HomeMy WebLinkAbout18- Task Order - Tetra Tech, Inc. - Modification to 2018 Operation and Maintenance Task Order to Address Recommendations for System Evaluation at the Bozeman Landfill TETRA TECH
TASK ORDER
MODIFICATION TO 2018 OPERATION AND MAINTENANCE TASK ORDER TO
ADDRESS RECOMMENDATIONS FOR SYSTEM EVALUATION
BOZEMAN LANDFILL
April 6, 2018
CLIENT: CONSULTANT:
The City of Bozeman Tetra Tech, Inc.
P.O. Box 1230 851 Bridger Drive, Ste 6
Bozeman, Montana 5971 1-1 230 Bozeman, MT 59718
Attention: Mr. Rick Hixson Attention: Mr. Kirk A. Miller
INTRODUCTION
The purpose of this task order is to implement Recommendations 2, 4 and 5 from Tetra Tech's
Initial Remedial System Evaluation Report (dated March 9, 2018). These recommendations are
directed at improving the effectiveness of the landfill gas extraction and soil vapor extraction
systems currently operating at the landfill. All five recommendations are listed below:
Recommendation 1 — Conduct two additional groundwater monitoring events in 2018;
• Recommendation 2 — Conduct test of SVE radius of influence;
• Recommendation 3 —Adjust SVE air flow rates;
• Recommendation 4— Replacement of landfill gas extraction well GW-18; and,
• Recommendation 5— Surface Emissions Sweep of Unlined Cell.
Recommendation 1 is being addressed by Tetra Tech's 2018 Groundwater and Perimeter
Methane Monitoring Task Order, which is already under consideration by the City.
Recommendation 3 can be completed under Tetra Tech's existing 2017-2018 Remediation
System Oversight Task Order (approved October 17, 2017), Tetra Tech job number 114-
720487A. Therefore, only Recommendations 2, 4 and 5 are addressed by this Task Order
Modification. Tetra Tech proposes to modify our existing Remediation System Oversight Task
Order, referenced above, to include the scope of work and budget outlined in this Task Order.
This will serve to consolidate Tetra Tech's landfill services to just two Task Orders.
SCOPE OF SERVICES
This task order includes the following three tasks:
• Task 1 -Evaluation of Radius of Influence for Soil Vapor Extraction Wells.
• Task 2 - Installation of New Landfill Gas Extraction Well and Pump to Replace GW-18.
• Task 3—Conduct a Surface Emissions Sweep of landfill cover.
The scope of work and costs to conduct these three tasks are outlined below.
Tetra Tech
851 Bridger Drive, Suite 6; Bozeman, MT 59715
Tel 406.582.8780 Fax 406.582.8790 tetratech.com
Task Order—Modifications to 2018 Operation and Maintenance Task Order
April 6, 2018
Task 1 Evaluation of Radius of Influence for Soil Vapor Extraction Wells
Additional vacuum monitoring points are needed to confirm that a continuous zone of influence
has been created along the south property boundary by the SVE system. There are a limited
number of vacuum monitoring points available to evaluate the radius of influence created by the
SVE system. Drilling new monitoring points is expensive. Therefore, we recommend testing the
radius of influence of the SVE wells by conducting short-term shutdowns of some SVE and Al
wells and allowing pressures and vacuums to equilibrate prior to conducting a round of vacuum
measurement in nearby monitoring wells and the shutdown SVE wells. This will allow a better
estimation of the vacuum radius of influence created in each SVE well or groups of SVE wells
across the south boundary of the landfill property. Several iterations of the test will be conducted
with different SVE wells shut down for each test iteration to allow data to be collected across the
entire width of the SVE system. We propose to use these results to identify the radius of vacuum
influence along a larger portion of the south property boundary and to confirm that adequate
capture of landfill gas (LFG) migration is being achieved.
Existing vacuum data supports an average radius of influence of approximately 50 ft., however, it
likely is variable across the south boundary of the landfill and the radius may well be larger than
our estimate. Two primary tests are proposed (Test 1 and Test 2) to evaluate variability of the
influence between different SVE wells and whether capture of soil gases is occurring in the areas
with larger expanses between SVE wells. Slight modifications will be made part way throughout
the tests to further isolate areas between wells (Tests 1 A and 2A). SVE wells that have been
temporarily shut down and all air injection wells will be used as vacuum monitoring points,
increasing the number of data points. This will also allow BSV soil gas probes or BLG methane
monitoring wells that are close to SVE wells to provide data on the affects from SVE wells at a
greater distance.
