Buried Building Remnants Challenge McCarty Companies
A privately owned, five-story student dormitory in Lowell, Massachusetts, was built in just 14 months by developer Vision Properties and a team of engineers, architects and contractors working under an accelerated construction schedule.
Located on a 2-acre tract overlooking the Merrimack River, the $40 million student housing project was built on the site of the former headquarters of Lowell Five-Cent Savings Bank, which was demolished to make way for the dormitory.
While the new student housing is situated not far from UMass Lowell, it is not affiliated with the institution and is owned and managed privately. The developer reportedly saw a need for additional student housing due to anticipated university expansion, and decided it was worth the risk to construct it without academic affiliation.
McCarty Companies of Leominster, Massachusetts, performed the earthmoving and utility construction for the building project under the overall management of Patrick McCarty, Owner and President, with direct jobsite supervision by Foreman Robert D'Onfro. McCarty was also responsible for overseeing asbestos abatement and demolition of the existing bank building by subcontractors.
Buried Building Remnants
Site work was particularly challenging on this project due to the nature of the soil and the tight construction schedule of the developer, who planned to have the new building occupant-ready for the 2017-2018 school year.
McCarty started site excavation in July 2016 after clearing trees and installing erosion controls such as silt fence and hay bales. As earthmoving began in earnest, equipment operators worked six 10-hour days a week to stay on the compressed timetable.
In addition to general and building excavation, McCarty was responsible for processing existing site fill containing buried remnants of buildings razed years ago. Such building components and materials as brickwork, concrete foundations and granite blocks had simply been left in place and backfilled when the structures were demolished. Soils engineers determined that this fill was not suitable to support a new multi-story building, so McCarty had to excavate the material down to virgin ground. This was done under the direction of the engineers. In some places, the unsuitable material was 27 feet deep. Large chunks of concrete and granite block in the fill were initially broken into smaller pieces that could be processed in an on-site Metso mobile crusher and screening plant where minus 3-inch size aggregate was produced suitable for reuse on site.
An estimated 70,000 tons of raw fill was processed through the Metso plant.
Sizing Equipment to Fit the Job
McCarty employed a fleet of late-model various sized Caterpillar earthmoving machines to rapidly handle the difficult soil and meet the project's tight construction schedule. This included a Cat 330DL Excavator used for general site digging, and a Cat 325 Excavator equipped with a Gorilla hydraulic demolition hammer to break down larger sections of concrete foundations or granite block. A Cat 725C Off-Highway Truck transported raw fill to the Metso processing plant, where a Cat 319DLN Excavator and Cat 938G Wheel Loader took processed material either directly to a fill area of the site or to a stockpile for future use as needed.
Processed material was analyzed by soils engineers to ensure its structural suitability before being placed and compacted in 1-foot lifts in such areas as the building pad, roadway and parking lots. Two Cat dozers, a D5H and D4GXL, were employed to push up stockpiles of processed fill or to grade material as it was placed in fill areas. A Cat CS423E Vibratory Roller provided the compaction.
McCarty used two Caterpillar rubber-tracked mini-excavators, a 303 ECR and a 305 DCR, to excavate, backfill and compact in exceptionally tight areas. Other smaller pieces of equipment were utilized where necessary, including a Cat 242B Skid-Steer Loader.
Utilities Run Through Building Site
As part of its contract, McCarty excavated all buried utilities and structures. Earlier soil test pits had indicated that multiple foundation walls, pipes, and other unsuitable materials were to be found throughout the site. Furthermore, demolition drawings indicated there were several underground utilities running through the building area, among them, natural gas, electrical, water, drainage and sanitary sewer lines. McCarty crews excavated and removed all of the existing utilities, and excavated, installed and backfilled new water, sewer and drainage lines in newly designated locations. In addition, the contractor excavated and backfilled gas and electric lines that were installed by utility companies.
Working Quadrants Help Speed Project
The building site was divided into successive quadrants to speed construction. As McCarty completed site work in a quadrant, concrete workers were right on the heels of the earthmoving contractor, forming and placing the dormitory's concrete footings and foundation walls.
McCarty finished its site work in August 2017, with one of its last tasks being the rough-grading of gravel base beneath parking lots and access roadway to within 1-inch of finish grade, while the paving contractor handled fine-grading before placing two courses of bituminous concrete pavement.
The new dormitory was completed for occupancy in August, just 13 months from the time that McCarty Companies began site excavation, and a few weeks before the September start of classes.