Their Science
We begin with a discussion of the sole pillar that supports the entire 2017 Environmental Assessment; the claim of relatively impermeable subsoils which will supposedly guarantee that waste cells remain sealed forever. The Waterkeepers find that this claim of impermeability unsupportable. The first claim of impermeability was made way back in 2005 by MGI in their assessment for the original debris site. Despite what the 1969 soil map says, "impermeability" at AHC&D seems to be an article of faith at Nova Scotia Environment.
MGI carried out their
Hydrogeological testing on July 28th and 29th 2004, to help determine suitability of
the site for industrial approval and establishment of Arlington Heights Construction Debris (AHC&D). They drilled a bore hole, six test wells, and
dug six test pits. The wells were 7.6m
or bedrock deep. The test pits were 3m
deep. Soil samples were taken from all
excavations and analyzed for moisture content, Atterberg Limits, and
grain size analysis. Oddly, though the
sampling was extensive, a fundamental suite of necessary data, permeability
tests, was never recorded.
One month after the samples had been tested and the results
reported, assessors returned
to the site to collect data to augment the MGI report. The purpose of this additional testing was to
obtain soil samples for a permeability test. Two additional test pits were dug.
From the first, a Shelby tube sample near the 11’ mark and
another at the 18’ mark were extracted both from relatively pure clay pockets in the matrix.
The soil profile of pit #1 was recorded as follows:
- 1-12” topsoil
- 12-26” silty sand
- 26”-42” hardpan-compacted gravel and sand
- 42”-11’ clay-silt, gravel and stone present throughout
- 11’-bedrock silt-clay, gravel and stone present throughout
The pit also showed sandy horizons at the 26” and 11’
levels.
There is no evidence that pit#2 was ever investigated except to note the presence of a sandy horizon at the 11’ level, similar to pit #1. The walls of the pit were noticeably damp, though moisture content was never tested. The pits were left open over a rainless weekend.
The 11’ tube sample tested 1.5*10‾ 8 cm/sec; the 18” tube
sample tested 5*10‾8 cm/sec. These
permeability values are extremely low; unrealistically low. These values mean, in layman’s terms, that
the rain which fell in the wetland below the dump, (which, we remind you is the
designated receptor for internal and external asbestos cell drains, and which
also acts as our community reservoir) traveled through the soil for 200,000
years before it made it to a spring less than 1 kilometer away.
Permeability values like these mean that rainwater could never penetrate the subsoil before it ran off as surface drainage, or evaporated, or was consumed in biotic transpiration. Without subsoil recharge, the brooks would be as dry as bones. These are all clearly improbable circumstances that question the accuracy of the tested permeability value. It is odd that no review of the report ever twigged to the questionable value attached to the sample. Both Environmental Assessments offered investigators hints to beware the results: in 2017 the moisture content of the samples was “misleading”; in 2005, MGI disclaimed credit for the results by repeatedly advising that the samples were taken by a nonscientist and NOT by MGI.
Permeability values like these mean that rainwater could never penetrate the subsoil before it ran off as surface drainage, or evaporated, or was consumed in biotic transpiration. Without subsoil recharge, the brooks would be as dry as bones. These are all clearly improbable circumstances that question the accuracy of the tested permeability value. It is odd that no review of the report ever twigged to the questionable value attached to the sample. Both Environmental Assessments offered investigators hints to beware the results: in 2017 the moisture content of the samples was “misleading”; in 2005, MGI disclaimed credit for the results by repeatedly advising that the samples were taken by a nonscientist and NOT by MGI.
There is more evidence to discredit this sampling. Any rigorous scientific investigation of site
permeability would require far more than a single data point. Multiple tests would need to be accurate,
reviewed and be repeatable. However, no
such tests were done nor was any corroborating reference or supporting evidence
from any other line of inquiry ever presented to bolster the impermeability
claim. Beyond this, the proponent adds the unsupported argument that this permeability value obtains over the
entire study area. It is quite
clear that water is moving freely through the clay/gravel matrix. The evidence comes from the very test pit
that supposedly “proved” that the soil was impermeable. Test pit #1 collected more than 2600 imp
gallons of water over a rainless weekend and filled to a depth of almost 8
feet. That is enough water to power a domestic water supply and it all came
through the clay matrix that the EA calls “impermeable”.
