective is not the basis for selecting or rejecting any given pumping
plan for the impacted Saugus Formation production wells.

The pumping plan that is developed and evaluated in this report for the impacted Saugus
Formation production wells is an interim program that will operate throughout the period
of evaluating, designing, and permitting long-term remedial actions for the Whittaker-
Bermite property and nearby groundwater. It is anticipated that the pumping plan for the
impacted Saugus Formation production wells will continue to be implemented after the
long-term remedies are in place on the Whittaker-Bermite property, in part because the
pumping plan is intended to meet the water supply needs of the Purveyors.

ES.4 Methodology

The containment evaluation for the impacted Saugus Formation production wells was
performed using the regional groundwater flow model for the Santa Clarita Valley
(Regional Model). The Regional Model’s construction and calibration are discussed in detail
in Regional Groundwater Flow Model for the Santa Clarita Valley: Model Development and
Calibration (CH2M HILL, 2004a). The Regional Model simulates the temporal and spatial
variations in groundwater flow patterns in three dimensions, including the recharge and

5 This operational plan is described in the documents titled Urban Water Management Plan 2000 (Black & Veatch, 2000) and
Santa Clarita Valley Water Report 2003 (Luhdorff & Scalmanini Consulting Engineers, 2004).

RDD/041840005 (CLR2612.DOC) ES-3