Contaminated Soil Remediation by Excavation
Contaminated soil remediation by excavation is a common environmental clean-up method at construction sites with ample space. When site conditions permit and contamination is shallow, geologists and excavators can replace the contamination area by importing clean fill. Contaminated soil remediation by excavation is ideal at spacious sites. Additionally, this method prefers smaller contamination plume-areas, and mainly heavy-oil or metal-base chemicals of concern. For example, a vacant field, with a used-oil spill area, which spans roughly 30 feet wide by 10 feet deep. However, excavation methods are hardly functional in circumstances where groundwater contamination is apparent. Moreover, if the extent of contamination is deeper than roughly 15- to 20- feet, excavation may not be a feasible remediation method. During the environmental site assessment phase of work, engineers and geologists formulate the lateral and vertical extent of contamination, to determine the most applicable methods for remediation. Updated December 30, 2019.
Environmental Site Assessments Before Excavation
The complete lateral and vertical extent of a contamination plume is a prerequisite of the excavation remediation process. This information becomes obtainable during a series of subsurface investigations. For example, data from a Phase II Environmental Site Assessment can assist geologists in understanding subsurface conditions. However, additional site characterization may be a requirement in furtherance of a Phase II ESA report. In fact, a Phase II ESA report rarely provides enough data to fully define the extent of the plume. Instead, it serves as a limiting investigation to determine if any contamination exists at all.
An excavation is any human-resulting cut, cavity, trench or depression into the ground surface by removal of earth material. Contaminated soil removal by excavation can resolve multiple issues at once. For instance, a subterranean garage proposal at a shallow soil contamination plume area is an efficient plot to clean-up and develop a lot at the same time. Moreover, removing the source of toxic substances underground can be a preventative measure to safeguard future occupants from carcinogen exposure.
Groundwater contamination is not subject to remediation using excavation methods. In fact, the results of the prior environmental site assessments should provide insight as to whether groundwater contamination exists or not. If excavations encounter the groundwater table, additional permits may be required by local health departments. Consequently, additional measures (and costs) will be a requirement. For example: groundwater pumping and treatment; slurry-walling the contamination area, and groundwater sampling, and more.
Equally important to the excavation work, is the confirmation sampling. During the excavation, additional confirmation soil sample collection is necessary to verify the completion of source removal. This is a mandatory step in the remedial action process. And in most cases, a regulatory agency will ask to review the results of confirmation sample laboratory data.
Building & Grading Department Regulations
In California, excavations must comply with the safety codes and regulations of the Division of Occupational Safety and Health (DOSH), also known as Cal/OSHA. Additionally, the California Building Code (CBC) Appendix J provides guidelines on performing excavations with proper lateral support and safety. Geo Forward is an industry leader in contamination excavation and grading projects. The team has experience with various methods and applications for safeguarding onsite personnel as well as future occupants.
Furthermore, the onsite field personnel must have the appropriate hazardous waste operations certifications. And soil contamination spoil transportation require special licensing. Similarly, all disposal centers require government registration and documentation. And there is a professional requirement for geotechnical engineers to test and certify the proper compaction of back-filling materials.
The final stages of contaminated soil excavation include the legal transfer and disposal and treatment of the spoils. As a result, there is a requirement to document the generation of the spoils through an EPA Identification code. Additionally, a waste transportation manifest and disposal profile is a requirement for site closure.