Tetra Tech will prepare a study plan that outlines the specific SVE wells to be shut down for each
of the tests and where and when air emission air quality tests will be collected. The air quality
samples are intended to evaluate whether changing the SVE air flow impacts the concentrations
of volatile organic compounds extracted by the system. The SVE Pilot Test study plan will include
identification of the areas that each test is expected to isolate so that radius of influence estimates
can be calculated. Our initial planning indicates the following approach to these pilot tests:
Test 1
The following wells will be shut down then vacuum levels in surrounding wells will be monitored
until equilibrium is established:
• SVE wells 2, 4, 7, 12 and 16.
• All Air Injection Wells
This will provide data on the radius of influence between SVE-8 and 9, SVE-14 and 15, SVE-1
and 13, SVE-5 and 6, and SVE-10 and 11. Based upon the results of Test 1 we may conduct Test
1A, wherein, we will shut down the same SVE and Al wells as for Test 1, as well as several
additional wells (e.g., SVE-3 and 6).
Test 2
The following wells will be shut down then vacuum levels in surrounding wells will be monitored
until equilibrium is established:
• SVE wells 5, 8, 10, 13 and 14.
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Task Order— Modifications to 2018 Operation and Maintenance Task Order
April 6, 2018
• All Air Injection Wells
This will provide data on the radius of influence between SVE-3 and 4, SVE-4 and 11, SVE-11
and 12, SVE-2 and 6, SVE-1 and 7 and SVE-15 and 16. Based upon the results of Tests 1 and 2
we may conduct Test 2A, which will shut down the same wells as Test 2, as well as several
additional wells (e.g., SVE-1, 4, 6 and 9).
After each set of SVE wells and the Al wells are shut down, vacuum measurements will be
collected every two to four hours until it appears that vacuum levels are stabilized. This condition
will be maintained for up to 12 hours until the next test is initiated. Weather changes may change
vacuum readings, so this may cause a delay in initiation or completion of some tests. At least two
staff persons will be needed to adjust the SVE and Al wells and to collect the vacuum
measurements.
Tetra Tech will use a Photo ionization detector and/or flame ionization detector to sample air in
the SVE discharge (prior to the flare) and perhaps from a few individual SVE wells to evaluate
changes in VOC concentrations. The frequency and location of this sampling, as well as the need
for any laboratory samples, will be developed in the Study Plan.
Upon completion of each test, the data will be briefly reviewed in the field to identify areas where
the data is inconclusive, which may dictate the need for an additional test. After completion of the
tests the data will be compiled into a data base and presented graphically in both plan and
section, so that radius of influence can be evaluated for both aerial distribution and vertical
distribution. Based upon evaluation of the data, Tetra Tech will develop recommendations, if
warranted, for adjustment of flow rates in SVE well, installation of additional vacuum monitoring
points and/or installation of additional SVE wells.
Task 2 Installation of New Landfill Gas Extraction Well and Leachate Pump
Well GW-18 is the only landfill gas well in the field that needs a leachate pump but does not have
a pump. This is due to the casing having been bent or broken, which precluded installation of a
pump. Attempts to fix this problem have been unsuccessful, therefore, there is standing water in
GW-18, which limits the ability of the well to capture LFG. A new six-inch diameter LFG extraction
well will be installed (likely 12-inch boring diameter) to replace GW-18 and it will be fitted with a
leachate pump to increase the effectiveness of LFG extraction and leachate removal from this
area.
Tetra Tech will prepare Plans and Specifications for the new well and obtain bids from qualified
drillers. The Plans and Specifications will essentially mirror those used for the installation of the
new LFG wells in 2014, however, the drilling equipment requirements will be modified. The cost to
mobilize the specialized drilling equipment used in 2014 from outside the region would likely be
much higher than the cost to drill the well, therefore, more locally available drilling methods (e.g.,
air rotary) will be allowed.