The 2005 report suggested that the bulk of water may have moved through the above mentioned sandy horizons, while noting that the pit walls were all uniformly damp. Also, the limited value of lab sample testing is illustrated by the suspect data obtained from the test pit under discussion here. The sample must be collected and handled properly or the Shelby tube system will compress and seal tiny natural passages that develop by cycles of wet and dry, or by the action of frost in clay samples, and thereby produce incorrect test results. Samples must also be maintained at proper hydration levels to record valid Falling Head test data. Beyond all this, test results only obtain within the sample itself; they provide no information whatsoever about the surrounding soil.
The 2005 report suggested that the bulk of water may have moved through the above mentioned sandy horizons, while noting that the pit walls were all uniformly damp. Also, the limited value of lab sample testing is illustrated by the suspect data obtained from the test pit under discussion here. The sample must be collected and handled properly or the Shelby tube system will compress and seal tiny natural passages that develop by cycles of wet and dry, or by the action of frost in clay samples, and thereby produce incorrect test results. Samples must also be maintained at proper hydration levels to record valid Falling Head test data. Beyond all this, test results only obtain within the sample itself; they provide no information whatsoever about the surrounding soil.
Since no reliable data about permeability is provided by the
proponent or any of her agents, the Waterkeepers designed and carried out a
slug test permeability study of their own.
The results of that testing follow. In the data tab, you will find a summary of a series of
slug tests and associated data performed and collected at West Arlington on March 3, 4, and 5 2018.
Citizen Science
At West Arlington, Annapolis County
By James McCurdy for
Annapolis Waterkeepers
March 5, 2018
This study is designed to provide credible data to establish
in-situ measurements of water flow rates and hydraulic conductivity in North
Mountain Clay at West Arlington. No
information on this topic currently exists in the literature save a single suspect
citation in AHCD EA 2017.
Our personal experience with the N.M. clay contradicts the
MGI data cited in the EA. We do not
believe that the N.M. clay is “relatively impermeable” but rather freely admits
the passage of water. Our belief is founded on much physical evidence. Postholes, drainage ditches, waterlines and
road cuts all weep substantial amounts of water. The water bleeds through cobble, sand, and
gravel inclusions in the clay matrix.
The Cobble, Sand and Gravel (CSG) comes from two sources: first, the natural differential weathering of the basalt bedrock. Harder bits of slow-weathering basalt are incorporated into the faster-weathering soft clay components of the soil. This geologic feature is present at all depths of the subsoil as a captured feature of soil building. It may be seen in the cobble lined stream beds and the cobbled and graveled surface of exposed soil. The second source of CSG in the clay matrix is glacial till. Pleistocene glaciers have spread South Mountain granite across the entire North Mountain landscape. Seasonal advances and retreats of the glaciers over thousands of years have mixed everything from granite boulders the size of cars to fieldstones to pure sand into the weathering basalt matrix.
The evidence of granitic inclusions is apparent everywhere across the site: granite stones in the rock piles, sandy bars in the brooks, granite gravel on the top of exposed soils. The inclusions may form substantial veins of gravel in the clay that feed vigorous springs farther down the mountainside. By these direct observations, glacial deposition is confirmed as a prominent feature of Arlington soils. However, the certain presence of glacial inclusions in the clay matrix of the dump site is never mentioned in the EA, even though these inclusions are a global and prominent drainage feature of the Arlington subsoil.
