The recent borings were monitored in the field by H&A 

 personnel. As-drilled locations of the borings were determined 

 by H&A by taping from the existing site features shown on 

 Figure 2. Ground surface elevations of the borings were 

 determined by H&A using optical survey methods. All boring 

 elevations are referenced to a standard Massachusetts Geodetic 

 Survey Disk denoted "ARTERY 5," located in the northerly 

 concrete sidewalk on the, approach road to the Charlestown 

 Bridge, approximately 169 ft. southeast of the centerline of 

 Chamber Street. Boring logs prepared by the Carr-Dee Corp. are 

 included as Appendix B and are shown graphically with the 

 previously drilled borings on Figure 3, Subsurface Profile A-A, 

 and Figure 4, Subsurface Profile B-B. In addition, a summary 

 of the subsurface strata encountered and the corresponding top 

 elevation of each strata are summarized in Table I - Summary of 

 Subsurface Information. 



Boring locations and ground surface elevations are shown on 

 Figure 2. The locations and elevations of each boring should 

 be considered accurate only to the degree implied by the 

 methods used. 



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

 Split-spoon samples were recovered from all borings at depth 

 intervals typically not exceeding five feet and at changes in 

 soil type. In addition, continuous samples were taken in the 

 surficial fill deposits for Chapter 21E site assessment 

 purposes. All borings were terminated in the glacial till 

 stratum. It should be noted that in boring BlOl a boulder was 

 cored in the glacial till with a BX core barrel between a depth 

 of 42.0 and 44.5 ft. 



The Standard Penetration Resistance, "N," was determined at 

 each sample level by counting the number of blows required to 

 drive a standard split-spoon sampler (1-3/8-in. I.D., 2-in. 

 O.D.) a distance of 18 or 24 in. into the undisturbed soil 

 under the impact of a 140-lb. hammer free-falling 30 in. The 

 number of blows required to advance the sampler each six inches 

 was recorded. The "N" value is taken as the number of blows 

 required to advance the sampler the last 12 in. of an 18-in. 

 sampling range (or the middle 12 in. of a 24-in. sampling 

 range) . 



An H&A geologist was present at the site during field 

 explorations to: 



o Observe and document the subsurface conditions encountered. 



o Vary the depth of subsurface explorations as well as 

 sampling location, to meet the subsurface conditions 

 encountered. 



AQX 



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