Services→Hydrogeologic→Hydrogeologic Investigations

Hydrogeologic Investigations

ENW’s Hydrogeologic Investigation Division has successfully completed highly visible water supply and water resource work. This broad-based experience in both water supply and contamination investigations is available to our clients in both the private and public sectors, including:

Groundwater Modeling

Modeling is the process of using computer simulation techniques to reproduce the hydrogeologic and environmental conditions at a site. In groundwater modeling, the processes of groundwater flow in response to natural and imposed hydraulic head differences, advection, diffusion, dispersion, chemical equilibrium, absorption and chemical decay, leakage, withdrawal, and recharge can all be described with the mathematical language of the computer program and applied to a simplified two- or three-dimensional representation of subsurface conditions. Once the simulation is considered reasonably accurate, the model can be used to test hypothetical scenarios.

ENW applies groundwater models effectively for Prediction, Aquifer Characterization, Risk Assessment, and Remediation.

Prediction
Models are used for describing groundwater flow patterns and assessing impacts to aquifers and water resources under different groundwater resource stress scenarios. Predictive models can also address future migration, expansion, and attenuation of contaminant plumes. The predictive function facilitates resource planning. ENW utilizes Groundwater Modeling System (GMS) as a base for most intricate modeling projects. GMS is the most advanced and comprehensive groundwater modeling front-end package (i.e., graphical user interface) available. The program was developed under the direction of the U.S. Army Corps of Engineers and involves support from the Department of Defense, the Department of Energy, and the Environmental Protection Agency. 

Aquifer Characterization
ENW uses a variety of computer programs for analysis of aquifer parameters and well-field performance. These include AQTESOLV (a program that performs curve-fitting analysis to a wide range of aquifer test solutions and variable head test solutions), THCVFIT (which fits drawdown data to the Theis equation), THEISFIT (a statistical best-fit program for fitting drawdown data to the Theis equation), VARQ (a variable discharge pump test analysis package), and OPTP/PTEST (uses variable discharge pump test data to determine optimum pumping discharge).

When ENW prefers to analyze aquifer characteristics outside of the constraints of prepared programs, our hydrogeologists use Microsoft Excel, a spreadsheet program with excellent graphic capabilities, which can also export data to and from other formats.

ENW is experienced with using sophisticated electronic pressure transducer systems (made by In Situ) to acquire and record high-quality data during pump test and down-hole testing procedures. 

Risk Assessment
Modeling of impacted hydrogeologic systems can assist in matters of public policy, planning, and response. ENW has used modeling to assess the risk to water well owners, public water supplies, surface waters, and industrial-agricultural users.

Remediation
ENW staff have been frequently called upon to remediate sites where groundwater has already been impacted. In attempting to remediate a groundwater contamination site, several alternative technologies may be considered. Groundwater modeling is used to test the configuration of various arrays of extraction wells to determine the most efficient capture scenario for an expanding, migrating plume. Cost-efficiency and time-efficient performance frequently are the deciding factors among the various alternatives. 

Prominent Hydrogeologic Projects

Lake Umatilla, Columbia River, OR and WA
When the US Corps of Engineers considered lowering the water level of Lake Umatilla, the body of water impounded by John Day Dam on the Columbia River, on a yearly schedule to encourage migration of threatened anadromous fish species, Mr. Woller was requested to evaluate the effects of lowering the lake level on water wells in the surrounding areas. The study included recommendations and cost estimates for mitigation of lost well production for five common well types found in the lake basin.

Indian Reservation Tribal Hatchery, Washington
When declining well production and spring flow hampered the operation of this hatchery, Mr. Woller’s well evaluation indicated that over-pumping caused plugging of the well screen and cavitation, which lowered the well's specific capacity. Mr. Woller explored options for rehabilitating the well to original condition, and also sited and designed additional wells.

City Water Station, Clark County, WA
When a city in Washington identified trichloroethylene (TCE) contamination in some of their municipal water wells, Neil Woller was the Hydrogeologist on the team selected to identify the contamination source, define the contaminant plume, evaluate hydraulic parameters of the pathways from the source area to the well field, and make recommendations for remedial actions. A thorough historical investigation was made, which included review of available well records, discussions with long-time residents, and careful following of leads. The major contaminant source was identified, and contaminant concentration contours were prepared. 

Water Resources Development Feasibility Study, Indian Reservation, WA
Neil Woller completed a feasibility study for developing water resources for a proposed fish hatchery water supply. A water well, capable of yielding 1,700 gallons per minute, was designed, sited, completed, and tested.

Landfill, Eastern Oregon
Neil Woller supervised the Siting Study and Site Characterization Investigation for a large regional landfill. The landfill is now in operation and currently accepts solid waste from a large urban city and surrounding areas. The landfill will eventually encompass one square mile in area, and has a projected lifetime of 30 years.

