Field Sampling Plan for Winston Thomas Monitoring Wells
(Bloomington QAPjP, Volume XXVII)
VIACOM
June 25, 2001
Monitoring Wells Map
Summary of Conditions W-T Monitoring wells
Initial Well Purging
Sample well purging log
Attached is the revised Field Sampling Plan for Winston Thomas Wells. (NOTE:
EPA Ground Water Issue for "Low Flow (Minimal Drawdown) Ground Water Sampling
Procedures" is not being resent.) It incorporates revisions as discussed on the
conference call of May 24, 2001, and the results of an initial field inspection
conducted on June 14 and 20, 2001.
If there are no further comments, please send a letter approving the plan. Your
response is requested by no later than July 2, 2001.
Viacom is prepared to schedule the work as soon as we receive approval from all the
parties. We will notify all concerned parties at least two business days before
beginning the purging, and again in two weeks before the start of the well sampling.
Sincerely,
Dorothy M. Alke
Director, Bloomington Project
A. Background
The Winston Thomas Site had 11 Groundwater monitoring wells installed in 1987. The
specific details and prior sampling history for these wells is reviewed in Reference 1. None
of these wells have been sampled since 1988. In the interim, the site has been remediated.
During remediation, one of the wells, MW-2, was abandoned because it was in the way of
construction. In discussions among the parties of what to include in the long term
monitoring plan for the site, a decision has to be made on whether to include the existing
monitoring wells. Viacom has proposed to do a round of sampling of the remaining
monitoring wells so the resulting data can be used in arriving at a decision.
Because the wells have not been sampled for so long, special care will be taken to ensure
that the samples are representative of current local aquifer conditions rather than an
amalgamation of pre-remedial conditions and well sampling artifacts. A brief review of each
well, including the potential water producing zone, is included in the attached summary of
Winston Thomas Well Hydrology.
B. Pre-Sampling Procedures
All wells have been located and inspected. Access and workspace has been cleared
around each well. Water levels and depth-to-bottom measurements have been taken.
Table 1 summarizes the conditions for each well. Information from the Onsite Groundwater
Monitoring Plan Winston-Thomas Facility Bloomington Indiana issued May 1989 to all
consent decree parties was referenced. The first column lists the well number. The second
column lists the elevation of the top of outer protective casing based on the previous
reference datum of 100 feet being equivalent to elevation 677.89 feet approximate mean
sea level (amsl). The third column similarly corrects the ground surface elevation at the well
to amsl. The fourth column list the depth of protective surface casing below ground surface,
which for the open-hole bedrock wells would be the minimum sampling depth. The fifth
column lists the reported well construction depth from below ground surface, and the sixth
lists the reported well construction depth from the top of the protective outer casing. The
seventh column lists the recently measured depth to bottom (DTB) from the top of outer
protective casing. The eighth column is derived from the subtraction of the measured DTB
from the reported DTB and is presumed to be the accumulated sediment in the bottom of
the well. For wells MW-51, MW-5d, MW-6, MW-7, and MW-8 the measured DTB is greater
than the reported DTB, probably indicating the previous information was incorrectly
measured or reported. The ninth column is the depth to water from top of outer casing and
the tenth column is the elevation of that water surface in amsl. The eleventh column is the
screen interval depth as measured from the top of outer casing for those wells that are
screened. The twelfth column is the proposed location of the sample intake. This location is
based either on the information in Attachment 1, or in the case of the screened wells, is the
middle of the screened interval. The thirteenth column lists the distance from the proposed
sample intake location to the measured bottom or top of accumulated sediment.
For the open-hole wells MW-1, MW-4, MW-6, MW-7, and MW-8 the distance from sample
intake to any sediment is great enough that no sediment removal is necessary, so none is
proposed. The open-hole wells will be purged by pumping 5 well volumes using a 4"
submersible pump set 5' above the bottom of the well. A sample for turbidity will be taken at
each removal of a well volume. The purge water will be containerized and disposed of at
the Neal's Landfill Spring Treatment Plant. The submersible pump and tubing will be
decontaminated prior to each use. The screened wells will be purged by pumping 5 well
volumes using a shallow well pump with polyethylene tubing and a foot valve. The wells will
be pumped through the foot valve set on the bottom of the well so that most of the
accumulated sediment will be removed. A sample for turbidity will be taken at each removal
of a well volume. The purge water will be containerized and disposed at the Neal's Landfill
Spring Treatment Plant. The shallow well pump will be decontaminated prior to each use
and the tubing will be changed.
After purging, the dedicated sample device will be installed at the depth specified in Table 1.
