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To date, we have set up safe work zones within Solomon Jacobs Park, and begun drilling an excavation support system behind the existing seawalls. Once this system is installed, we will remove the granite seawalls and the soil behind them. This process is expected to take several months, during which we will monitor air quality levels, noise levels, and vibration levels in the area.
In the harbor, barges have arrived with dredging equipment, water treatment equipment, and a large crane. We have installed environmental controls in the harbor near the park, and the dredge barges will be surrounded by similar controls when work is in progress. The first stage of in-water work will include debris removal from the seafloor, followed by dredging of contaminated sediments. The sediments will be shipped by barge to an out-of-state facility. During this phase of work we will also remove the wooden pier in front of the park to allow closer access to the seawalls, and begin drilling or driving steel beams in the water in front of the Harbormaster building.
Dredging: The project involves dredging of approximately 25,000 cubic yards of contaminated sediment from Gloucester Harbor. The permits for the project have Time-of-Year restrictions which require that dredging be completed by February 14 of each year. To date, approximately 12,000 cubic yards of sediment have been dredged and loaded into scows. The wet sediment is allowed to settle within the scow, and the excess water is pumped to a water treatment system located on another barge near the Site. The water is discharged back into Gloucester Harbor after treatment. Approximately 1.5 million gallons of water has been treated to date. The sediment is then shipped via barge to a licensed facility in New Jersey for processing and disposal. Based on the current production rates, we anticipate that more than half of the total volume will be dredged and the dredging to be performed within the channel portion of Gloucester Harbor will be completed during the first work season. This will leave the remainder of the sediment near the shoreline area of the site to be removed during the second dredging season. The second dredging season will start in July 2016 and will continue into February 2017.
Solomon Jacobs Park Seawalls: This is one of the very technically challenging components of the project: it involves constructing a deep excavation support system behind the old granite block walls, removing the outer walls and the soil behind them, and then rebuilding a new seawall along the park perimeter.
To allow access to this area for barge-mounted equipment, the timber pier in front of the park was removed in the fall 2015.
The excavation support system was completed in December and is visible from the harbor during low tide – it consists of a series of grout-filled steel piles, with steel plates below the high-water mark and wooden boards above, and steel rods connecting this system to weighted concrete blocks buried behind the plates. This support system allows the excavator to safely dig down to the depths required to pour concrete for the base of the new walls.
The concrete base of the new seawall will be almost 8 feet below the low tide mark, so much of the work must be coordinated with the tides and/or conducted under water, with divers inspecting the underwater work. As of late January, two-thirds of the concrete base has been completed, with the top surface just below the low water mark. It is anticipated that the entire concrete base will be completed, and that the bottom blocks of the granite block wall will start to rise above it, within the next several weeks.
The project is on track to complete reconstructing these seawalls by mid-May 2016. Over the next several weeks, steel piles will be installed in front of the new park seawalls to support a floating dock system for the City of Gloucester. The floats will be installed in May 2016 so that the park can re-open to use by the public in the summer.
Harbormaster Building Seawall: The project involves building a new steel-pile-supported seawall in front of the Harbormaster Building extending onto Maritime Gloucester. This task is complicated by the age and condition of the existing granite wall, the presence of the building adjacent to the wall, the limited access available for large equipment, and extremely large boulders beneath the wall and directly in front of the wall that are submerged below the floor of the harbor. Initial piles have been installed in front of the Maritime Gloucester Boat House building and in front of one corner of the Harbormaster Building. Additional piles may be driven before February 14, when work will be suspended in accordance with the Time-of-Year restrictions. Starting in fall 2016, temporary in-water supports will be built so that specialized equipment can be used to complete the wall construction during the second work season.
United States Coast Guard: The rehabilitation of USCG Pier 2 is progressing, with new cross-bracing and fender piles installed at this location. Once complete, a temporary docking system will be built in front of Pier 2. This will provide an alternative location for the Coast Guard to dock their vessels during the second work season, when the nearshore sediments on their property are being dredged.
Maritime Gloucester: For safety reasons, the area in front of the Boat House is currently restricted to remediation crew and equipment. Therefore, a new landing and stairs were built on the north side of the Boat House for access into the building, and a new landing was added to one of the finger piers to allow gig rowers continued access to the harbor. Limited pile-driving may be conducted in front of the Maritime Gloucester seawall over the next several weeks, but most of the remediation at this property will be conducted during the second work season.
