HECSA Demolition of Subsurface Concrete Structure & Above Grade Perimeter Fence Removal

Our Civil Division was awarded the Demolition of Subsurface Concrete Structure & Above Grade Perimeter Fence Removal project by Doyon Technical Services and the U.S. Army Corps of Engineers (USACE). This project was located at Humphreys Engineering Center (HEC) within the 450+/- acre Research and Development tract adjacent to Telegraph Road in the extreme northern section of Fort Belvoir in Alexandria, VA. The Humphreys Engineer Center Support Activity (HECSA) is responsible for providing day-to-day installation management and support services to the Headquarters, U.S. Army Corps of Engineers and other Corps activities located in the National Capital Region.

In order for the personnel at HECSA to produce future building plans to support their mission they needed a team of qualified experts to perform much-needed sitework to an existing area they called the “soccer field”. This was not your average soccer field. Years ago, it was the site of an underwater testing facility. When the building was demolished, they used the site for waste disposal. Results of a Geophysical Survey Report in 2019 indicated there was a reinforced concrete slab beneath the surface grade of a portion of the soccer field. The concrete slab was believed to range in thickness from 8-12 inches based on a geotechnical investigation performed by the USACE.

Doyon Technical Services and the USACE trusted FTC to complete all aspects of this demolition and site rehabilitation project. The scope of work encompassed furnishing all engineering, construction labor, equipment, and materials to remove, dispose and recycle the underground reinforced concrete slab structure as well as an above grade perimeter chain link fence. Our scope of work also included the restoration of the site following removal.

Prior to the start of site clearing, the FTC Civil Division personnel had to obtain all necessary permits from the Virginia Department of Environmental Quality. Additionally, we had to submit a “Site Access and Haul Route Plan”. HECSA was operational by employees and civilians so it was imperative that all vehicles and equipment followed a strict route identified within this plan in order to not disrupt any day-to-day activity. This was especially important as we hauled out hundreds of truckloads of steel, concrete, and other debris found beneath the soccer field.

Hazardous Material
A geophysical investigation was conducted for the proposed Battalion Operations Facility that would be built on the existing soccer field. This investigation found that a wave tank structure was located within this footprint. From the investigation it was suspected that buried metallic structures and other debris such as underground storage tanks, possible unexploded ordnance (UXO), and other trash would be present. As you can imagine, this was an area of concern. FTC worked carefully and on high alert throughout the site in the event we would encounter any of the buried debris. What would’ve happened? Construction would’ve been halted due to the hazardous nature of the material and it ultimately would’ve slowed down our timeline for completion. Luckily our crew did not encounter the mentioned hazardous materials during this project.

Excavation began on February 23, 2021. The first stage of this process was to test pit as needed and excavate down to the existing concrete slab which was approximately 8 feet below grade. Once we reached the buried concrete slab, we used a rock hammer to break the concrete into pieces in order for disposal offsite. This slab was no small feat as it measured 130 ft wide, 305 ft long, and a depth of approximately 12in. It took roughly 185 truckloads to dispose and recycle the material that was extracted from the site.

Site Limitations
The entire concrete slab could not be excavated at one time because we needed room to stockpile the dirt as well as room to maneuver equipment around. In order to work efficiently, something we take pride in, FTC management designed a system that divided the site into four sections. By doing this, we were able to create a process that would allow us to excavate one area, stockpile in a different area, and then utilize that dirt to backfill. As we excavated section 1 the material was stockpiled on section 3. After removing the concrete slab under section 1, we started excavating section 2 while simultaneously using those materials to backfill section 1. Section 4 was excavated next. We utilized those excavated materials to backfill section 2. The material stockpiled on section 3 was used to backfill section 4. Section 3 was the last section to be completed using materials stockpiled on section 1. The leap frogging approach allowed us to handle the material in the most efficient way possible.

Discovery of Concrete and Steel Pit
While crews were digging in section 4 of the site plans (drawings supplied in supplemental docs), we encountered a reinforced pit that was not on the original drawings. This pit was well below the elevation of the existing concrete slab. All work was paused in order to identify the structure and determine next steps for a safe removal. The pit measured 35ft wide x 45ft long x 6.5 ft deep. It was constructed of concrete columns and steel I-beams. Not only was this pit filled with an extensive amount of debris, it contained an unanticipated amount of groundwater.

We knew backfilling the pit would take more than the best dirt onsite to meet compaction requirements. Ultimately, after suggestion from FTC, a change order to install a bridge lift with filter cloth and stone was agreed upon. The crew worked to backfill the site with the appropriate materials to meet the desired grade.

After successfully removing and recycling the debris from the concrete slab, we tackled the removal of 1,300 LF of the 5 ft tall chain link fence that was along the perimeter of the site. Once removed, we backfilled the post holes and additional disturbed areas to stabilize the ground in accordance with the guidelines set forth in our contract.

As part of our contract, Ferguson Trenching was to provide vegetative stabilization in compliance with all erosion and sediment control and stormwater management requirements. Those requirements meant we had to have at minimum 75% grass growth over the 125,700 SF (just under 3 acres) field before completion. Summer of 2021 was extremely dry. Thus, making this goal less obtainable. However, FTC always has a solution.  We utilized one of our water trucks onsite for many weeks in order to fulfill the specifications.

We wrapped this project up in September of 2021 after the final blades of grass were established. In the process of this project, FTC recycled 4,537,036 pounds of concrete and 88,540 pounds of steel from the site.

This project was no small feat for our four-man crew. These gentlemen worked five 10-hour days to get this job complete in a timely manner. Due to the location out of state, we provided them with accommodations during the week to not impact timeline as well as their health. Our leadership emphasizes safety and quality day in and day out. It’s important to us that our FTC family remains healthy and safe.

Kudos goes out to Foreman Jamie Knotts and crew members Rodney Haines, Amaro Arreguin, and Robert Davis for their hard work and dedication to this project!

2022 ABC Chesapeake Shores Excellence in Construction award winner!

Pictured left: FTC Civil Division Foreman Jamie Knotts
Pictured right: ABC Chesapeake Shores Chairman Mike O’Quinn