Geothermal Water Resource Services
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Site Characterization - Groundwater Resource Information Sources
Water/Ground Source Selection and Modeling The type of heat/cooling source chosen depends on the available land areas and the soil and bedrock types at the installation site. These factors will help determine the most economical choice for installation of the heat/cooling source ground loop. The demand of the geothermal heat pump will also dictate to some degree the type of system selected. Heat/cooling source possibilities include:
Thermal plume modeling is performed to predict the long term efficacy of the various heat/cooling source design options. Through an iterative modeling process, the optimum heat/cooling source can be selected and vital design parameters determined early in the physical plant design process. The thermal model is often utilized several times during the design process to evaluate the impact of plant design modifications allowing for flexibility in building design without overstepping the heat/cooling sources capabilities. Groundwater, Aquifers, Wells and Well Flow Testing Utilizing the heating and cooling demand for a project, the best source water for the geothermal system will be determined based on an understanding of the local geology and hydrogeology, When an underground source is to be utilized, there are several source "development" tools available to help achieve a higher probability for success. This includes the use of fracture trace analysis, coupled with very low frequency (VLF) surveys and magnetometer readings. A review of well completion records for a region can also be conducted to determme aquifer (bedrock) geology and yield potential. If necessary, a pumping test can be performed on both surface and groundwater sources for the determmation of a long-term safe yield for the water source, and to determine what effects (changes in water chemistry, temperature, level, etc.) the pumping is predicted to have. These data are incorporated into the thermal model to "fine tune" the predicted capability of the heat/cooling source capabilities. Groundwater Chemistry and Analysis The determination of source water geochemistry is cntlcal to the optimal performance of a geothermal system. While the quality of the source water does not need to meet the levels for potable consumption, there are several water quality parameters that should be evaluated with regard to possible component performance and compatibility issues. This can include pH, temperature (for heat or cooling exchange), iron, manganese, corrosively, total suspended and total dissolved solids, hardness, and alkalinity. Additional analyses for aquatic micro·organisms and fungi/algae are also recommended when using a surface water resource. Our knowledge of the source geology and hydrogeology will determine the appropriate water chemistry evaluations to perform. Injection Wells, Permitting and Monitoring When an open loop system is selected, water will be withdrawn from a groundwater source and re-injected back into the ground. The State of Vermont, through the Agency of Natural Resources (ANR), regulates the sub-surface discharge of all non-sanitary waste (including return water and "bleed" water from open loop geothermal systems) by requiring that an Underground Injection Control (UIC) permit be obtained. The purpose of this rule is to:
Each open loop geothermal system will require for a permit to discharge waste waters into an injection well. H&N is experienced in completing the supporting documentation required. This includes site-specific geologic and hydrogeologic informatlon regarding the water source, the discharge (injectlon) method (basin or well) and anticipated thermal plume generation. Dependmg on the volume of discharge, onsite characteristics, and potential for influence on neighboring water supply resources, a monitoring plan, which is a component of the UIC application, will likely be required. The monitoring plan will often require installation of groundwater monltormg wells, and observation of other site-specific response characteristics once the system is up and running. Through utilization of automated data collection devices and a logical, system specific monitoring plan we strive to minimize the impact of monitoring on the clients operation and maintenance of the facility. |
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For the past 28+ years Heindel & Noyes, Inc. (H&N) has been Involved In hundreds of site investigations that include geologic and hydrogeologic analysis for small scale and large-scale water supply projects. With all of the existing reports at our disposal along with an extensive Geographic Information System (GIS) that includes such data as private drilled wells, public community water supplies, bedrock geology, aerial photography, parcels, and a number of other mapping datasets, H&N is prepared to handle the site complexities that often arise in the layout and selection of a groundwater resource.