Proposed Railroad Tunnel, Northeast Oregon
Neil Woller was the Senior Hydrogeologist for the feasibility investigation for construction of a railroad tunnel across the crest of the Blue Mountains. The proposed tunnel, approximately 11 miles long, would have been the longest tunnel in North America. The study required a geologic and hydrogeologic evaluation of the proposed tunnel area to select from several proposed tunnel alignments. 

Golf Course, Willamette Valley, OR 
Neil Woller was the Senior Hydrogeologist for the project team that planned and constructed a golf course on a highland overlooking the Willamette River. Mr. Woller conducted a groundwater resource study to evaluate the potential for water wells to provide irrigation and domestic water for the golf course and proposed residential development. Subsequent aquifer testing in deep, domestic wells confirmed the resource study. 

Water Quality, Analysis of Potential for Impacts, Municipal water system, Willamette Valley, OR
Lynn Green coordinated and performed a large-scale field investigation to address potential impacts to a moderate size city’s drinking water source and to map the geologic and hydrogeologic features of the study area. The study incorporated the collection of numerous water-quality samples and performance of various field and laboratory analyses. He interpreted the results of the investigation and wrote the final report for the project. He formally presented his study to officials of the City and Oregon State University.

Fish Hatchery, Southern Oregon
The hatchery's main water supply was augmented by reservoir water. The hatchery had experienced high mortality rates in their incubation area due to bacteria and parasites transmitted through the reservoir water. As a result, the hatchery sought a clean new source of water for their incubation process. Mr. Woller investigated groundwater resources in the vicinity of the hatchery and completed a water supply well for the small community surrounding the hatchery.

Geothermal Resource Assessment, Oregon Cascade Range
As Geologist with the Oregon Department of Geology and Mineral Industries, Mr. Woller was an integral member of Oregon’s Geothermal Resource Assessment Team. Mr. Woller performed geologic and hydrogeologic mapping of many Known Geothermal Resource Areas.  Many of his geologic maps and hydrogeologic findings have been published in Department publications and professional journals. Mr. Woller contributed to the integrated model of volcanism and hydrogeologic systems for the mountain range.  

Community Water Association, Columbia County, OR
Mr. Woller conducted a water resource study for a small community water association for the Columbia County Community Development Agency. The association was using a spring and an inadequate well to supply 25 families. The shortage of water was causing hardships among the member families and depressing real estate values. In addition, the association’s water storage facility was leaching contaminants into the water supply. Mr. Woller identified a water resource capable of providing the necessary water production. He also recommended major modifications to the association’s water storage system because of slope stability hazards.

Golf Course, Washington County, OR
Neil Woller prepared a hydrogeologic assessment for this proposed golf course project near Hillsboro, Oregon. A special well construction was specified to produce the required quantity of potable water for the course clubhouse. The potential for degradation of ground water and surface water quality by herbicides, pesticides and fertilizers commonly used for course landscaping was assessed.  

Proposed Gas Station Facility, Clark County, WA
This site is located within a wellhead protection area delineated by another consultant.  As the proposed site usage was to dispense petroleum products, a risk analysis was required to demonstrate that the proposed site usage would not adversely impact the regional aquifer.  Mr. Green assisted with the hydrogeologic characterization and recommended numerous site controls and best management practices for the proposed facility. 

Aquifer Characterization, California
The well field is experiencing contaminant impacts and performing a complex remediation as the result of a historical operation of a coal-gasification facility. ENW utilized the data from 30 days of pump testing with numerous observation wells to characterize the two aquifers involved in this study. The results of this characterization were used to further refine remedial strategies, optimize pumping rates, and define zones of capture of extraction wells. 

Proposed Water Supply Well, Dairy Facility, Tillamook County, OR
As new land acquisition was under consideration, characterization of the aquifer was necessary to ensure that the available water resource would meet the demand of dairy operation. ENW utilized the data from a pump test to characterize the aquifer underlying the property. The results of this characterization were used to support the decision to pursue the acquisition.   

Dam Drain Network Characterization, Hood River County, OR
Due to failure of a drain system on a dam, ENW was asked to model the drain network to determine leakage volume through the dam. ENW utilized analytical models to model the complicated flow system and calculated flows expected during each phase of drain replacement. The study included recommendations for drain system design and safety procedures to be implemented while performing the remedial work. 

City Well Field, Oregon
Lynn Green worked with Portland State University in using a numerical model (Modflow) to model the aquifers of a well field and evaluate the potential for impacts to the well field from nearby environmental sites of concern. Additionally, remedial strategies were investigated using Modflow to determine if a network of capture wells could be utilized to protect the well field.