The wells will be sampled with a peristaltic pump. The dedicated sampling device for each
well will be a set of Teflon tubing. The end of the tubing will be placed at the depth as
specified in Table 1. Well MW--6 had a depth to water of 21.73 feet below top of casing, so a
Whale 1.75" battery-powered submersible pump with Teflon-lined tubing will be set at the
depth specified in Table 1. A minimum of 2 weeks will be allowed for the wells to settle back
down after purging.
C. Sampling Procedures
Sample the wells using the low purge methods (see attached general procedure) with either
the peristaltic pump and dedicated tubing or the dedicated submersible pump.
Pump at a low rate, such as .2 liters per minute and purge the well into a carboy/drum.
Check the water level of the well every 3-5 minutes initially during purging. The goal is a
minimum to no drawdown. Adjust pumping rate as appropriate to accomplish this goal. In
any event, the pumping rate should not exceed .5 liters/minute.
Use field parameters of temperature, conductivity, and turbidity to determine when the purge
is adequate and when to sample per FP 6 and 10. These field procedures call for the use of
off line field instruments to check these parameters. These parameters should be recorded
in the field notebook every 5 minutes after stabilizing the pump rate. The sample can be
taken when conductivity is within 3% and turbidity within 10% for three consecutive
readings. If turbidity only fails to meet this requirement within a reasonable time period, then
the sample can be taken if the other parameter meets the requirement.
Collect two 1-liter samples from each well after field parameters have stabilized. The
samples should be collected into a standard glass bottle with a Teflon lid. To preserve the
sample, place the labeled and sealed bottles in a cooler with ice (samples should be cooled
to about 4 degrees C) while awaiting transport and during transport to the lab.
For each group of 10 samples provided to the lab, a duplicate field sample, a field blank,
and an extra volume of sample for a MS/MSD pair should be included.
Monitoring Well MW-1
Monitoring well MW-1 is a well that is cased with 6" steel to a depth of 13.5' below
ground level and is open in rock to a depth of 42.0' bgl. The hole was initially cored and
the core log indicates vertical and horizontal fractures from 8.5' to 14.5' bgl, and broken
rock zones at 16' and 26' bgl. A video-log is available for this well and an open solution
conduit 1" to 2" in diameter is clearly visible at 16.1' bgl developed along a bedding
plane. The zone at 26' bgl appears to be a shale parting and did not appear to be open
in the video-log. The packer tests indicate that the maximum amount of hydraulic
conductivity was 13.5' to 18' bgl. The packer test of the interval 13.5' to 42' had less
hydraulic conductivity than the 13.5'to 18' interval, indicating that the solution conduit at
16.1' bgl (elevation 661.59' amsl) is the water producing zone. The 1988 maximum
water column measured was 37.5', which would be 55 gal for one well volume. Over
purging of 5 well volumes could be expected to produce about 275 gallons.
Monitoring Well MW-3s
Monitoring well MW-3s is a well installed in unconsolidated sediments. The total
borehole depth is 6.8' bgl. It is screened with a 3' screen of 2" PVC from 3.1'to 6.1' bgl.
The maximum water column in 1988 was 2.86' and, including the water in the gravel
pack, the purge volume for one well volume was 2 gal. Over purging of 5 well volumes
could be expected to produce about 10 gallons.
Monitoring Well MW-3I
Monitoring well MW-31 is a well installed in the upper part of the bedrock. The bedrock
part of the well is from 7.5' to 17.5' bgl, which is also the 2" PVC screen interval. Well
MW-3d, right next to it was cored initially and the core logs indicate that the first 10' of
bedrock had the highest concentration of fractures. This was the apparent rationale for
the installation of well MW-31. The 1988 maximum water column was 13.13' and the
well volume was 6 gal. Over purging of 5 well volumes could be expected to produce
about 30 gallons.
Monitoring Well MW-3d
Monitoring well MW-3d was initially a core advanced to 45' bgl. As mentioned above,
the core log notes the majority of the fractures were in the first 10' of rock encountered.
A clay isyer was noted at 19' to19.12' bgl, which was interpreted to be a clay filled
fracture. The well is screened with 2" PVC from 29.8' to 39.8' bgl, but no rationale is
given in the description of why this interval was chosen. Irregular fractures are noted on
the core log from 30.8' to 31.4'. This may be the zone making the water in this well.
Packer tests, however, indicate that there was no flow when intervals 24.5-31, 31.5-38,
and 40.5-45 were tested. Nevertheless, the maximum water column in 1988 was 31.31'
and one well volume was calculated to be 10.5 gallons. In the March 10, 1988 sampling
event 5 well volumes were purged for a total of 52.5 gallons. It is expected that this
could be the volume again.
