Groundwater and Surface Water Modeling
Groundwater Flow / Dewatering
Oakland A’s Proposed New Ballpark, Oakland, California:
LWS is currently working on a steady-state and a transient MODLFOW numerical groundwater model of the proposed site of the new Oakland A’s ballpark in downtown Oakland. The stadium is proposed to be located adjacent to the Inner Harbor, which connects to the San Francisco Bay. As such, there are potential groundwater management issues, including groundwater inflow into the ballpark area, as well as increased flows over time due to sea level rise. It is proposed that a cutoff wall be installed around the ballpark area to minimize groundwater management; however, there are multiple options for the cutoff wall design where groundwater management versus cost issues have to be weighed. LWS is finalizing a groundwater model to evaluate providing permanent dewatering inside the cutoff wall to varying depths that will be used to make decisions on the elevations of specific aspects of the ballpark and to design the interior drain that will provide adequate dewatering.
Reclaimed Open Pit Mine Water Management Plan, Southern Colorado:
A retired open pit mine in southern Colorado has been reclaimed with waste rock. However, as the pit filled with native groundwater, there ultimately were some discharges from the reclaimed pit that didn’t meet stream water quality standards. Therefore, a series of wells were installed by LWS and a pump and treat system was installed to manage groundwater that would otherwise discharge. A remediation plan has been in place for a number of years to manage water levels and treat water that would otherwise discharge. The client would like to evaluate alternatives to the current groundwater management plan, and LWS has been working on a transient MODFLOW groundwater model on the reclaimed pit to assess alternative actions. This work has included a multi-model analysis (MMA), which evaluate multiple conceptual models and assess the variability of the MMA model results to determine the sensitivity of parameters in the model that are not completely defined.
Renewable Water Resources Water Supply Development Project, San Luis Valley, Colorado:
Renewable Water Resources is evaluating a water supply delivery project to develop up to 25 deep alluvial wells (up to 2,000 feet deep) in the San Luis Valley and transport that water to Colorado’s Front Range for municipal water supplies. LWS has used the existing Rio Grande Decision Support Systems (RGDSS) numerical MODFLOW ground water flow model to evaluate the ability to develop a 22,000 ac-ft/yr water supply project well field through deep groundwater wells. This assessment evaluated the flow rates and spacing of wells to optimize the well field yield. LWS also used the RGDSS model to assess potential injury to other water rights within the basin. Since the wells as part of this project are new water rights, development of new water can’t injure senior vested water rights. Because of this requirement the project will have to adjudicate an augmentation plan to offset injurious depletions to other water rights, therefore, multiple MODFLOW model analyses were completed to assess injury and evaluate the most efficient means to develop an augmentation water supply that will offset that injury.
Energy Fuels Sheep Mountain Project, South-Central Wyoming:
Energy Fuels is proposing an open pit uranium mine, with the possibility of also re-opening historic underground mine workings. As part of the permitting process, the proposed open pit uranium mine in Fremont County, Wyoming had to demonstrate that it will not impact flows on Crooks Creek, a tributary to the Sweetwater River, which is then a tributary to the North Platte River. The proposed open pit mine plan includes eight separate pit areas that will need to be dewatered for the mining operation. These pits will be staged so that, as one pit is finished mining, it will be backfilled with overburden from the next pit to be mined. LWS developed a MODFLOW model of the pit sequencing to assess how each individual pit could be dewatered. As part of this analysis, LWS also assessed the resultant changes in groundwater flow patterns due to dewatering and subsequent mining of the open pit. The results of the LWS modeling were used by Energy Fuels to obtain a mine permit from the Wyoming Division of Environmental Quality.
Timnath Landing Dewatering, Northern Colorado:
A property in Timnath, Colorado is proposed for residential and commercial development and the property is located above an ancient paleochannel of Box Elder Creek. Because of this, the site experiences high groundwater levels from a very permeable alluvial channel running beneath the site. LWS developed a steady-state and a transient numerical ground water flow model using MODFLOW to evaluate the most efficient means to dewater the alluvial aquifer underlying the proposed residential and commercial development areas. The proposed dewater methodology was the construction of three unlined ponds that will drain adjacent alluvial aquifer water by gravity, with the ponds being maintained at constant elevations that will facilitate permanent dewatering. The results of the LWS MODFLOW model have been used by the civil engineering firm that is preparing the development plan, as it demonstrates the means to dewater the site to allow foundation and basement construction. The LWS model was also used to support a Water Court application to adjudicate an augmentation plan so that the capture of water in the dewatering ponds will not injuriously affect senior vested water rights.
Front Range Resources ASR Project, Eastern Colorado:
Front Range Resources has a large groundwater rights portfolio in the Lost Creek Basin on the eastern plains of Colorado. Because of limited water supply availability on the eastern plains, Front Range Resources wanted to evaluate the use of aquifer storage and recovery (ASR) to retime source water from periods of excess supply to times of demand. LWS constructed both a steady-state and a transient numerical ground water model of the Lost Creek Basin alluvial aquifer using MODFLOW. The proposed ASR project is to recharge water into the Lost Creek alluvial aquifer using three separate rapid infiltration basins (RIBs) and the recharged water will subsequently be recovered through a series of 33 alluvial aquifer wells located downgradient of the RIBs. Parametric studies were conducted using the results from the MODFLOW model to demonstrate not only could the water be efficiently recovered by the downgradient wells but also will prevent injury to other existing wells in the basin.
Fort Knox Gold Project, Central Alaska:
As part of the development of the gold project, a Tailing Storage Facility (TSF) had to be constructed on Fish Creek, a tributary to the Tanana River north of Fairbanks. The proposed TSF was not lined and, therefore, there was the potential for outflows either beneath the dam through fractured rock or around the abutments as previously frozen ground, i.e., permafrost, dissipated due to the energy in the tailings facility. LWS personnel modeled the groundwater flow downstream of the TSF and then designed a series of monitoring/production wells that could be used to (a) monitor alluvial groundwater quality to detect releases from the TSF and (b) if any releases were detected, pump the wells to create a hydraulic stall, delivering the pumped water back into the TSF. The results of the modeling and well design were provided to the regulatory agencies and the TSF was permitted.
Cherry Creek Alluvial Modeling Project, Denver Metropolitan Area:
There are a number of water supply entities in the Upper Cherry Creek Basin in the Denver metropolitan area (upstream of Cherry Creek Reservoir) that compete for relatively small renewable water supplies on Cherry Creek. These entities decided to evaluate regional cooperation possibilities through the use of a numerical surface water/groundwater hydraulic interaction flow model, as well as a water rights assessment tool. LWS developed the numerical surface water/groundwater model using MODFLOW. The model simulates the alluvial pumping points for each water supply entity, as well as the surface diversion for Rueter-Hess Reservoir, and discharge points associated with water reclamation facilities. The model has been used to evaluate multiple water use, and water sharing, scenarios to evaluate optimizing the beneficial use of limited Cherry Creek water supplies.
Hydrologic Flow Modeling To Support The Design Of A Water Supply Reservoir To Serve The Fort Knox Mine Near Fairbanks, Alaska :
A water supply reservoir was required to meet the water demands for a proposed mill associated with a large gold mining project. The size of the reservoir to meet the mill demands had to be determined through hydrologic flow modeling of Fish Creek, as well as Last Chance and Solo Creeks. The analysis of the availability of surface water flows was complicated by permafrost conditions and extensive ice issues during the wintertime. The result of the analyses was that either reservoir was designed that was sufficient to meet all of the mill demands even under the harsh wintertime conditions at the site.