Groundwater Engineering/Modeling forms a core technical practice at SHA. The following key services are provided: Analytical and Numerical Groundwater Flow and Chemical Transport Modeling Geochemical Analysis and Modeling Vapor-Phase Contaminant Transport Modeling Single- and Multi-Phase Flow Pump Testing and Analysis Subsurface Injection and Leaching Analyses Basin Infiltration and Groundwater Mounding Analyses Construction Dewatering System Design and Evaluation Groundwater Interception and Drainage Design Well Hydraulics and Well Design Typically, these technical services support analysis of groundwater flow systems, as well as analyses of subsurface chemical transport, and design of remediation systems to mitigate potential human and ecological impacts associated with the presence of subsurface chemical contamination. Examples of environmental applications include analysis and design of hydraulic containment extraction well fields to control subsurface contaminant migration, and analysis of groundwater extraction rates for the purposes of sizing groundwater treatment systems. Examples of geotechnical applications of these services include design of large scale dewatering systems for foundation construction and general excavation dewatering.

Vapor Transport and Vapor Intrusion Modeling Various Chlorinated Solvent Sites New England and Mid-Atlantic Region

Through experience in vapor migration studies dating back to the 1980s and work in subsequent vapor intrusion investigations, testing, and building mitigation projects, including one of the largest projects in the U.S., SHA brings unique expertise in modeling of vapor transport. Such modeling may be conducted to screen sites for vapor intrusion potential, to select or prioritize buildings for subsequent testing, or mitigation. Unique experience that can be brought to bear on such projects include: Modeling of vaporization and attenuation of an aromatic solvent plume conducted in the late 1980s; Proven performance in development and application of scientifically defensible vapor intrusion investigations from projects involving single buildings, public school buildings, and assignments involving hundreds of properties under residential, institutional, and commercial uses; Physical and quantitative characterization of vadose zone conditions and processes: SHA professionals offer academic training and project experience in characterization of multiphase processes in porous media as applied to model parameterization; and Monitoring of vapor conditions: SHA's experience in development and execution of long-term soil vapor monitoring programs has yielded unique insights into vadose zone processes and time-varying vapor intrusion potential.

Flow and Transport Modeling Industrial Site - Vermont

SHA was retained to construct and apply a parametric model to numerically simulate the flow and transport of dissolved-phase organic constituents related to industrial processes. SHA utilized Visual MODFLOW™ to simulate groundwater flow conditions approximating the apparent lateral hydraulic gradients observed from an existing groundwater monitoring network and a range of hydraulic aquifer properties based on site characterization. MT3D99™ was used to simulate advective solute transport of key organic constituents in consideration of the possible effects of physical/chemical sorption, biochemical degradation, and variable hydrodynamic dispersion. The modeling effort included a sensitivity analysis performed to assess the potential range of groundwater transport distances and times to peak concentration considering the apparent variability of aquifer properties and uncertainties with physical and chemical properties pertinent to the modeling objectives.

Numerical Groundwater Modeling and Capture Zone Assessment, Groundwater Extraction and Treatment Operations Confidential Client, Virginia

SHA developed and applied a three-dimensional numerical groundwater model to simulate groundwater extraction operations conducted to aid in managing the presence of volatile organic compounds (VOCs) in the regional fractured bedrock aquifer. Since the mid-1980s, groundwater extraction and treatment operations have been conducted to manage a two-mile long plume of chlorinated ethenes extending from an industrial facility to public water supply wells in fractured sandstone and siltstone of the Culpeper Basin. The goal of this modeling effort was to aid in assessing the possible relative effects of groundwater withdrawals from existing extraction wells and from potential new locations, focusing on increasing the potential for enhanced extraction of groundwater proximate to source areas, while limiting or controlling hydraulic gradients conducive to off-site migration. The active model domain covered approximately 25 square miles or approximately 16,000 acres. In consideration of available monitoring well data, production well screened intervals, and regional groundwater flow patterns; the model area was divided vertically into six layers ranging in thickness from 100 to 225 feet. The groundwater flow model was calibrated to average groundwater levels measured at 72 locations throughout the model domain and withdrawal rates for six pumping centers. The modeling resulted in implementation of recommended operating level targets and probable groundwater extraction withdrawal rates intended to reduce hydraulic gradients conducive to spreading the VOC presence in groundwater. A new groundwater extraction well sited on the basis of the modeling effort was found to substantially improve near-source containment and allow for operating levels below that observed for off-site water supply production wells.

Hydrogeolgic Evaluation Groundwater Discharge Permit - Cape Cod, Massachusetts

SHA was retained to complete a hydrogeologic evaluation in support of our client's application to modify their existing groundwater discharge permit to accommodate an incremental increase in design flow from 80,000 gallons per day (gpd) up to 275,000 gpd. As part of this effort, SHA utilized Visual MODFLOW™ to develop a three-dimensional, numerical groundwater flow model to aid in assessing the general direction and flux of groundwater flow beneath the site to evaluate the hydraulic response of the aquifer to the increased groundwater discharge. The objective was to integrate available site data including groundwater and surface water levels, surface water discharge, and subsurface hydraulic properties into a numerical analog of the conceptual hydrogeologic model developed for the site. Potential surface water impacts to an on-site pond and nearby river were evaluated under several groundwater discharge scenarios using the companion codes, MODPATH™ and Zone Budget™. Based in part on our hydrogeologic evaluation, and regulator meetings in which we participated with our client, the application to modify our client's exiting groundwater discharge permit was approved by the MADEP.

