In May 2019 NSI constructed a cofferdam (18x36x18 deep) around a storm drain in Newport RI to replace a failed tidal gate. The installation was straightforward and went relatively smoothly once all obstructions were cleared, the location was constrained and required close coordination for material deliveries in and out of the site.
In June 2019 NSI constructed over a 25x50x30feet cofferdam as a test cell for chemical remediation. While a relatively small cofferdam the design required several mobilizations to remove and re-configure the structure to facilitate the remedial design. The installation is designed to remove low level PCB concentrations dissolved in groundwater passing through the cell.
In September 2019 NSI constructed a series of cofferdams (18×43’, 30×30’ and 30×35’ each 18’deep) to permit excavation of gasoline contaminated soils from a closed station. The congested neighborhood and small site constrained operations to a series of separate installations to accomplish remediation.
In the Winter 2018 NSI assisted with the rehabilitation of a leaking 150 year old rock infill storage dam in Leominster. The contract involved installing 300’ feet of 25’ vinyl sheet pile as a cutoff wall. The installation of vinyl sheets dictated some changes in handling and driving using a custom mandrel to hold the plastic sheets stiff. While this method was unusual and difficult in the rocky soils of Leominster, NSI performed the installation to the satisfaction of the design engineer. The construction was completed under approval of the Mass Division of Dam Safety.
In 2019 NSI installed a 125’ retaining wall to facilitate the construction of a 12,000sf building foundation. The contract manager reached out to NSI once he realized the sandy/clay soils and tight site conditions would require the shoring half the new foundation. Cantilevered 50’ sheet piles allowed foundation forms to be installed without bracing obstructions.
In 2019 NSI installed a cofferdam for a new sewer pump station in Fall River. The 32’x32’x26’ coffer dam used 2 levels of bracing and 35’ PZ22 sheet piles. High groundwater levels and the new configuration required 2 hydraulic beams to promote the installation and beam removal once the station was completed.
Project Details: In September 2019 NSI was awarded a contract to install 450’ feet of retaining walls to permit excavation of coal tar contamination from a 100yr old manufacturing operation. 50’ sheets were installed along half the property boundary at former loading docks. Initial attempts at installation were halted to remove over 2000 tons of deep concrete foundations and piers buried at the site. In the end over 13,000 cu yds of contaminated soil were excavated and delivered to an out of state remedial site.
After the completion each sheet pair was pulled and steam cleaned to remove any vestigial tar contamination before leaving the site.
NSI Contracting was awarded the shoring needed for a new precast culvert along Rt. 1 in East Lyme CT. The project was conducted in phases. First parallel lines of 40’ sheet piles were installed along the roadway to install a new 36” sewer line crossing. Later portions of those walls were used to isolate the obsolete bridge and divert the streamflow. With traffic diverted, 65 feet of 40’ sheets were driven to form a box to permit the dry installation of the new precast 10’ box culvert and cast-in-place wing walls.
In Spring 2019 NSI constructed 2 adjacent cofferdams for the deep excavation of contaminated soils at a former gasoline station. The extensive contamination and the instability of the silty clay soils required a pair of sequential 32 foot deep excavations. In the design 45’ sheets were installed along with multiple level of bracing and hydraulic megabraces.
In the end nearly 10,000 cu yds of contaminated soil were excavated and delivered to a thermal treatment site.
NSI was hired to remove 45’ steel sheets from a former contaminated soil site. In place for over year, the sheets permitted the removal of a deep contaminated layer. After a year in place, the sheets acquired a thick layer of Boston clay that had to be scraped by hand by the NSI field staff.