Accordingly, we felt the necessity to test Hydraulic conductivity for ourselves. We have established a baseline that extends from the Granville line 500m to the West, roughly parallel and adjacent to AHCD property. Along this line we have established five shallow wells (1.10m+- deep, 17.78cm diam) approximately 125m apart. All wells extended well below the water table. The wells were bailed dry and allowed to fill for 20min. Since the study was intended to measure subsoil conductivity only, collars were installed at the “A” horizon to exclude all surface water from entering the test wells. The collars proved unnecessary except for wells 4 and 5, which were situated downslope from AHCD drainage outfalls into the receptor wetland, where substantial amounts of surface water flow were observed. The depth of the well and the depth of the water, both measured from the baseline of the water table, were recorded and used as data for Hooghoudt’s conductivity equations:
K=F(Ho-Ht)/t
Where
- K=horizontal saturated hydraulic conductivity (m/day)
- H=depth of water level in well relative to the water table in the soil (cm)
- Ht=H at time t (seconds)
- Ho=H at time t=0 (seconds)
- T= time since first measurement of H as Ho (seconds)
And,
F=4000r/h’(20+D/r)(2-h’/D)
Where
- r=radius of cylindrical hole (cm)
- h’= average depth of the water level relative to the water table in the soil : h’=(Ho+Ht)/2
- D=depth of the bottom of the well relative to the water table in the soil
In all wells, the water seepage was observed to originate
evenly on the sides of the boreholes.
Soil samples were taken from the top of the subsoil, the .5
meter depth, and the 1 meter depth.
Measured volumes of these were washed to remove the clay. The volume of cobble, sand and gravel (CSG) captured by a 1.5mm screen
filter was compared to the volume of the original sample to obtain a CSG volume
percentage for each soil sample.
The test results clearly do not describe impermeable subsoil. Rather, they describe a matrix of clay
infused with CSG inclusions that is remarkable not for its sealing properties,
but for its ability to freely admit the passage of water. The clay matrix hosts a broad, dynamic,
moving aquifer that is charged and pressurized by subsoil flowage from the
Rumsey lake watershed that does not fall into the Poole brook drainage on the
West or the Granville Line Brook drainage to the East. As can be seen from the conductivity tests,
the mean conductivity across all five test wells was 3.8x10‾4 cm/sec. This value falls squarely in the “semi
permeable” range, and describes subsoil four orders of magnitude (ten thousand
times) more porous than the 2005 test.
The reason for the
porosity is the cobble, sand, and gravel (CSG) included in the clay
matrix. The mean percentage of CSG ›1.5mm
by volume across all wells at all depths was 27%.
This study is more reliable than the 2004 tests because it
measures the actual “in-situ” conductivity in real time. In addition, there is no opportunity to do
any “selective” sampling. The
Waterkeeper’s study is accurate, rigorous, repeatable, and peer reviewed. However, there are limits to the methodology
and the conclusions it suggests. Only
the top four feet of subsoil were tested. There is some hint from the data that
the amount of cobble, sand and gravel (CSG) within the clay matrix may decline
slightly with depth, but there is not enough evidence in the Waterkeeper’s
study to establish a clear trend.
Neither is there any reason, given the methods of deposition, that the
amounts of CSG should vary greatly with depth.
Still, the amount of CSG and permeability at depths greater than four
feet remains untested.
We call on the Nova Scotia Environment to organize real-time slug tests to determine true conductivity values from the 4’ to 15’ depths across the site. We are confident that such tests will reveal conductivities that cannot support the safe disposal and sealing of asbestos waste. In any case, additional testing is a moot point - the top four feet of subsoil clearly cannot be used in any part of the sealing process. Unfortunately it has already been used to provide a seal that it cannot possibly manage.
Another issue is the size of the test wells. They were 1+cm larger than the size recommended for the conductivity formulas used. K, however, is only slightly sensitive to the minimally oversized bore hole and returns values slightly weighted in favor of impermeability. The small difference does not alter the findings in any significant way.
Finally, the study wells were only adjacent to, and not actually on the dump property. Since no variation of results was noted over a distance of 500 meters in an East-West direction along the study baseline, it is assumed that no significant variation occurs in a North-South direction either. The average distance from the test wells to AHCD property is 2 meters. The distance from the wells to disposal cells areas is from 200 to 300 meters. The distance from the nearest well to the disposal drain outfall (well #4) is about 60 meters.
