4 Key Certificates of Completion in Brownfield Cleanup Program
May 04, 2022

2021 was an impressive year for the number of Certificates of Completion (COCs) in the New York State Brownfield Cleanup Program (42), and the number of Sites that SESI completed (4), two (2) of which obtained unrestricted Track 1 clean-up. Unrestricted remediation COCs are obtained when a site is remediated to the strictest clean-up objectives and results in a property without any environmental restrictions or monitoring. Most clean-ups require certain continued testing and remediation, and unrestricted COCs are rarely accomplished.

Geotechnical and Environmental Collaboration, New Rochelle

SESI completed two projects in New Rochelle: 11 Garden Street received an unrestricted COC and impressed the client with how efficiently SESI worked to get the project completed in a relatively short timeframe, and 10 Commerce Avenue received a conditional Track 1 COC. The 10 Commerce project was a combined effort between the Geotechnical and Environmental teams at SESI. The project execution was complex because of unexpected geotechnical and environmental conditions. Six underground storage tanks were uncovered during the construction and were hidden under an existing 2- to 3-foot structural slab. The geology at the 10 Commerce site consisted of bedrock of variable depth and quality, which resulted in variable rock removal depths to provide support of the proposed building foundations. In addition, the site location is at a low point relative to the surrounding areas, which resulted in significant water accumulation during the very wet winter season of 2021. The cooperative work of the geotechnical and environmental teams resulted in quick solutions to complete the excavation with the proper dewatering and an appropriate temporary support of excavation (SOE) system for the proposed building.

Peekskill Environmental Project

The third project, located in Peekskill, was touted by Former Governor Andrew Cuomo. It is 100% Affordable Housing and part of the $20 billion five-year affordable Housing Plan administered by New York State Homes and Community Renewal. The unrestricted Track 1 COC, not commonly issued by the New York State Department of Environmental Conservation, marks years of cooperation among all engineering departments at SESI. The environmental, geotechnical, and site civil teams collaborated to make this challenging project a great success.

From start to finish, the SESI team worked together with the client and rest of the design team to address each obstacle as it arose. Elevation changes of over 50 feet within a 120-foot width of the site presented challenges that SESI engineers overcame with creative solutions. Initially, SESI performed a geotechnical and environmental investigation at the Site to develop the required subsurface information for site preparation and foundation support and to obtain samples for environmental testing. The Geostructural team developed an SOE to conduct safe excavation of the contaminated soils at the Site and to achieve the required footing subgrades. The permanent excavation support system consisted of a combination of a soldier beam and lagging wall and a soil nail wall designed and inspected by SESI. The Geotechnical department designed the on-site retaining walls and steep slopes required to construct the project. In, addition, the Geotechnical team worked with the Environmental team to provide construction oversight for all environmental and geotechnical aspects of the project including Stormwater Pollution Prevention Plan inspections and reports, SOE installation, footing subgrades, retaining walls, steep slopes, utilities, compacted fills, contaminated soil removal and manifests, vibration monitoring and Community Air Monitoring Plan monitoring.

The Environmental team produced remedial plans that resulted in the removal of the contaminated soil of the site media, including soil, groundwater, and soil vapor. In the end, we delivered to the client an unrestricted Track 1 clean-up COC, the highest and most rigorous clean-up.

Geotechnical Project, New Rochelle

The final project was the most complex: a two-tower project on Centre Avenue in New Rochelle, NY. The portion of the property under construction for the first tower was approximately 100 feet by 200 feet and was the site of a former metal plating facility. This site is transformed into a $100 million mixed-use, high-end apartment and commercial space. The site contamination was found in the site soils, groundwater, and soil vapor. The site soils were excavated to Track 1 cleanup standards. The groundwater contamination was limited to southern half of the site and included chlorinated volatile organic compound (CVOC) solvents, which are dense non-aqueous phase liquids (DNAPL), and were found in bedrock; petroleum VOCs; perfluoroalkyl substances (PFAS); 1,4 dioxane; and metals. The mix of contaminants, the site geology and the size of contaminated area resulted in major challenges to achieve the groundwater remediation.

SESI conducted an extensive program to characterize the rock formation of the Site. Rock geophysics was conducted on 10 open boreholes within the 100-foot by 100-foot contaminated area. In addition, the SOE required rock cores to further understand the rock fractures and the water flow within the gneissic bedrock that underlies the entire site.

SESI designed a network of injection wells based on the rock characterization and the direction of the fractures within the competent rock. Several in-situ injection technologies were considered to treat the mix of contaminants. It was determined that the optimal remediation would consist of two programs: In-Situ Chemical Oxidation (ISCO) injections inside the site to destroy the CVOC, petroleum VOCs and 1,4 dioxane, and adsorption injection of colloidal liquid activated carbon (PlumeStop©) at the site boundary to adsorb the PFAS and metals. Two rounds of base activated persulfate ISCO were applied using two injection approaches: high-pressure pumping and gravity-feed. The result of the high-pressure injection was that the water found the path of least resistance and missed the DNAPL-laden veins. Using gravity-feed, the water was able to penetrate the rock as needed to provide the desired treatment. The ISCO injections were completed within six weeks and resulted in complete destruction of the petroleum VOCs and 1,4 dioxane and 98% reduction of the CVOC DNAPL. The PlumeStop resulted in significant decrease of the off-site impacts of PFAS, metals and VOCs. As a result, the site received a conditional Track 1 clean-up COC, and, based on the results, it is expected that the clean-up will achieve unrestricted status within five years.

SESI’s Geotechnical team also was involved in the project, providing the full-time construction oversight during the foundation construction. The highly variable depth and quality of the bedrock resulted in field modifications to alter the bearing capacity so the structural engineer could provide updated footing sizes and reinforcement on extremely short notice so that these changes did not interrupt or delay the project schedule.

SESI does not shy away from complex projects and leverages the experience and ingenuity of all departments to find the right solution for the client. Our creative approach to every aspect of the project yields solutions that can save significant time and money, resulting in projects completed on or ahead of schedule and within budget.

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