Grando, a field engineer for engineering firm Treviicos Inc., captured the installation of tremie pipes before concrete placement for the drilled shaft on the North Washington Street Bridge replacement project in Boston. Grando shot from a temporary bridge that provided access to the different cofferdams where the drilled shafts were located. Installing the shafts involved stable, uncased excavation through the glacial till and weathered rock that is 6 in. smaller in diameter than the cased portion of the drilled shaft above the soil strata. During excavation, the slurry level in the drilled shaft is maintained at least 5 ft above the water level surrounding the casing or within 2 ft to 3 ft below the top of the casing, Treviicos says. 

When completed in 2023, the $177-million project to replace the approximately 120-year-old structurally deficient bridge will include widened sidewalks and separated bicycle lanes and bus rapid transit lanes. The span carries traffic over the Boston Inner Harbor between the North End and Charlestown.