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[ ISBN 0-97411009-4 ]

$24.95 (US)

(240 Pages; Text + Illustrations)

Pursuant to Section 2725(a) of the California Code of Regulations, a Soil and Water Investigation Phase of an environmental cleanup (former gasoline service station site) includes the collection and analysis of data necessary to assess the nature and vertical and lateral extent of an unauthorized release, and the determination of a cost effective method of cleanup. Using the information obtained during the investigation, the responsible party must propose a Corrective Action Plan to assess environmental impacts including but not limited to the hydrogeologic characteristics of the site and surrounding areas where the unauthorized release has migrated or may migrate [Cal. Code Reg. Section 2725(e)(2)]. The responsible party must conduct a feasibility study to evaluate alternatives for remedying or mitigating the actual or potential adverse effects of the unauthorized release [Cal. Code Reg. Section 2725(f)]. Once the Corrective Action Plan is submitted and approved by the regulatory agency it must be implemented by carrying out the cost effective alternative selected during the Soil and Groundwater Investigation Phase for remediation or mitigation of the actual or potential adverse effects of the unauthorized release [Cal. Code Reg. Section 2726(a)].

This is a report of a feasibility study to assess groundwater velocity and pumping and treatment of groundwater to remove dissolved contaminants. This study involves the use of a state of the art computer program for analysis of step drawdown and constant rate aquifer pump testing data. Nonlinear least squares parameter estimation using a Gauss-Newton Linearization Method is utilized in obtaining the final refined set of parameter estimates which provide a best fit of the conceptual model to the data. The estimated parameters include Transmissivity ('T'), Hydraulic Conductivity ('K'), Storativity ('S'), Specific Yield ('Sy') and Hydraulic Conductivity Anisotropy Ratio ('Kz/Kr').

The estimation of the above listed hydrologic parameters enables the caluculation of approximate groundwater velocity in the immediate area. The rate of migration of a groundwater contaminant plume which is primarily comprised of soluble chemicals such as Methyl Tert Butyl Ether can be approximated according to the groundwater velocity in the immediate area. The rate of contaminant plume migration is an important parameter in the evaluation of impacts of an unauthorized release on nearby public waters and waterways.



I. Aquifer Pump Testing Protocol

      A. Introduction
            1. Objectives
      B. Aquifer Pump Testing Equipment
            1. Manual Measurement of Depth to Well Water
            2. Automated Measurement of Water Column Depth
            3. Pump and Effluent Discharge System
      C. Step Drawdown and Constant Rate Extraction Test
            1. Step Drawdown Test
            2. Constant Rate Extraction Test
      D. Computer Modeling of Aquifer Pump Test Data
            1. Supporting Materials
            2. Software

II. Analytical Results

      A. Hydrology
      B. Conceptual Model
      C. Visual Curve Matching (Manual Calibration)
            1. Step Drawdown
            2. Constant Rate
      D. Automatic Curve Matching
            1. Automatic Calibration; Partially Penetrating Well
            2. Automatic Calibration; Fully Penetrating

III. Discussion

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