Hamp, Mathews & Associates (HMA) provides engineering design and build services for environmental remediation and green stormwater infrastructure (GSI). Using a fundamental risk-based corrective action (RBCA) approach, HMA bases design/implementation needs on a synthesis of site environmental data and the source-transport-receptor interrelationships known as the Conceptual Site Exposure Model (CSEM). The CSEM creates a “road map” for the project and sets the bar for design/build needs.
From a remediation perspective, HMA is versed in both ex-situ and in-situ technologies. With the CSEM firmly in view, we follow an unbiased technology screening and feasibility study process to weigh technical and economic efficacy and appropriateness across a wide variety of physical, chemical, and biological techniques. Our designs are intended to accomplish the project remediation objectives (ROs) with optimal resource utilization. These remedies span the spectrum of complexity and scale in relation to the project ROs and CSEM. A few examples for soil, water, and air are highlighted below.
In-situ Stabilization/In-situ Oxidation (ISS-ISCO) for Tetrachloroethene (PCE) in Clay Soils
ISS-ISCO (of PCE in clay) is a fusion of two acknowledged technologies to achieve both contaminant mass degradation via rapid oxidation reactions and PCE mobilization reduction via stabilization. At a dry cleaner site in Lansing, the CSEM necessitated that a nearly half-acre source (approximately 15,000 CY) of heavily contaminated soils required active remediation to remove/reduce the source of a soil vapor plume affected adjacent properties. To accomplish this goal with optimal resource allocation, HMA designed and implemented an ISS-ISCO approach which coupled the degradative benefits of sodium persulfate oxidation with the stabilization benefits of Portland cement stabilization. This approach met the RO with a cost savings of over $2 Million compared to traditional excavation. More details can be found here Design Strategies and Applications Combining ISCO and ISS.
Physical removal of contaminated soil and associated transport and disposal to an approved disposal/re-use facility is an established and effective contaminant source remediation practice. In some cases, excavation offers a quick and efficient opportunity for source removal, which may help minimize long-term downgradient costs. Depending on the site setting and ROs, the application of this technology can range from simple to complex (e.g., dewatering, trenching, and shoring, sheet piling, etc.). Key to the design/implementation of this technology is navigation of the waste characterization/approval processes, which HMA is versed in for a wide variety of contaminants including chlorinated solvents, petroleum hydrocarbons, PCBs, metals, and asbestos.
Sparging is a technology intended to remediate source area soil and groundwater contaminated with volatile organic compounds in which a gas is distributed into the contaminated saturated zone beneath or at the base of the contamination and allowed to distribute horizontally and vertically out through the contamination. This technology leverages the physical disruption caused by this activity and the volatility of the contaminants to cause physical mass transfer from aqueous to vapor phase. In addition, the addition of this gas into the zone often creates a favorable environment for biological degradation. For example, for chlorinated ethenes such as PCE and TCE, HMA is currently performing a Nitrogen sparging pilot study in a residual source area at a chemical manufacturer (see Case Study #). HMA also utilized sparging in an innovative way for plume management via “Sparge Gates” at a petroleum refinery.
Bioremediation involves chemical degradation via microbial activity. These destructive microbially mediated transformations can be metabolic (meaning they are performed as part of the microbes’ basic metabolic actions) or co-metabolic, which means the degradative or destructive transformation is a result of fortuitous microbial activity but is not a basic, metabolic function of the microorganism. While bioremediation transformations can be kinetically slow (compared to chemical reactions), biological treatment is well-suited to in-situ applications and can frequently be a low cost, low energy, and low footprint option compared to physical and chemical treatment technologies. Biostimulation involves the stimulation of indigenous bacteria or microorganisms already present at a site, while bioaugmentation involves the addition of bacteria at a site (typically because they are not present or present at an inadequate level). HMA has been a long-time practitioner of bioremediation, with vast experience in bioremediation of both chlorinated solvents and petroleum hydrocarbons.
Typical indoor air projects are time critical. Often, homeowners may be displaced and/or a regulatory agency requires rapid volatilization to indoor air pathway (VIAP) mitigation to eliminate potential receptor exposure. HMA performs turnkey services with regard to design and implementation of vapor mitigation systems (VMSs). These can range from passive vapor barrier systems for new construction sites to retro-fitting sub-slab depressurization systems (SSDSs) at existing structures. HMA performs their own system design, which typically involves diagnostic testing across the building footprint. HMA also performs their own system installation for SSDSs, including suction pit construction, plumbing, and mechanical construction. Retro-fitting these systems in unique existing structures often present pressure field extension challenges; HMA’s detailed diagnostic testing often leads to custom systems fabricated to overcome structure or geology specific obstacles. HMA has a suite of licensed electricians across the State from which to utilize for final hookup of systems. This turnkey approach allows for more effective and timely achievement of indoor air (VIAP) remedial objectives and management of potential receptor exposure.
HMA provides a comprehensive suite of Compliance services to the regulated community. These services are important to our clients for continuity of business and services, creating and maintaining a standard of ethical business practices, and demonstrating environmental responsibility which is becoming increasingly important in today’s business landscape.
Environmental regulatory agencies apply traditional risk assessment processes to estimate an amount of chemical in the environment that could cause an adverse health outcome to humans and ecological receptors. The estimated chemical concentration is derived from scientific studies of the chemical’s toxicity combined with upper range values of exposure that a person, plant, or animal may experience.