Nosy Neighbor: Why is the water at 250 Water green?

V. sent the picture above of the full-block construction site of the tower at 250 Water and wrote: Can you find out why the water at the construction site is green?

As we know, this site was once a thermometer factory and mercury was long ago found in the soil. As a result, it is part of the state’s Brownfield Cleanup Program to ensure the protection of the environment and the people surrounding the site, including Peck Slip School on its north. The state’s Department of Environmental Conservation is overseeing the site. This is the agency’s response to the green water query:

“The 250 Water Street site cleanup was divided into two phases. Phase I was completed in October 2022. This phase included the excavation and off-site disposal of mercury impacted soil, deeper excavation of petroleum impacted soil and PCB impacted soil that exceeded Soil Cleanup Objectives (SCOs), and removal and off-site disposal of petroleum storage tanks, fill ports, and vents.

“Phase II, the final phase of remediation, is currently underway and anticipated to be completed by January 2024. This phase of cleanup includes the excavation and off-site disposal of historic fill and contaminated soil that exceeds SCOs and the treatment of onsite groundwater.

“The water in the photo is a combination of rainwater from Friday’s (Sept. 29) storm and clean grout from the soil mix operation at 250 Water Street. As part of the soil mix operation, clean grout and hydrant water are injected through the drilled boreholes until excess grout is observed coming out of the hole to ensure each column is sufficiently filled for solidification. The ‘green’ color is attributed to grout mixture, similar to concrete, which does not represent a concern for additional contamination.”

More from the DEC fact sheet, which explains the key components of the remedy:
• Excavation and off-site disposal of approximately 21,700 cubic yards of historic fill and contaminated soil across the site that exceeds Restricted Residential Use Soil Cleanup Objectives (RRSCOs);
• Excavation and off-site disposal of an area of mercury-impacted soil located in the former thermometer factory footprint to depths ranging from 4 to 16 feet below grade surface (bgs);
• Removal and off-site disposal of any petroleum storage tanks, fill ports, and vents, and any associated grossly contaminated soil, if encountered;
• Installation and operation of a dewatering system, including treatment as required;
• Importing clean material that meets the established Soil Cleanup Objectives for use as backfill;
• Collection and analysis of end-point soil samples and post-remedial groundwater samples to evaluate the effectiveness of the remedy;
• Perform a post-construction soil vapor intrusion evaluation, including a provision for implementing actions recommended to address.