Monitoring groundwater and river interaction along the Hanford reach of the Columbia River

Abstract

Executive Summary qAs an adjunctto efficient HartfordSite characterizationand remediationof groundwater contamination,an automaticmonitor networkhas been used to measureColumbiaRiver and adjacent groundwaterlevels in several areasof the HartfordSite slice 1991. Waterlevels, temperatures,and electrical conductivity measuredby the automaticmonitor networkprovided an initial databasewith which to calibratemodels and from which to infer groundand river water interactionsfor site characterizationand remediationactivities. Measurementsof the dynamic river/aquifersystem have been simultaneousat l-hr intervals, with a quality suitable for hydrologicmodeling and for computer model calibrationand testing. This reportdescribesthe equipment,procedures, and results from measurementsdone in 1993.During 1993, ColumbiaRiver and groundwaterelevations were measuredhourlyat 50 locations in seven areas of the HanfordSite in southcentralWashington State. Watertemperaturewas measured at I0 of these locations; electrical_nductivity was measuredat five.Waterlevel accuracyis unknown, but is believed to be within +0.I ft. Factorsaffectingaccuracy are topographic surveys, instrumentcalibrations, and steel tape measurements. Measurementprecision appearsto be within 4-0.02 ft for wells and 4-0.2 ft for river stage. Repeat,xlsteel tape measurements vary within +0.01 ft. Survey errorsvary with distance between sites, but most @pearto be less than 4.0.07 ft. Visual inspectionand graphic review of data confirmedits continuity. Comparisonsbetween simultaneoussteel tape and dataloggerreadingswere used as periodic data qualitychecks. River elevations varied up to 15 ft during the year and up to 9 ft duringa single day. The 300 Areariver elevationvaried about60% as much as the other stations becauseof the influenceof the McNary Dam forebay. Ice Harbor Dam tailwateralso influencedthe fluctuationof the river in the 300 Area. Groundwaterelevations varied up to about3 ft per day in a few wells nearest the riverand up to about 6 ft over the season in some wells.Electricalconductivityof water in wells was influencedby river intrusionto a small degree. Riverbank seep conductivity varied between river and well values. Each of these factors is important in more efficient site characterizationand remediafion. ee. 111

Three-Dimensional Groundwater Models of the 300 Area at the Hanford Site, Washington State

“…The current network consists of 13 wells and was established in 2004 ). An earlier network was established in the early 1990s and operated until the mid-1990s (Campbell 1994, Campbell andNewcomer 1992). These networks and data analysis are discussed in Sections 2.3.1 and 2.3.2.…”

“…Pressure transducer data were checked periodically with manual water-level measurements for these wells. These data, which are maintained by Fluor Hanford, Inc. (Richland, Washington), are described in Campbell (1994) and Campbell and Newcomer (1992).…”

“…Hydraulic properties are estimated by comparing simulation results over a range of specified values with extensive hourly water-level measurements collected from a network of wells around the 300 Area from December 1991 through March 1993 (Campbell 1994, Campbell andNewcomer 1992). Wells with water levels in the uppermost portion of the aquifer during this time period are shown in Figure 2.27.…”

“…This facility received discharges from the 300 Area process sewer. Estimated volumes of water discharged to the 316-5 Facility are tabulated in Table 3 -2 of DOE-RL (1997, 1993, and 1994, the estimated volumes of water discharged to the 316-5 Facility were 1290, 568, 416, and ~378 million L (3.4E+8, 1.5E+8, 1.1E+8, and ~1.0E+8 gal), respectively (DOE-RL 1997). The 316-5 Facility is comprised of two parallel trenches located north of the 300 Area boundary (see Discharge to the trenches ended in 1994 when the effluent from the process sewer was routed to the 300 Area Treated Effluent Disposal Facility.…”

“…These models used a common three-dimensional hydrostratigraphic framework developed from extensive site characterization studies (discussed below), and encompass the upper portion of the unconfined aquifer and the lower portion of the vadose zone. The first model has a larger domain (see Figure 1.2) and was based on a water-level monitoring network operated during the early to mid-1990s (Campbell 1994, Campbell andNewcomer 1992). The second, smaller-scale model focused on the northern portion of the 300 Area (see Figure 1.2) and was based on the current water-level monitoring network established in 2004 by the Remediation and Closure Science (RACS) Project.…”