3-02. SUBSURFACE EXPLORATIONS 



A preliminary subsurface exploration program was recently 

 completed at the site during the period 28 to 31 March 1988 to 

 obtain subsurface information for geotechnical design purposes, 

 and to provide information on soil and groundwater quality. 

 The program consisted of three test borings drilled from land 

 using a truck-mounted rotary drill rig. A fourth boring was 

 made from within the wooden frame warehouse pier structure with 

 a portable skid rig over the Charles River. The borings were 

 monitored in the field by H&A personnel. As-drilled locations 

 of the borings were determined by H&A by measuring from 

 existing site features shown on Figure 2. Ground surface 

 elevations were determined by H&A using optical survey methods. 



All four borings were advanced using 3-in. diameter casing to 

 the specified depths. Potable water was introduced into the 

 boring to facilitate drilling. Split-spoon samples were taken 

 from all borings at depth intervals, typically not exceeding 

 five feet, and at changes in soil type. For the purpose of 

 this report, continuous samples were generally taken at two 

 foot intervals through the surficial fill deposits. All 

 borings were terminated in the glacial till stratum. Boring 

 logs prepared by the boring contractor are included in 

 Appendix A. 



3-03. GROUNDWATER OBSERVATION WELLS 



Groundwater observation wells were installed in completed 

 boreholes B102, B103, and B104 . The well tips were installed 

 at depths of approximately 15 ft to 2 ft. below ground 

 surface. The observation wells consist of 2.0 in. I.D. machine 

 slotted PVC well screen, installed from the well point to the 

 ground surface, to allow the observation of tidal influences on 

 the site. The top of each observation well was sealed with 

 cement and bentonite, and encased in a protective roadway box. 

 Groundwater Observation Well Reports are included in Appendix B 

 of this report. Groundwater levels measured during periodic 

 monitoring of the observation wells for the period 29 March to 

 5 May 1988 are also included in Appendix B. The corresponding 

 tide level recorded at the time of the groundwater measurements 

 is also noted on the monitoring reports. From the groundwater 

 data obtained at the site, it is noted that groundwater levels 

 observed at observation wells B102 (OW) and B103 (OW) vary 

 appreciably with tidal fluctuations, while the water levels 

 observed at B104 (OW) do not. 



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