We call on the Nova Scotia Environment to organize real-time slug tests to determine true conductivity values from the 4’ to 15’ depths across the site. We are confident that such tests will reveal conductivities that cannot support the safe disposal and sealing of asbestos waste. In any case, additional testing is a moot point - the top four feet of subsoil clearly cannot be used in any part of the sealing process. Unfortunately it has already been used to provide a seal that it cannot possibly manage.
Another issue is the size of the test wells. They were 1+cm larger than the size recommended for the conductivity formulas used. K, however, is only slightly sensitive to the minimally oversized bore hole and returns values slightly weighted in favor of impermeability. The small difference does not alter the findings in any significant way.
Finally, the study wells were only adjacent to, and not actually on the dump property. Since no variation of results was noted over a distance of 500 meters in an East-West direction along the study baseline, it is assumed that no significant variation occurs in a North-South direction either. The average distance from the test wells to AHCD property is 2 meters. The distance from the wells to disposal cells areas is from 200 to 300 meters. The distance from the nearest well to the disposal drain outfall (well #4) is about 60 meters.
It is also possible to estimate soil hydraulic conductivity
values by means of grain size analysis.
In the 2004 study six samples were analyzed by grain size. Of these, only three recorded the screen size
for tenth percentile passage. Test pit
two and test pit five recorded screen size of .001 for tenth percentile passage
at a depth of 2.4-3m. Monitoring well #
6 recorded .003 screen size for tenth percentile at a depth of 3-3.6m. These screen sizes convert (Hazen) to
estimated K values of 1-1.5x10‾5 cm/sec. and 9-13.5x10‾5cm/sec. The values fall in the semi-porous range of
soil classification though they are slightly lower than those obtained in the
Waterkeeper’s study. These K values
estimated from grain size analysis further invalidate the reported data. The difference between bona fide Waterkeeper
and 2004 values is so great (three magnitudes) that any certified researcher
would have been skeptical.
The net result of the
study and associated data is to disqualify the argument that Arlington subsoil
is sufficiently impermeable to serve as an effective and safe sealer for
asbestos disposal cells.
Continued use of this material is a danger the health and welfare of the citizens who draw drinking water from the North Mountain Watershed and Wetland Reservoir.
Continued use of this material is a danger the health and welfare of the citizens who draw drinking water from the North Mountain Watershed and Wetland Reservoir.
The Waterkeepers question NSE’s approval of this project.
We express our concern in the form of questions, that we might receive a
considered response.
In Conclusion
- Why did no one grasp the fact that the 2004 sample was probably incorrect, especially when confronted with abundant and obvious physical evidence before their eyes and under their feet? Why did no one attempt to, or require the applicant to provide better data about the true permeability and composition of the subsoil?
- Why did no one realize that large amounts of wetland had been filled to accommodate the AHCD project, even though evidence of this fact abounds in the EA, and is displayed in full view all around the site?
- Why did no one realize that the wetland designated as the “receptor” area for outfall drains from the asbestos beds was actually a drinking water reservoir for all the downslope residents?
- Why did no one realize that the natural drainages that power the wells and springs of the residents of St. Croix Cove and beyond all originate in the wetland that now receives potentially contaminated AHCD waste water runoff?
- How could the Nova Scotia Environment have ever considered that it was safe to site a toxic waste dump in the middle of a watershed and drinking water reservoir?
- Why did Nova Scotia Environment never avail itself of the wisdom and experience of the residents when considering approval of this project? Consultation would have helped them formulate a more appropriate decision.
- Why has Nova Scotia Environment been so lax in verifying what it should know are likely to be “colored” claims and incomplete reporting in this EA registration? Citizen groups like the Waterkeepers should not have to do Nova Scotia Environment's work after the fact.
- And finally, why does Nova Scotia Environment seem so eager to enable industrial development of previously pristine natural freshwater resources?
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