SITE INFORMATION AND CORRESPONDENCE

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Mr. James Barton April 14, 2004 Page 2 PROPOSED SCOPE OF WORK SECOR proposes injecting pre -mixed 30% potassium persulfate catalyst solution, then 10% hydrogen peroxide solution at flow rates varying from 0.5 — 5 gallons per minute (GPM) over a period of two days for a total of 840 gallons (380 pounds of hydrogen peroxide). The volume of hydrogen peroxide injected was calculated to be 2 to 5 times the stoichiometric amount required to treat the existing mass of contaminant still present on the site (greater than 1,000 micrograms per liter (ug/L)). SITE HEALTH AND SAFETY PLAN As required by the Occupational Health and Safety Administration (OSHA) Standard "Hazardous Waste Operations and Emergency Response" guidelines (29 Code of Federal Regulations Section 1910.120), and by California Occupational Health and Safety Administration (Cal -OSHA) "Hazardous Waste Operations and Emergency Response" guidelines (California Code of Regulations Title 8, Section 5192), SECOR will prepare, or modify the existing, site-specific health and safety plan (SHSP) prior to the commencement of fieldwork. Field staff and contractors will review the SHSP before beginning field operations at the site. EQUIPMENT AND SOLUTION PREPARATION The drum transfer pump, well cap, totalizer and pressure relief valve internal parts will be made of 316 SS, PVC, PP or PE plastic materials, or similar materials compatible with applied chemicals at concentrations less than 50% and temperatures less than 200 OF. Brass, lower grade steel or other incompatible materials can corrode or weaken with chemical use causing leaks and operation failure. 10% Hydrogen Peroxide Solution Mixing A solution will be mixed using 50% hydrogen peroxide, slowly added to dilute tap water in a clean truck -mounted 200 gallon plastic tank on-site. A ratio of approximately 5-7 parts clean water to one part 50% hydrogen peroxide solution will be used, resulting in an 8% - 10% hydrogen peroxide solution (25 — 33 gallons concentrate per 200 total gallons). Secondary containment beneath drums will be used during mixing. Lines and valves will be wrapped with plastic to block spray from spills. Technicians will watch for leaks in piping and spills, and neutralize with sodium metabisulfite as needed. Wellhead Preparation Wells EX -1 and EX -2 will be fitted with a 4 -inch glued coupling and screwed plug, modified with a 30 psi adjustable safety pressure relief valve, an injection port, manual pressure release valve, temperature and pressure gauges (Figure 3). The inlet peroxide line will have a totalizer or some other method to measure volume injected over time. All transfer piping and the top of EX -1 and EX - 2 well casing (except exhaust ports) will be wrapped in plastic to contain potential spills and leaks. Exhaust ports should be vented to contain liquids and kept away from field personnel. Additional quantities of dilute sodium metabisulfite solution will be kept onsite and the area surrounding the well will be bermed to contain and neutralize potential spills. The area will be marked with barricades, caution tape and signs warning of chemical hazards and no smoking. A berm made of a non-absorbent sock will be installed around the treatment area and a 1:\Chevron\95775\REPORTS\Peroxide Injection WP RevB.doc SECOR International Incorporated