groundwater level monitoring data are included herein as 

 Appendix C. 



It is important to note that water level readings recorded in 

 the observation wells were made at times and under conditions 

 stated on the groundwater monitoring reports. It is emphasized 

 that the actual groundwater levels may differ from the observed 

 levels and that fluctuations in the level of the groundwater 

 may occur due to variations in tide level, season, rainfall, 

 temperature, and other factors. Also, groundwater levels at 

 the time of construction could differ significantly from water 

 levels observed during this study particularly if leaking 

 sewers are found near the site. 



Water levels throughout this particular site were observed to 

 respond to tidal fluctuations. The tidal response at a 

 specific location depends on the permeability of the soils 

 between the well location and the source of free water. As may 

 be seen in the groundwater observation well data contained in 

 Appendix C, the response to tidal action varies considerably 

 across the site due to the complex nature of the near surface 

 fill soils. Groundwater level data indicate that water levels 

 at observation wells B102 and B103 vary appreciably with tidal 

 fluctuations while water levels at B104 do not. In general 

 however, groundwater levels at the site should be expected to 

 reflect tide levels in Boston Harbor typically ranging from 

 El. 96.5 (Mean Low Water - MLW) to El. 105.9 (Mean High Water - 

 MHW) . 



3-04. TIDE LEVELS 



The U.S. Army Corps of Engineers has developed data on observed 

 tide levels in Boston Harbor and the predicted tide level 

 frequency of occurrence. The following tide level frequency 

 data are estimated by the Corps for data through August 1979: 



Frequency High Tide Elevation 



In Years (NACA Project Datum) 



1 108.97 



5 109.77 



10 110.17 



20 110.57 



25 110.97 



50 111.07 



100 111.37 



200 111.77 



Note ; El. 0.0 NACA Project Datum is 100.00 ft. below 



National Geodetic Vertical Datum (USC and GS Mean Sea 

 Level Datum of 1929) . 



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