Monitoring Well MW-4
Monitoring well MW-4 is a well cased to about 14'bgl with 6" steel casing and open in
rock from 14' to 45.5' bgl. The hole was initially cored and the core log indicates a mud-stained fracture at 14.45' bgi. A video-log is available for this well, and an open 1" to 2"
diameter solution conduit can be clearly seen at the 14.45' bgl level. The packer tests
show the maximum hydraulic conductivity at the 14-16 interval and less hydraulic
conductivity when the interval tested is 14-45.5. This indicates that the conduit at 14.45 '
bgl (elevation 663.64' amsl) is the water-producing zone. The 1988 maximum water
column was 43', which makes one well volume to be 65 gal. Over-purging of 5 well
volumes could be expected to produce about 325 gallons.
Monitoring Well MW-5I
Monitoring well MW-5I is a well that is drilled 9.5' through clay soil and then 10.5' into
rock. The 2" PVC well screen is from 10' to 20' bgl, but the gravel pack extends up to
8' bgl. A possible fracture is mentioned in the core log at 16' bgl, but the rock unit is
identified as shale. Because the gravel pack includes the soil-bedrock interface, it is
likely that this is the water-producing zone for the well. The top of this shale unit is seen
as perching the spring horizon that appears along the east side of the former tertiary
lagoon. The 1988 maximum water column was 12.08' and one well volume was
calculated to be 7 gal. Over-purging of 5 well volumes could be expected to produce
35 gallons.
Monitoring Well MW-5D
Monitoring well MW-5D was initially cored to 55.5' bgl. It is screened from 20' to 30' bgl
with 2" PVC. No rationale is given in the description of why this interval was chosen and
no fractures or voids are noted in the core logs. There is a limestone-shale contact at
27' bgl (elevation 665.99 amsl) where a solution conduit would likely develop. The
hydraulic conductivity calculated from the slug test is 10-3 cm/sec. This value is
comparable to the values calculated in other wells on the site with bedding plane
conduits. The maximum 1988 water column was 21.92' and a well volume was
calculated to 8.3 gal. In the March 9, 1988 sampling event five well volumes were
purged for a total of 43 gallons. This amount could be expected again.
Monitoring Well MW-6
Monitoring well MW-6 is a well cased to 23.5'bgl with 6" steel casing and open in rock
from 23.5' to 51.5' bgl. The hole was initially cored and the core log indicates a
solution-enlarged horizontal fracture at 21.5' bgl. No video-log is available for this well.
The packer tests show the maximum hydraulic conductivity at the 23.5' to 25'interval and
less hydraulic conductivity when the interval tested is 23.5-51.5. This may indicate that
the conduit at 21.5' bgl (elevation 676.39'amsl) is the water-producing zone, even
though it is seemingly cased off. The March 9, 1988 field log reports that the well went
dry when one well volume was purged, but that water could be heard trickling into the
well as the level was drawn down. The 1988 maximum water column was 36.76', which
makes one well volume to be 55 gal. Over-purging of 5 well volumes could be expected
to produce about 275 gallons.
Monitoring Well MW-7
Monitoring well MW-7 is a well cased to 13' bgl with 7" steel casing and open in rock to
39' bgl. The hole was drilled with air rotary and air bubbled in the creek during drilling.
A video-log is available for the well and clearly shows an open solution conduit
developed on a bedding plane at 14'bgl. The packer tests show no flow when the
interval tested is 17.5' to 39', but shows flow when the interval tested was 13.5' to 39'.
This indicates that the conduit at 14' bgl (elevation 658.01' amsl) is the water-producing
zone in the well, although at high flood levels, creek water could backflood the well. The
maximum 1988 water column was 33.09' and one well volume was 48 gal. The field log
for the March 10, 1988 sampling event states that the well went dry after one well
volume was purged. Over-purging 5 well volumes could be expected to produce about
240 gallons.
Monitoring Well MW-8
Monitoring well MW-8 is a well cased to 10' bgl with 7" steel casing and open in rock to
45' bgl. The hole was drilled with air rotary and no core record is available. No video-log
is available for the well either. The packer tests show no flow when the interval tested is
40' to 45', but shows flow when the interval tested was 11' to 45'. The maximum 1988
water column was 44.04' and one well volume was 65 gal. The field log for the March
10, 1988 sampling event states that the well recovered quickly. Over-purging 5 well
volumes could be expected to produce about 325 gallons.
|
