HomeMy WebLinkAbout10-06-20 City Commission Packet Materials - C19. TO Revision 1 for FY21 Monitoring at Bozeman Landfill
Commission Memorandum
REPORT TO: Honorable Mayor and City Commission
FROM: Shawn Kohtz, City Engineer SUBJECT: Task Order – Revision 1 Evaluation of Hydrogeology and Refuse Distribution in Southeast Corner of Landfill to Task Order for
Fiscal Year 2021 Groundwater and Perimeter Methane Monitoring,
Assessment of System Performance and Effectiveness Bozeman Landfill AGENDA ITEM TYPE: Consent
MEETING DATE: October 6, 2020 RECOMMENDATION: Authorize the City Manager to execute the attached Task Order for Revision 1 Evaluation of Hydrogeology and Refuse Distribution in Southeast Corner of Landfill
to Task Order 2020-2021 Groundwater and Perimeter Methane Monitoring Assessment of
System performance and Effectiveness at the Story Mill Landfill. BACKGROUND: The purpose of this task order is to evaluate the persistence of volatile organic
compounds in the southeast corner of the Story Mill landfill. Based upon recommendations from the
2018/2019 Remediation System Evaluation report (March 11, 2020), we propose to conduct a
more detailed investigation of the hydrogeology in the southeast corner of the landfill and the distribution of refuse in the area to better understand the recent increase in volatile organic compounds in that area. This information will be used to identify revisions to the existing landfill gas extraction and/or soil vapor extraction systems. This need is triggered by observed increases
in volatile organic compound (VOC) concentrations near the corner of the landfill. Additional
remediation system upgrades may be needed in the future as a result of this investigation work. This task order will be implemented under the professional services agreement referenced here: http://weblink.bozeman.net/WebLink8/0/doc/63070/Electronic.aspx. UNRESOLVED ISSUES: None.
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FISCAL EFFECTS: The cost of this work will be $62,100.00. This work will be paid for with
solid waste funds dedicated to this purpose. Funds for this scope of work were budgeted with the
Commission approved Budget but were not allocated in the original task order. ALTERNATIVES: As suggested by the City Commission.
Attachments: Revision 1 Evaluation of Hydrogeology and Refuse Distribution in Southeast Corner of Landfill to Task Order 2020-2021 - Groundwater and Perimeter Methane Monitoring, Assessment of System Performance and Effectiveness
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Tetra Tech
851 Bridger Drive, Suite 6; Bozeman, MT 59715
Tel 406.582.8780 Fax 406.582.8790 tetratech.com
REVISION 1 EVALUATION OF HYDROGEOLOGY AND REFUSE DISTRIBUTION IN SOUTHEAST CORNER OF LANDFILL TO TASK ORDER 2020 - 2021 GROUNDWATER AND PERIMETER METHANE MONITORING ASSESSMENT OF SYSTEM PERFORMANCE AND EFFECTIVENESS
FOR BOZEMAN LANDFILL September 22, 2020 CLIENT: CONSULTANT: The City of Bozeman Tetra Tech, Inc. P.O. Box 1230 851 Bridger Drive, Ste 6 Bozeman, Montana 59711-1230 Bozeman, MT 59718 Attention: Mr. Shawn Kohtz, PE Attention: Mr. Kirk A. Miller INTRODUCTION
The purpose of this task order revision is to evaluate the persistence of volatile organic compounds in the southeast corner of the Story Mill landfill. These activities will be conducted between September 2020 and June 30, 2021 and are directed at meeting DEQ Solid Waste
rules and the requirements of DEQ’s June 6, 2014 letter requiring the City of Bozeman to conduct a Corrective Measures Assessment and implement remedial measures. This Task Order revises our May 26, 2020 Task Order that was approved by the City Commission in June 2020. Based upon recommendations from the 2018/2019 Remediation System Evaluation report (March 11, 2020), we propose to conduct a more detailed investigation of the hydrogeology in the southeast corner of the landfill and the distribution of refuse in the area to better understand the recent increase in volatile organic compounds in that area. This information will be used to identify revisions to the existing landfill gas extraction and/or soil vapor extraction systems. SCOPE OF SERVICES This task order includes Task 500-Evaluate hydrogeology and refuse distribution in southeast
corner of landfill. The scope of work for this task is outlined below. Task 500 Evaluate hydrogeology and refuse distribution in southeast corner of landfill
The 2018/2019 Remedial System Evaluation Report (dated March 11, 2020) identified increases in VOC concentrations in groundwater in well MW-17, including the appearance of methylene