Environmental Controls: The orange booms floating around each of the remediation work areas in the harbor are the tops of in-water curtains designed to control turbidity (suspended particles in the water column) and sheens generated during dredging, drilling, pile driving, and excavation. Absorbent booms at the water surface act as a sponge to collect sheens, and are regularly inspected and replaced as necessary. The underwater curtains are also inspected for snagging on underwater obstructions, and are adjusted as needed to allow them to move freely with the tides.
Throughout the work, regular readings are taken to monitor dust levels, noise levels and vibrations around the work area. The air quality is continuously monitored by an automated system of sensors to protect the safety of both the workers at the site and occupants of surrounding properties.
The Public Archaeology Laboratory, Inc. (PAL) is providing cultural resources services in support of the executed Memorandum of Agreement (MOA) for the former Gloucester Manufactured Gas Plant (MGP) Remediation Project. Read more about Gloucester’s harbor heritage, the history of the waterfront, Burnham’s marine railway, and archaeology in the harbor.
National Grid has successfully completed the first season of remediation activities, and in accordance with our agreement with the City of Gloucester, Solomon Jacobs Park and an interim City floating dock system were re-opened to the public for Memorial Day weekend. Our activities during the first season included dredging approximately 16,000 cubic yards of contaminated sediment from the harbor, removing and rebuilding the granite block seawalls at the park, and installing steel piles for the permanent City of Gloucester floating dock system that will be installed during the next work season.
During the remainder of the summer, construction activities at the park will be suspended to allow public access to the waterfront. The park and the interim floating dock system will remain open through Labor Day 2016, after which they will be closed to allow for the second phase of remediation activities. Remediation at neighboring properties has begun as part of the second season of work. In-water construction at the Maritime Gloucester property started on August 1st with the setting up of work zone controls and re-location of existing features. Demolition of the Maritime Gloucester piers will begin this week, as will dredging at the United States Coast Guard station. This work will continue through the month of August. The second season of remediation at Harbor Loop is scheduled to be completed by Memorial Day 2017.
Season 2 activities are now underway at all four properties along the waterfront. Preparations are being made to move the Coast Guard vessels from their current floating docks to an interim docking structure that is being constructed at their facility. A new temporary breakwater system has been installed in the anchorage area to support this interim docking arrangement. Once the Coast Guard vessels have been moved, dredging will begin in the nearshore area of the Coast Guard property, and the stability wedge and porewater cap will be constructed adjacent to the seawall.
At Solomon Jacobs Park and the National Grid property at 19 Harbor Loop, the current focus is on reconstructing the old seawalls to meet current safety standards. Later this month, a jack-up barge will be mobilized to the Site to install the underwater supports (piles) and foundation for a new seawall in front of the Harbormaster building.
At Maritime Gloucester, portions of the northern and southern hauling piers, as well as the decking of the Harriet Webster Pier (Main Pier), have been removed to provide access for dredge vessels. The remnants of the abandoned marine railway were removed under the supervision of a marine archeologist. Large amounts of debris that would prevent the dredge equipment from operating correctly were also removed, including rope, cable, tackle, lobster traps, chains, ladders, and tires. Over the next several months, contaminated sediment at Maritime Gloucester will be dredged using two techniques. Most of the property will be dredged mechanically, using an excavator equipped with an environmental bucket, but the area around the operating marine railway will be dredged using special suction dredging equipment that will allow the railway to stay in place throughout the process. Dredging is anticipated to last several months, and will be followed by the placement of clean backfill material and the re-installation of the various structures at the property.
Soil within the park was capped with clean fill material, and a subsurface system to recover coal tar from deep in the ground was installed and will operate automatically over the next several years until the recoverable coal tar has been removed.
As part of Site restoration efforts, docks and piers that were removed or relocated at the Coast Guard, park, and Maritime Gloucester properties have been replaced or rebuilt in kind. A new floating dock system owned by the City of Gloucester is now in place for use by the Harbormaster. Solomon Jacobs Park and the adjacent parking lot have been restored with ADA-compliant features, and the new land in front of the building at 19 Harbor Loop offers additional waterfront access and views to park visitors.