Hydrogeologic Evaluation, Proposed Quarry Expansion Litchfield, New Hampshire

SHA was retained to assess the potential hydrogeologic effects associated with expanding a hillside quarry operation by excavating approximately 250 feet below the elevation of nearby streams and wetlands over an area of approximately 100 acres. In particular, SHA focused on the potential effects on nearby residential bedrock groundwater supply wells and on the surface water and wetlands ecology that could potentially result from dewatering the excavation. SHA coordinated and assisted with the installation of 14 bedrock monitoring wells, 10 overburden monitoring wells, 8 hand driven wetland well points, and 8 stream gauges. Hydraulic testing included a one-day step drawdown test, an eight-day pumping test, dual-packer testing of bedrock wells and geochemical and radiological characterization of bedrock and overburden groundwater and surface water samples. SHA developed a quasi-three dimensional groundwater flow model, calibrated it to pump test conditions, and used it to predict groundwater conditions under various stages of the quarry development. SHA also developed a long term hydrologic and wetlands monitoring program, and made multiple presentations and appearances at public hearings. The project was successful in helping our client obtain the required local planning approval.

Hydrogeologic Investigations and Aquifer Renovation Clinton County Landfill - Schuyler Falls, New York

Several hydrogeologic studies have been completed at this landfill site in support of landfill expansion applications. Hydrogeologic characterization work was completed to assess both water quality conditions and potential impacts to groundwater levels which would result from reduction in groundwater recharge associated with construction of the landfill expansions. As part of this work, a finite difference (MODFLOW) computer model was developed and used as a predictive tool to assess hydraulic conditions beneath and in the vicinity of the proposed landfill expansion. On the basis of this work, the expansion application was approved by NYSDEC.

Characterization of Impact to Groundwater from High pH Lime Solids and Wastewater Lagoons Lime Production Facility - Massachusetts

SHA evaluated potential impact to groundwater from high pH process water lagoons. Based on assessment of site hydraulics and geochemistry, the source of high pH (up to pH 13) impacts to groundwater was determined to be largely lime [Ca(OH)2] solids present in the area of the lagoons, and not the lagoon process water. Potential impacts to deeper aquifer and adjacent stream were modeled hydraulically and geochemically. SHA conducted a pump test on a new water supply well and developed conceptual remedial alternatives.

Comprehensive Remedial Investigation, Risk Assessment, Feasibility Study, Remedial Design and Implementation Hydrocarbon and Solvent Handling Facility - Midwest, US

SHA investigated the extent and fate of hydrocarbon and solvent contamination originating from a facility used for shipping, handling, and bulking hydrocarbon products, including 140,000 gallons in underground storage and 1.3 million gallons in above-ground storage. The facility has also been used historically for handling chlorinated solvent products. A feasibility study was completed to evaluate potential remedial options for soil, groundwater, and free product at the site. Modeling of free product and groundwater extraction using the numerical models ARMOS and visual MODFLOW was completed. The feasibility of source area mitigation and various groundwater treatment technologies were also assessed. Technologies considered for soils included excavation, capping, and soil vapor extraction (SVE)/sparging. Technologies considered for groundwater included reaction walls, and extraction and treatment (including carbon adsorption, UV-oxidation, and air stripping). Various options for treated groundwater discharge were also considered. Separate oil and groundwater recovery, versus total fluids pumping and oil/water separation were evaluated. The need/extent of pretreatment for iron, manganese, and hardness was also considered.

Wellfield Management Modeling, Groundwater Supply Manufacturing Facility - New York

SHA is providing technical assistance in management of water supply well fields serving a large industrial facility with about 4 million gallons of water per day. We developed and implemented a three-dimensional numerical groundwater model to simulate production well withdrawals from about 6.5 square miles of regional carbonate bedrock and surficial sand and gravel aquifers tapped by 20 water supply production wells organized in four wellfields. The calibrated model served as an operational tool to aid in assessing the relative effects of water supply withdrawal alternatives on groundwater levels and flow directions.

Dewatering System Design, Steel Mill Northeast Ohio

SHA's assistance was requested in determining the volume of groundwater that would be required to drop the groundwater table 10 feet at a steel mill construction project, where project specifications required construction of foundations systems "in the dry." After field work to obtain site-specific information regarding hydraulic characteristics of subsurface soils, SHA employed a numerical model which was developed and calibrated to meet site-specific groundwater flow characteristics. The results of modeling efforts indicated pumping withdrawals in excess of 10,000 gallons a minute would be required to maintain the required 10-foot groundwater dry down period. Dewatering wells and discharge structures were subsequently specified and permitting requirements were identified. Using this information, a contractor subsequently successfully executed the dewatering project.

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