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M d Mr. Mike Infuma 2 December 16, 1991 The folllowing sections describe the field procedures for the additional assessment efforts. INVESTIGATION METHODOLOGY Purpose The purpose of this additional investigation is to further identify the lateral extent of the dissolved hydrocarbons in groundwater,by employing the Hydropunch®technique at an ; estimated five locations. f� Scone of work 'The scope of work for this investigation includes the following work elements: • Preparation of this workplan addendum. • Obtain permits for encroachment into city property and hydropunch activities. o Chemical anaiys�s.ef water samples for selected petroleum hydrocarbons, • Report preparation. - Hydronunchin� Prior to the commencement of field work, all underground utilities wilI be located. This will _ be done through use of Underground Services Alert(USA) and a subcontracted utility location service. A California C-57 licensed dr:,'ler will be subcontracted to perform the hydropunching. The rT field geologist will conduct a tailgate safety meeting at the beginning Of the day to insure that field activities are perfort .d in accordance with the site specific Health and Safety Plan. Hydropunching is a method of"drilling" in which instruments are pushed into the ground i rather than rotated into a hole as it is being cut. The prime advantage of this technique is that no waste material is produced. During hydropunch activities, a pike assembly is desired depth. An outer Pipe(protective sleeve) hydraulically pushed into the ground to the is then pulled back,revealing a finely perforated pipe which groundwater may flow into. A s tiny bailer may then be lowered into the inner pipe and a groundwater sample collected. The entire pipe assembly is then jacked out of the ground. Hydropunch holes will be tremmied from bottom to ground surface with cement-bentonite cement after each hoIe is made. Sampling Locations -- — -- t- — ----- — - The first hydropunchO boring/sampling location will be-located-sufficiently downgradien beyond the anticipatcd limits of hydrocarbon migration. Subsequent Hydropunch® drilling/samplinglocations will be determined by analvr-:- ;results from the first point,as provided by an an site laboratory. A total of five Hydropuach® locations are planned (Figure 3)