* Dr. Innis was present only for the portion of
the meeting pertaining to UTSA.
** Minutes prepared by Gary Cobb, Parsons.
These meeting minutes are organized in the order discussed.
Preliminary Results of Soil Gas
Treatability Study at AOC-65
The meeting was opened with a discussion of the current status of the soil gas
treatability study at AOC-65. In November 2002, Parsons initiated the startup
and testing of the Building 90 Subslab Soil Vapor Extraction (SVE) system and
the AOC-65 SVE system and preliminary results were discussed. Participants in
this portion of the meeting included CSSA, USACE, Portage Environmental, and
Parsons.
On December 3, 2002, Parsons performed the startup and testing of the Building
90 Subslab SVE and AOC-65 SVE systems. Prior to the startup of the system
blowers, soil gas concentrations at SVE monitoring points for the two SVE
systems were measured using a photoionization detector (PID) meter and an
oxygen/carbon dioxide meter. The soil gas concentrations were measured to
determine subsurface conditions prior to initiating the extraction tests. Soil
gas concentrations, pressure readings and airflow rates were measured from the
systems following initiation of the startup tests.
For the AOC-65 SVE system, soil gas was extracted from vapor extraction well (VEW)-19
for the startup test and pressure responses were measured in vapor monitor
points (VMPs) 1 - 5. The AOC-65 SVE startup test was terminated prematurely
after only four hours of operation due to water drawing up to block the entire
screened interval in the extraction well which caused the blower to overheat and
automatically shut down. During the abbreviated startup test, the pressure
readings in shallow zone and deep zones of VMP-4A (4-10’), VMP-4B (41’), and
VMP-3 (38-48’), the closest monitoring points to extraction well VEW-19 (with
effective screened interval of 10-15’ below ground surface [bgs]), did not
exhibit significant responses suggesting little interconnection between the
extraction zone and these monitoring zones. The pressure readings from these
monitoring points exhibited an almost instantaneous response indicating a direct
vertical connection between the extraction intervals and these monitoring
zones.
Groundwater samples were collected from AOC-65 SVE extraction wells VEW-15,
VEW-19, and VEW-16, and submitted to DHL for volatile organic compound (VOC)
analysis (SW 8260B short list [acetone, methyl ethyl ketone,
cis-1,2-dichloroethene, trans-1,2-dichloroethene, tetrachloroethene,
trichloroethene, toluene, and isopropyl alcohol (tic)]).
Results of the groundwater samples identified the presence of tetrachloroethene
(PCE) at concentrations ranging from 35.5 micrograms per liter (μg/L) in VEW-15
to 546 μg/L in VEW-19. Trichloroethene (TCE) was present at concentrations
ranging from 15.5 μg/L in VEW-15 to 73.3 μg/L in VEW-19. Laboratory results of
the soil gas samples collected during the startup tests have not been received.
PCE was the only contaminant detected in the sample collected from AOC-65 VEW-16
(at 37.0 μg/L). Parsons anticipates continuing the initial system check and
testing of this system in January 2003.
Startup testing of the Building 90 SVE system consisted of extracting soil gas
from each of the 12 VEWs and monitoring soil gas concentrations and air flow.
During the startup test, the SVE blower operated for seven days and soil gas and
airflow readings were measured periodically on December 5, 6, 9, and 11.
Results of the soil gas screening indicates that the concentrations increased
with time during the initial phases (first few hours) of the test then declined
steadily to concentrations significantly lower than pretest levels. Parsons
will monitor soil gas concentrations in the VEWs/VMPs to assess the rate of
accumulation of vapors in the subslab material.
CSSA requested Parsons to bail the wells that have water in them. The bailed
water will be treated at the GAC unit. The wells will be monitored to determine
recharge. If the wells do not fill up with water again, then the SVE system can
continue using these wells. If the wells recharge, research will need to be
conducted to ascertain how and why the water enters the wells so readily. Also,
those wells impacted may have to be removed from the extraction system. The
accumulation of water in the AOC-65 VEWs raises a concern by CSSA that there
possibly is a water leak from the water lines feeding Building 90. CSSA is
aware that there are leaks from the water distribution system and a leak at
Building 90 could allow water to migrate through the impacted shallow material
and contribute to the spread of groundwater contamination.
