Projects – NSI Contracting

Attleboro MGP

March 28, 2021

In 2020 NSI provided shoring for excavation of coal tar waste. During 1880-1900 Manufactured Gas Plants were constructed near cities to provide lighting gas. These plants processed coal to generate methane and produced volumes of coal tar waste. An old MGP site in North Attleboro left thousands of cu yds of coal tar and contaminated soil that needed removal and remediation. NSI was tasked to design and install cofferdams in phases for water control and excavation safety to expedite removals. In phase I & II, 2 L-shaped cofferdams approx. 160’x293’ were installed and braced with tiebacks of 80’ beams to hold river water in check on shallow bedrock.

Berlin CT – Soil Remediation

March 10, 2021

In Berlin CT – a contaminated soil removal at 30’ depth required a 36’x36’ coffer dam. The shallow bedrock and high water table required two levels of bracing to safely permit removal of contaminated soil and installation of clean fill.

Mt Tom Power Plant

March 1, 2021

The Mt Tom Power Site was the location of an obsolete coal power plant on the CT River dismantled in 2016. NSI was contracted to build two coffer dams (125’x60’x125 and 50’x25’x50) to allow the excavation and removal of the facility’s water intake and discharge piping in the river. This effort required extensive obstruction removal during sheet installation. Fifty foot sheets and two sets of steel bracing were installed to permit the dewatering and structure removal. A 250ton crawler crane was required to provide the 170’ reach for the sheet pile installation.

Rehabilitation of the Field Dam

March 20, 2020

NSI was awarded a contract to assist with the rehabilitation of a 100 year old recreational and water storage dam in the DCR Harold Parker State Park. The contract required over 500’ feet of 35’sheet piles in the main dam structure and 175’ of 15’ steel sheets in an adjacent dike as a cutoff walls. In a second phase, NSI constructed a 30x34x30 15’ deep cofferdam to construct the new low flow discharge structure. NSI performed the installations in close concert with the general contractor and the DCR design engineer. The construction was completed under approval of the Mass Division of Dam Safety and the Department of Conservation & Recreation.

Amtrak Station Westerly RI

March 17, 2020

In 2019 NSI responded to a request to design and install a cofferdam for a handicap elevator at the AMTRAK Station, Westerly RI. High voltage catenary wires required all work adjacent the tracks be conducted overnight after service had stopped. Special permanent beams and baffling were installed to form around a passenger conduit tunnel at -15’ elevation.

Reconstruction of a Seawall

March 17, 2020

In the Spring 2019 NSI constructed over 145’ feet of a replacement seawalls as part of the reconstruction of a private marina along the Charles River. The seawall was constructed of zinc coated 25’ PZ22 steel sheets braced with stainless steel channel bolted to the pile tops. The construction was completed under approval of the Army Corps of Engineers.

Soil Remediation of a Former Industrial Laundry Facility

March 17, 2020

In March 2019 NSI was contracted to construct a 200’ foot long cofferdam along a stream adjacent to a former commercial laundry. The facility had spread PCB contaminated wastes along the shoreline. The shoring isolated the affected segment between the stream and the contamination. The removal excavated over 200 cu yards of contaminated soils for proper disposal.

West River Sewage Pump Station

March 17, 2020

In September 2018 NSI was contracted to install a 30×30 28’ deep cofferdam for the installation of a new pump station. The installation had to overcome significant obstructions and a persistent high water table which required both a redesign and extensive energetic dewatering efforts. The pressures of the high water table required additional hydraulic bracing to ensure a safe excavation.

Discharge Canal Coffer Dam

March 17, 2020

An engineering firm working for Canal Electric had redesigned the discharge flume for the power station. The new design required a cofferdam to complete the installation of a new discharge pipe at the canal. NSI installed 50’ long PZ22 sheets into the canal floor forming a cantilevered cofferdam 20x50x20. The contractor sealed the edges with super sacks to complete the installation in the dry.

Rt 4 Lafayette Rd Bridge Abutments

March 17, 2020

In January 2019 NSI constructed four 40’ retaining walls at each corner of an obsolete highway bridge. The walls permitted the adjacent construction of the new bridge deck for each lane. In the Fast Bridge Program the new deck is slid into place once the old bridge lane is demolished and removed. The remove/replace sequence occurred over 48hrs in a weekend for each lane.

Archives

Attleboro MGP

Berlin CT – Soil Remediation

Mt Tom Power Plant

Rehabilitation of the Field Dam

Amtrak Station Westerly RI

Reconstruction of a Seawall

Soil Remediation of a Former Industrial Laundry Facility

West River Sewage Pump Station

Discharge Canal Coffer Dam

Rt 4 Lafayette Rd Bridge Abutments

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