chloride above Montana groundwater protection standards for the first time since a single occurrence in 2015. This indicates the need to improve landfill gas capture in the southeast corner of the landfill. This task will entail a brief evaluation into whether increasing air flow from nearby LFGES wells and/or installing one or two additional landfill gas extraction wells in that area will
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Revision 1 to Task Order – 2020 to 2021 Groundwater and Methane Monitoring and Assessment Bozeman Landfill, Bozeman, Montana September 22, 2020
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TETRA TECH
reduce VOC concentrations in groundwater in the southeast corner of the landfill. It will also evaluate the distribution of VOC impacted groundwater in the area in order to better understand the source of the VOC in MW-17. Tetra Tech will evaluate the source and distribution of the VOCs with particular focus on methylene chloride. We see two possible scenarios: landfill gasses are not being fully captured by the LFGES (GW-20 was removed from the system to accommodate the convenience site), or landfill gasses are migrating offsite along the eastern property boundary, contacting groundwater which allows phase transfer of VOCs, which subsequently migrate back onto the landfill site. Our analysis will include investigating the potential to adjust flows in nearby LFGES wells to affect a vacuum across a larger portion of the southeast corner of the property. This analysis will be based on the extent and thickness of refuse in the area. The possibility of installing a horizontal
LFG well in the thin areas of refuse will also be evaluated. To evaluate the possibility that VOCs are reaching groundwater upgradient of well MW-17, an offsite, a new upgradient monitoring well will be evaluated.
Tetra Tech will evaluate well logs from the following locations: SVE 8, -9, and -16, MW-5 and -17, BSV-9, and -13, BLG-1 and -2 and GW-10, -15, -19, -20 and -26 to identify interbeds, changes in lithology or other indications for preferential pathways for either landfill gas or groundwater. Based on this analysis, Tetra Tech will identify LFG, SVE, groundwater monitoring and methane monitoring wells where landfill gas/soil gas can be collected to map the distribution of evaluate potential offsite migration of LFG along eastern boundary of landfill. Following sample collection and laboratory analysis we will compile this new data with existing methylene chloride data from SVE or LFG gas samples. Typical sources of methylene chloride in landfills will also be researched and compared to historical information on past landfill disposal practices in this area of the landfill and possible degradation The data collected by this program will be used to identify if more groundwater monitoring wells
are needed in the area to better understand the source of the VOCs observed in MW-17, if flow from existing LFG wells can be adjusted to increase the capture zone without pulling oxygen into the cell, and if new LFG wells are needed. The use of horizontal wells in areas of thin refuse will
also be evaluated. Our recommendations will be submitted to the City, then based upon approval from the City, we will develop a scope of work for our recommendations. This might include developing specifications for drilling a monitoring well, modifying existing wells to act as LFG wells or installation of additional LFG wells. Tetra Tech will assist the City with contractor management, oversight and construction QC as needed. PERIOD OF PERFORMANCE Tetra Tech’s anticipated schedule to complete the above described activities will be the following: Technical memorandum presenting findings and recommendations for new well locations by January 31, 2021, final report and recommendations for remediation system operations by June 2021.
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Revision 1 to Task Order – 2020 to 2021 Groundwater and Methane Monitoring and Assessment Bozeman Landfill, Bozeman, Montana September 22, 2020
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TETRA TECH
COSTS Estimated costs to complete the foregoing scope of services are $62,100. This includes the costs for laboratory analysis and for a drilling contractor to install several new wells. Our costs 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: CONSULTANT:
City of Bozeman Tetra Tech
By: By: Printed Name: Printed Name: Kirk A. Miller Its: Its: Senior Project Manager
Date: Date: September 22, 2020 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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