The area of the former gas production plant "Clifton MGP OU-1" is located at 40 Willow Avenue, Staten Island, a borough of New York in the Richmond County. On this area were located the gas holder and supporting facilities of the plants. When the structure was demolished the basement - a circular brick basin of the 85ft diameter (26m) - was left in place and buried. Over the years the pollutants present - hydrocarbons and heavy metals - have begun to filter and end up polluting the groundwater.
2006 | 2009
The aim of the work was to stop the migration of pollutants present in the soil. To do this the project involved the construction of a cutoff wall placed in adherence beside a single row of metal sheet piles driven into the ground.
The treated soil is quite heterogeneous and includes more superficial anthropic layers, composed of fill material, alluvial layers formed by sands, gravels, silts, clays and peat variously mixed and interspersed, a layer consisting mainly of morainic debris of glacial and fluvioglacial origin and, in the deepest layer, altered bedrock of schist origin.
It's easy to see the jet grout containment barrier wall was installed through very challenging ground conditions: boulders, flowing sand and artesian water at a pressure of 44 psi (0.3 MPa) were present.
A total of 126 columns with a diameter of 6 ft (1.8 m) and a length of 98 ft (30 m) were required for the construction of the 126 m long Jet Grouting barrier. All Jet Grouting treatments were installed using a double-fluid technology PS2W (water and grout) and bottom-up installation procedure.
Given the state of high hydrocarbon pollution of the site, equipment and methods were used to recovery polluted injection fluid (preventer directly placed on the concrete slab, watertight tank and suction pump) to allow transfer to treatment areas without leakage and avoiding contact with workers.
Continuous monitoring of Jet Grouting parameters using PRS3 real time data collection system and vertical measurement at each grout column were provided as well as extensive verification and field test prior to the production work.