Additionally, the automated collection of water levels in the AOC-65 piezometers
using the weather station data logger experienced some difficulties during the
initial month of data collection. There appears to be problems with adjusting
the water levels measured in some piezometers to a mean sea level datum. Also,
the water level data is being stored with previous days date rather than the
date the measurements are collected. Both these items appear to be problems
with the program that controls the collection and storage of the data by the
data logger. Parsons will contact the vendor, Campbell Scientific, to get
technical assistance with resolving the programming problems.
Review of DQOs for AOC-65 Treatability Study
CSSA has prepared draft DQOs to address shallow groundwater sampling activities
conducted as part of the overall groundwater investigation at AOC-65. During
the startup testing of the SVE systems at AOC-65, groundwater was found to
accumulate in the shallow extraction wells west of Building 90. CSSA and
Parsons decided to sample this shallow groundwater to assess the distribution
and migration on contaminants through the shallow subsurface materials. A draft
document prepared by CSSA presents suggested DQOs for the sampling of shallow
groundwater from the SVE extraction wells. Parsons will review the draft DQOs
and incorporate this information into the AOC-65 DQO document for consideration
and discussion at a future TIM. TIM #6 will be scheduled for January 2003 so
that the shallow groundwater DQOs can be resolved. This will ensure that the
appropriate data is obtained for CSSA use under TO 0058.
Discuss UTSA Research and Tracer Test Proposals
A discussion of the latest proposals from UTSA for conducting research and soil
gas tracer tests was conducted with Dr. Ennis of UTSA. UTSA has proposed to
conduct soil gas tracer tests in the AOC-65 area to assess interconnectivity of
fractures/faults in the area and to determine the optimum partial saturation
level for the extracting PCE/TCE vapor from the unsaturated material around
AOC-65. Additionally, UTSA has proposed to conduct permeability and contaminant
absorption studies on select rock cores collected during drilling activities
around AOC-65/Building 90.
CSSA and Parsons agreed that the decision to perform the tracer tests is
premature given the limited information obtained from the SVE systems to date.
Additional data collection and evaluation is warranted to determine if the
benefits offered by the tracer tests justify the proposed costs. Dr. Bill
Blanford at Louisiana State University (formerly of UTSA), who authored the UTSA
proposal, was contacted in a conference call during the meeting to determine if
the proposed costs of $30,000 for the tracer tests can be reduced. Dr. Blanford
indicated that reductions in the tracer test costs are not possible and that he
thought the costs were justified by the information that will be gained
regarding the optimum saturation levels for effective SVE operations. Given the
costs and the premature nature of the tracer tests, CSSA decided not to proceed
with the current UTSA proposals.
Discussions were continued with Dr. Ennis regarding possible alternate research
activities that UTSA may be able to provide. CSSA indicated that it would like
to assist UTSA with potential research studies associated with planned
activities at AOC-65 and SWMU B-3, but justification of expenditures for UTSA's
research may be difficult. Dr. Ennis suggested that there may be research
activities that can be conducted with little or no costs to CSSA. Dr. Ennis
will develop and submit a proposal for additional tests to CSSA. Specifically,
UTSA may request CSSA to participate in the purchase of some test equipment that
could be used to perform the testing.
Evaluation of Borehole Flowmeter Options
Parsons has conducted a preliminary
evaluation of borehole flowmeters that may be used to monitor groundwater flow
rates and directions at specific subsurface locations near AOC-65. Parsons
obtained and reviewed several technical documents related to the evaluation of
various types of borehole flowmeters. From the technical documents, the
heat-pulse flowmeters are frequently the preferred equipment for measuring
groundwater flow within a borehole. However, based on information presented in
these technical documents, concerns related to the accuracy and repeatability of
borehole flow measurements were identified. Parsons will contact individuals
with direct recent experience using borehole flowmeters, specifically the
heat-pulse flowmeters, to determine if borehole flow measurements should be
conducted and gain understanding into how to effectively perform the
measurements.
Action items
Agenda for Technical Interchange/Progress Meeting #5
CSSA Treatability Study and Removal Action
Area of Concern 65 (Building 90)
Time: Thursday, December 19, 2002; 09:00 am
to 1:00 pm
Place: Camp Stanley Storage Activity, Boerne, Texas,
Environmental Office
OBJECTIVES:
1. Discuss preliminary results from soil gas treatability study.
2. Discuss and review UTSA research and tracer test proposals.
3. Review DQOs for Treatability Study relative to Future
Investigation and Treatability activities at AOC-65 and as part of the Overall
Groundwater Investigation at CSSA.
4. Discuss borehole flowmeter assessment.
Proposed Order of
Discussion
