Preliminary Assessment and Site Investigation of Parking Deck

Hatch Mott MacDonald was originally retained by Essex County to perform a Preliminary Assessment and Site Investigation on a parking lot that services the New Courts Building/Hall of Records complex in Newark, NJ.  The County proposed to construct a three-level parking deck facility over a portion of the existing parking lot to increase parking capacity.  The existing lot was bound by roads to the north, south, east, and west.  Prior to its use as a parking lot it appears to have been used primarily for residential purposes; in addition, a few institutions such as a “Home for the Aged” were identified in this block on an old tax map.  Primary concerns during construction included the discovery of former heating oil underground tanks, contamination from former property operations, buried demolition debris, and contaminated historic fill imported to the site prior to its use as a parking lot.

HMM worked closely with the Essex County Department of Engineering to evaluate the site environmentally, minimize the amount of contaminated soil to be removed and disposed, and use the site development features as a cap. Soil was re-used between footings, beneath the lowest ramp structure of the garage, and as grading material below the asphalt of the re-paved parking lot.

Project Highlights:

• Performed soil sampling for contamination in conjunction with preliminary and secondary geotechnical borings in order to more rapidly characterize soils
• Consulted on foundation design and site final grading levels to minimize excavation of contaminated soil, and to consider upgrading foundation strength in order to allow for additional parking levels at a later date
• Developed a comprehensive soil handling plan for inclusion within the County’s bid specifications to allow for different pricing and handling of clean, non-hazardous contaminated, and hazardous soils
• Provided on-call specialized construction management service to evaluate suspect debris, staining and odors encountered during excavation, including the discovery and removal of several long-abandoned heating oil underground storage tanks
• Performed takeoff calculations to minimize the amount of contaminated soil requiring offsite disposal