Results of Detailed Hydrologic Characterization Tests - Fiscal Year 1999

TLDR: In this paper, the results of detailed hydrologic characterization tests conducted within newly constructed Hanford Site wells during FY 1999 were provided, which included: groundwater flow characterization, barometric response evaluation, slug tests, single-well tracer tests, constant-rate pumping tests, and in-well vertical flow tests.

Abstract: This report provides the results of detailed hydrologic characterization tests conducted within newly constructed Hanford Site wells during FY 1999. Detailed characterization tests performed during FY 1999 included: groundwater flow characterization, barometric response evaluation, slug tests, single-well tracer tests, constant-rate pumping tests, and in-well vertical flow tests. Hydraulic property estimates obtained from the detailed hydrologic tests include: transmissivity, hydraulic conductivity, specific yield, effective porosity, in-well lateral flow velocity, aquifer flow velocity, vertical distribution of hydraulic conductivity (within the well-screen section) and in-well vertical flow velocity. In addition, local groundwater flow characteristics (i.e., hydraulic gradient and flow direction) were determined for four sites where detailed well testing was performed.

Figures

Table 9.2. Tracer-Dilution Test Summary

Figure 7.9. Composite Type-Curve and Derivative Plot Analysis for Pumping Well 299-W14-13 and Observation Well 299-W14-12

Table 7.1. Constant-Rate Pumping Test Summary

Figure A.2. Multiple-Regression, Model-Predicted, and Barometric Corrected Water-Level Responses for Well 299-W10-18 and 299-W10-26

Figure 8.6. Calculated Average, In-Well, Downward, Vertical Flow Velocity Within Well 299-W14-13, Using Center-of-Mass Method (btoc = below top of casing)

Figure 4.3. Selected Slug-Test Analysis Plots for Well 299-W10-24 (Bouwer and Rice method [top] and type-curve method [bottom])

Full text

PNNL-13378
Results of Detailed Hydrologic
Characterization Tests –
Fiscal Year 1999
F. A. Spane, Jr.
P. D. Thorne
D. R. Newcomer
January 2001
Prepared for the U.S. Department of Energy
under Contract DE-AC06-76RL01830

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(8/00)

PNNL-13378
Results of Detailed Hydrologic Characterization
Tests – Fiscal Year 1999
F. A. Spane, Jr.
P. D. Thorne
D. R. Newcomer
January 2001
Prepared for
the U.S. Department of Energy
under Contract DE-AC06-76RL01830
Pacific Northwest National Laboratory
Richland, Washington 99352

iii
Abstract
This report provides the results of detailed hydrologic characterization tests conducted within newly
constructed Hanford Site wells during fiscal year 1999. Detailed characterization tests performed
included groundwater-flow characterization; barometric response evaluation; slug tests; single-well tracer
tests; constant-rate pumping tests; and in-well, vertical flow tests. Hydraulic property estimates obtained
from the detailed hydrologic tests include transmissivity; hydraulic conductivity; specific yield; effective
porosity; in-well, lateral flow velocity; aquifer-flow velocity; vertical distribution of hydraulic conduc-
tivity (within the well-screen section); and in-well, vertical flow velocity. In addition, local groundwater-
flow characteristics (i.e., hydraulic gradient and flow direction) were determined for four sites where
detailed well testing was performed.

