PNNL

Abstract

This report documents both the field characterization activities and the numerical modeling effort at the BSF/CSF site to determine the viability of an open-loop ground source heat pump (GSHP). The primary purpose of the integrated field and modeling study was to determine far-field impacts related to a non-consumptive use water right for the well field containing four extraction and four injection wells. In the field, boreholes were logged and used to develop the geologic conceptual model. Hydraulic testing was performed to identify hydraulic properties and determine sustainable pumping rates. Estimates of the Ringold hydraulic conductivity (60-150 m/d) at the BSF/CSF site were consistent with the local and regional hydrogeology as well as estimates previously published by other investigators. Sustainable pumping rates at the extraction wells were variable (100 – 700 gpm), and confirmed field observations of aquifer heterogeneity. Field data were used to develop a numerical model of the site. Simulations assessed the potential of the well field to impact nearby contaminant plumes, neighboring water rights, and the thermal regime of nearby surface water bodies. Using steady-state flow scenarios in conjunction with particle tracking, a radius of influence of 400–600 m was identified around the well field. This distance was considerably shorter than the distance to the closest contaminant plume (~1.2 km northwest to the DOE Horn Rapids Landfill) and the nearest water right holder (~1.2 km southeast to the City of Richland Well Field). Results demonstrated that current trajectories for nearby contaminant plumes will not be impacted by the operation of the GSHP well field. The objective of the energy transport analysis was to identify potential thermal impacts to the Columbia River under likely operational scenarios for the BSF/CSF well field. Estimated pumping rates and injection temperatures were used to simulate heat transport for a range of hydraulic conductivity estimates for the Ringold Formation. Two different operational scenarios were simulated using conservative assumptions, such as the absence of river water intrusion in the near shore groundwater. When seasonal injection of warm and cool water occurred, temperature impacts were insignificant at the Columbia River (