Tetra Tech staff will provide field oversight of the drilling contractor for the drilling and well
installation. A local contractor will be retained to complete the piping connections between the
existing LFG collection system and the new well. Most of the costly piping, valves and pumps are
left over from the 2014 construction, hence, new material costs will be limited.
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TETRA TECH
Task Order—Modifications to 2018 Operation and Maintenance Task Order
April 6, 2018
Task 3. Conduct Surface Emissions Sweep of Unlined Cell Cover
A surface emissions sweep will be conducted to map landfill gas emissions through the landfill
cap and evaluate if there are areas within the 32-acre Unlined Closed Cell that need upgrades to
the cap. These areas of the cap may also be susceptible to infiltration of surface water. The scan
will entail running a volatile organic analyzer on a grid pattern over the surface of the Unlined
Closed Cell and recording concentrations of VOCs. The survey will be conducted after surface
soils and the cover have dried out adequately to allow evaluation of worst case conditions (winter
snows and saturated soil materials tend to reduce the flow of LFG out of the cell).
The methods used for the surface emissions sweep will be similar to what is required by the New
Source Performance Standards (NSPS) for qualifying Municipal Solid Waste (MSW) Landfills,
however, this sweep is not being conducted as a compliance requirement.
The designated sweep area will be traversed using a survey pattern as described in Subpart
WWW of USEPA's NSPS in intervals of thirty (30) meters along a serpentine pattern.
Measurements will be collected using a TVA-2020 Flame Ionization Detector (FID) with a range of
1 ppm to 100,000 ppm Methane (CH4). The TVA-2020 will be calibrated with a span gas
concentration of 500 parts per million by volume (ppmv) CH4 and a calibration gas containing 20
to 22% oxygen. The Site's background concentration will be determined by moving the probe inlet
upwind and downwind outside of the limits of waste and at a distance of at least 30 meters from
perimeter wells. Instantaneous measurements of methane concentrations will be monitored
within 5 to 10 centimeters (=2—4 inches) immediately above the surface.
Areas showing elevated VOCs may indicate that improvements to the soil cover are necessary to
better contain methane and to reduce surface water infiltration. The survey results will be
summarized in a brief report and recommendations for further actions will be provided.
PERIOD OF PERFORMANCE
Assuming approval of this Task Order by April 30, 2018, Tetra Tech's anticipated schedule to
complete the above described activities will be the following:
Deliverable Completion Date
Complete Study Plan for SVE Pilot Test May 11, 2018
Complete SVE Pilot Test Field Work May 25, 2018
Submit Draft SVE Pilot Test Report to City June 15, 2018
Submit LFG replacement well design to City May 18, 2018
Contract with Driller for LFG replacement well June 15, 2018
Complete LFG replacement well July 13, 2018
Conduct Surface Emissions Sweep August 2018
Submit Surface Emissions Sweep Report September 2018
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TETRA TECH
Task Order— Modifications to 2018 Operation and Maintenance Task Order
April 6, 2018
COSTS
Estimated costs to complete the foregoing scope of services are in shown below:
Estimated Costs
2018 Modification to Operation and Maintenance Task Order
Bozeman Landfill
Task Description Estimated Cost
Task 1. SVE Pilot Test _ $23,703
Task 2. Replacement of LFG Well $20,863
Task 3. Surface Emissions Sweep $7,188
Total $51,753
The services conducted and invoicing will be on a time and materials basis. A detailed cost
estimate can be provided upon request.
SPECIAL CONDITIONS: Execution of this Task Order constitutes acceptance of all terms and
conditions contained in Tetra Tech's Professional Services Agreement with the City of Bozeman,
dated April 15, 2014.
CLIENT: CONSULTA T:
1
Cityof Bozeman Tetra Tech 1
By: By:
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Printed Name: Printed Name: Kirk A. Miller
Its: ` ' ,t., ` Its: Senior Project Manager
Date: J114e _�} 1 Date: April 6, 2018
NOTICE OF CONFIDENTIALITY This Task Order(including attachments) contains information confidential to Tetra
Tech, Inc., its subsidiaries, and subcontractors. It is intended only for City of Bozeman to consider Tetra Tech
providing professional services at the Bozeman Landfill. Any other use is prohibited, without the prior written consent
of Tetra Tech.
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TETRA TECH