v
Summary
The Pacific Northwest National Laboratory,
(a)
as part of the Hanford Groundwater Monitoring
Project, examines the potential for offsite migration of contamination within underlying aquifer systems.
Hydraulic property estimates obtained from the analysis of hydrologic tests are important for evaluating
aquifer-flow characteristics (i.e., groundwater-flow velocity) and transport travel time. This report
presents test results obtained from the detailed hydrologic characterization program of the unconfined
aquifer system conducted for the Hanford Groundwater Monitoring Project during fiscal year (FY) 1999.
Hydrologic tests conducted as part of the detailed program include the following:
• slug testing (10 wells tested)
• tracer-dilution tests (4 wells tested)
• tracer-pumpback tests (4 wells tested)
• constant-rate pumping tests (4 wells tested)
• vertical flow, in-well tracer tests (2 wells tested).
Hydraulic property estimates obtained from the detailed hydrologic tests include hydraulic conduc-
tivity; transmissivity; specific yield; effective porosity; in-well, lateral, groundwater-flow velocity;
aquifer-flow velocity; vertical distribution of hydraulic conductivity; and in-well, vertical flow velocity.
In addition, local groundwater-flow characteristics (i.e., hydraulic gradient, flow direction) were deter-
mined for four sites that had detailed well testing performed. Pertinent results from the FY 1999 detailed
characterization program are summarized below.
Slug-test results provided hydraulic conductivity estimates for the Ringold Formation (gravel Unit E)
that range between 0.88 and 9.5 m/d for the nine 200-West Area wells and 24.2 m/d for the Hanford
formation at the one 200-East Area well tested. The results fall within the previously reported slug-test
values for the Ringold and Hanford formations within the 200-West and 200-East Areas.
The hydraulic conductivity estimates derived from slug tests correspond closely with values obtained
from constant-rate pumping tests and fall within the error range commonly reported for slug tests in
aquifer characterization studies (i.e., within a factor of ∼2 or less). The close correspondence is
attributed, in part, to improved analysis methods for slug tests. The close correspondence between slug-
test and pumping-test hydraulic conductivity estimates also indicates that the tested formation can be
represented as a homogeneous unit at the slug-test or larger scale.
Constant-rate pumping-test results for transmissivity ranged between 66 and 345 m
2
/d (average
157 m
2
/d). These values fall within to slightly below recently calculated values for the central 200-West
Area. The recent estimates were based on the analysis of the induced areal composite pumping/injection
effects of the 200-ZP-1 pump-and-treat system, which produced large-scale estimates that range between
230 and 430 m
2
/d (average 325 m
2
/d).
(a) Pacific Northwest National Laboratory is operated for the U.S. Department of Energy by Battelle.

Frequently asked questions

Q1. What contributions have the authors mentioned in the paper "Results of detailed hydrologic characterization tests – fiscal year 1999" ?

In-Well, Vertical Flow Tests and In-Well Tracer-Dilution Tests this paper 3.5 3.4 3.3 Diagnostic Analysis and Derivative Plots 3.2 3.1 2.3. 

Q2. How was the tracer introduced into the well?

The tracer was introduced into the well using a 0.025-m polypropylene tube that was open at a depth setting of 78.5 m below top of casing. 

Q3. What was the main method used to remove barometric pressure effects from the measured water levels?

The multiple-regression deconvolution technique (Rasmussen and Crawford 1997; Spane 1999) was used to remove barometric pressure effects from the measured water levels. 

Q4. What are the key design elements of a tracer-dilution test?

Essential design elements of a tracer-dilution test include establishing a known, constant tracer concentration within the test section by mixing or circulating the tracer solution in the wellbore/test interval and monitoring the decline of tracer concentration with time within the test interval. 

Q5. Why are the estimated values from the tracer pumpback test highly questionable?

Because of the vertical flow conditions that were observed during the tracer-dilution test, the estimated values from the tracer-pumpback test are highly questionable also. 

Q6. Why were drawdown data not selected for analysis?

Drawdown data were not selected for analysis because of the detrimental effects caused by small variations in discharge rate (not shown) during the test. 

Q7. Why was the water-level change monitored during the tracer pumpback test?

To determine the significance of barometric effects, water-level changes were monitored during a baseline period before or after each constant-rate discharge test and compared to the corresponding barometric pressure changes. 

Q8. What was the analysis of the drawdown and recovery phases of the constant-rate discharge?

Analysis of the drawdown and recovery phases of constant-rate discharge were then performed by type-curve fitting of log-log plots and, if appropriate, by straight-line analysis of semilogarithmic data plots of water-level change versus time. 

Q9. Why is the tracer pumpback more susceptible to wellbore effects?

Because of the relatively small area represented by the well (i.e., in comparison to the aquifer) and volumes of tracer involved, the results obtained from these tracer tests may be more susceptible to wellbore effects (e.g., ∝ and possible downgradient dead zone). 

Q10. How many times was the tube raised to allow for the insertion of the tracer?

The tube was then slowly lowered and raised eight times within the water column over a 15-min period to mix the tracer within the well-screen section. 

Q11. How was the flow rate determined during the initial minutes of pumping?

During the initial minutes of pumping (e.g., first 5 min), “instantaneous” flow rates were determined by measuring the time required for 19 L of flow to register on the flow-meter dials. 

Q12. How was the concentration within the borehole after the insertion of the sensors?

The concentration within the borehole following emplacement and equilibration of the sensors (i.e., after 70 min following initial mixing) was ~133 mg/L, ranging between 98 and 170 mg/L for the various sensordepth settings. 

Q13. What is the value of ne and va?

Based on these input parameters and tracer-pumpback results, ne and va are estimated to be 0.009 and 0.191 m/d, respectively (Figure 6.3). 

Q14. What are the estimated values for ne and va?

Based on these input parameters and tracer-pumpback results, ne and va are estimated to be 0.010 and 0.124 m/d, respectively (Figure 6.2).