Site Characterization

Site CharacterizationEWI associates work closely with our clients to define an overall approach to site characterization needs, objectives, and constraints based on the applicable regulatory framework. We use an array of proven and innovative sampling techniques and equipment to investigate environmental problems, including the nature, extent, fate, and migration of contaminants in environmental media. Site characterization services provided by EWI often include:

  • Strategic planning and agency negotiation
  • Development of data quality objectives and work plan preparation
  • Remote sensing and interpretation
  • Soil gas surveys (passive and active sampling techniques)
  • Hydrogeologic investigations
  • Nature and extent determinations in soil, sediment, surface water, and groundwater
  • Monitoring well installation and sampling (passive and active techniques)
  • Aquifer testing and analysis
  • Groundwater modeling
  • Solid 3-D modeling
  • Vapor intrusion evaluation and modeling
  • Real-time analysis of data
  • Data validation
  • Statistical analysis
  • Data management and reporting
  • MIP Techniques

Subsurface Imaging & Modeling

Using innovative subsurface imaging and modeling technologies to characterize a site, saves our clients a substantial amount of money—millions of dollars in future remediation costs on some projects. They also allow us to better assess projects and develop strategies without the guesswork. This is key in extremely complex hydrogeology projects.


Environmental Works, Inc. (EWI) is contracted to continue remediation activities for a multi-million dollar CERCLA/Superfund/NPL project site operating under Consent Decree.

The Site has been under remedial operations since 1993 to clean up a chlorinated organic contaminant plume in karstic and fractured bedrock. Previous investigation by the State had identified a former circuit board manufacturer as the source of the contamination, namely trichloroethylene (TCE) and its degradation products, which had been detected in the City’s public water supply wells.

The extremely complex hydrogeology, which underlies the location combined with a DNAPL source makes it one of the most complex sites in the State of Missouri. EWI managed operations of a groundwater pump & treat system until 2011.

Since 2009, EWI has worked with the MDNR to develop an interim remedy under the Innovative Technologies option provided by the Consent Decree. The use of innovative technologies has the potential to save the client millions of dollars in future remediation costs.

EWI became the prime contractor on this site in 2006, and has since expanded management responsibilities to include evaluation of alternate remedial strategies and implementation of performance based environmental management practices to work toward risk-based closure of the site, including an initial evaluation of exposure pathways (vapor intrusion) not previously addressed at the Site.

EWI has taken initiative by negotiating alternate remedial actions on behalf of the client to MDNR and EPA resulting in the treatment of approximately 2,500 yd3 of TCE-impacted soil via chemical blending with pounds of potassium permanganate. Blending activities were performed by EWI personnel and equipment from approximately 6 feet below land surface (ft bls) to the top of bedrock (~20 ft bls) and in close proximity to several groundwater monitoring wells. Negotiations are currently ongoing with regard to the treatment of additional TCE-impacted soil located beneath a main street and several utilities adjacent to the site.

EWI has provided technical documentation supporting alternate cleanup standards and / or alternate remedial action and implemented solutions, while continuing to maintain compliance with strict state and federal regulations and project performance criteria.


Chlorinated solvents were detected in an industrial well open to a regional drinking water aquifer, located at a former dry-cleaning facility.

A downhole video survey indicated that groundwater contamination was likely a result of impact within a shallower hydrogeologic zone. To investigate the extent and source of the compounds, innovative characterization activities were performed within shallow unconsolidated materials and shallow bedrock, which contains a cave, solution conduits, and various fracture features below the water table.

Characterization activities performed include the following:

  • Completion of passive soil gas survey, including 44 monitoring points over an approximately 75,000 ft2 area
  • Advancement of 19 borings and 7 temporary monitoring wells, targeted to areas of solvent impact as indicated by the soil gas survey
  • Completion of a specialized geophysical resistivity survey to identify potential areas of impact, preferential migration pathways, fracture zones, and/or important lithologic features
  • Installation of 8 shallow bedrock monitoring wells by sonic drilling to evaluate anomalies identified by the geophysical survey and the dissolved-phase plume at the site
  • Downhole videography to evaluate karst features

Due to the high profile nature of the site (high-traffic public park), the activities outlined above were completed within an aggressive six-month period that required meticulous care for minimal damage to park grounds. Data collected from characterization activities were utilized to develop an initial site conceptual model as part of the Missouri Risk Based Corrective Action (MRBCA) process.

EWI personnel and equipment were utilized to perform soil gas survey, install borings and temporary wells, and downhole videography. EWI geologists and scientists worked with the geophysical survey subcontractor in evaluating geophysical results and determining appropriate bedrock monitoring well locations, and performed sonic drilling oversight and detailed logging of continuous core samples.

Planned activities for this ongoing project include closure of the industrial well, modification of a monitoring well intersecting a large cave, installation of additional bedrock monitoring wells, sampling, and dye tracing studies.


A major pipeline company contracted Environmental Works, Inc. (EWI) for emergency response cleanup, then follow-up site characterization and remediation after a release of diesel fuel, gasoline, and jet fuel from an underground pipeline.

The release entered the subsurface, traveled downgradient, and resurfaced with seepage of product impacting 19,000 square feet of land. EWI performed free product control and cleanup, recovered 260 gallons of free product, excavated 1,600 tons of petroleum-impacted soil, and containerized 42,500 gallons of petroleum-impacted surface and excavation water. Associated wastes were characterized and properly disposed. This work was completed within 78 days of the release discovery.

The site was subsequently entered into the MDNR Voluntary Cleanup Program (VCP). EWI performed a site characterization and a detailed hydrogeological investigation that included:

  • Mapping surface karst features (sinkholes, springs, fractures, etc.)
  • Photo-lineament interpretation to identify prospective fracture zones
  • Geophysical resistivity transects to pinpoint fracture zones
  • Stream survey to identify potential groundwater discharge points
  • More than 150 soil borings to verify subsurface conditions
  • Extensive soil sampling and groundwater chemical analyses
  • Installation of twelve 6-inch diameter, open borehole unconsolidated and bedrock wells up to 70 feet deep and four soil vapor monitoring points
  • Multiple dye tracing studies to support remediation planning

EWI established ongoing well and subsurface product recovery systems, and performed innovative, interim in-situ oxidation treatments using the karst network, while completing site characterization work to hasten the remediation timeline.

EWI performed the majority of the emergency response and characterization work using in-house personnel and equipment. Soil borings and piezometers were drilled and installed using direct-push equipment (Geoprobe®) owned and operated by EWI.  EWI Missouri Registered Geologists and technical professionals also performed all mapping, lineament and fracture interpretation, stream survey monitoring, and hydrogeological evaluations.  EWI teamed with Missouri State University for additional technical services and geophysical interpretations.  EWI consulting services also included project coordination and direct communications with the MDNR Division of Geology and Land Survey officials.

  • EWI served as the successful replacement to initial response contractor that could not meet challenging technical objectives.
  • EWI successfully contained product releases and prevented surface migration to the local creek.
  • EWI has maintained all characterization activities well within the planned and approved budgets and accomplished bedrock drilling at a cost savings of over $10,000 to the client.
  • Successful contaminant delineation despite complicated geologic and hydrogeologic conditions – e.g. sinkholes, horizontal voids and fractures.
  • Continual product recovery and intermediate ISCO treatment while completing site characterization.