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Home My WebLink AboutC5. Amend PSA Tetra Commission Memorandum REPORT TO: Honorable Mayor and City Commission FROM: Craig Woolard, Director of Public Works Richard Hixson, City Engineer SUBJECT: Amendment to Professional Services Agreement with Tetra Tech Inc. for work on Previously Installed Mitigation Systems in Bridger Creek Phase III. MEETING DATE: April 13, 2015 AGENDA ITEM TYPE: Consent RECOMMENDATION: Authorize City Manager to sign. BACKGROUND: The attached task order was prepared by Tetra Tech on behalf of the City of Bozeman to accomplish necessary modifications and upgrades to the sub-slab depressurization systems previously installed in homes in Bridger Creek Phase III. The proposed cost for this task order is $72,419.00. The actual costs will be paid once the work is completed. FISCAL EFFECTS: This work will be paid for with the City's Landfill Post-Closure Fund. ALTERNATIVES: As suggested by the City Commission. Attachments: Task Order from Tetra Tech Inc. (3copies) Cost estimate for Task Order Report compiled on: 3/31/15 143 TASK ORDER 2015 MITIGATION SYSTEM MODIFICATIONS BOZEMAN LANDFILL March 16, 2015 CLIENT: CONSULTANT: The City of Bozeman Tetra Tech, Inc. P.O. Box 1230 851 Bridger Drive, Ste 6 Bozeman, Montana 59711-1230 Helena, MT 59715 Attention: Mr. Rick Hixson Attention: Mr. Kirk A Miller INTRODUCTION Sub-slab depressurization systems (aka mitigation systems) were installed in 28 homes in the Bridger Creek Phase III subdivision during 2013 and 2014. These systems continued to operate and Tetra Tech periodically conducts inspections of the systems to confirm the fans are functioning, vacuum measurements meet objectives and the systems are in good working order. Tetra Tech periodically receives calls from homeowner concerned about noise, the appearance of the discharge piping on the exterior of the house, how their system is functioning and other matters. These homeowner contacts have identified several modifications to existing systems that warrant implementation. In three cases, it is primarily a change to the discharge piping location. For several homes, we have recently observed a decrease in vacuum levels beneath the slab of their home, indicating that depressurization may not be occurring to the desired level across the entire basement during the winter months. Hence, further investigation (i.e., additional vacuum monitoring points) or an expansion of the mitigation system in these homes is proposed. SCOPE OF SERVICES This task order includes the following work activities;  Addition of two new vapor extraction points and three new vapor monitoring points (VMP) in SAI -18.  Modification of both discharge pipes for the two existing mitigation systems in SAI-1 to carry discharge points above highest roof line. This may also require framing and siding to enclose the two new pipes.  Modification of discharge piping for existing mitigation system in SAI-17 to carry discharge point above highest roof line and add framing and siding to enclose the new pipe.  Modification of discharge piping for existing mitigation system in TI-5 to carry discharge point above highest roof line and add framing and siding to enclose new pipe. A larger fan may also be installed.  Check taping connections between plastic sheeting and foundation walls on homes with crawl space mitigation systems. Add new tape as needed to maintain good seal.  Respond to City requests for data, information or to attend meetings related to the project. 144 Task Order For Mitigation System Modifications Bozeman Landfill, Bozeman, Montana March 16, 2015 Page 2 of 3 Page 2 of 3  Continue to respond to homeowner requests for information, system monitoring, modifications and other issues. Modification of Mitigation Systems for Four Homes During our periodic inspection of mitigation systems in homes, we identify modifications that are warranted. These might include an additional VMP to confirm changes in vacuum levels or it might entail an additional vacuum extraction point. We have completed, or anticipate needing, modifications in the following homes:  SAI-18 was identified as having low vacuum levels in the subsurface during the winter of 2014/2015, hence, modifications were completed improve the distribution of vacuum beneath the home. This entailed the addition of two additional extraction points with associated piping connecting to the existing fan and piping. Three additional VMPs were also necessary.  The mitigation system for home TI-5 may also be modified to provide a larger fan and new discharge piping to the highest roof line of the house. We are waiting for homeowner concurrence on a proposed plan for this home.  The mitigations system for TI-3 may need a larger fan to improve vacuum levels during winter months. We are installing new VMPs in this home to better understand conditions beneath the house.  SAI-1 and SAI-17 will have new discharge piping installed that extends above the highest roofline. This will also entail the construction of framing around the new piping and the installation of siding to match the existing home siding. SAI-1 has two extraction points, so two discharge pipe systems will be replaced. These are both related to homeowner concerns about frost accumulation, noise and/or their desire to have the discharge point farther away from windows.  SAI-3 has seen lower vacuum levels beneath the basement slab, but higher levels in a crawl space, so an additional valve may need to be added to the system to balance flow between the two areas of the house.  Lower vacuum levels have been observed in SAI-8 and SAI-9 and additional VMPs are recommended to better understand the distribution of vacuum created beneath these homes.  Home mitigation systems that were installed in homes with a crawl space entail plastic sheeting laid across the bare soil. The plastic is connected to the concrete footings using a special tape that forms a seal around the perimeter of the crawl space. The tape needs periodic inspection to ensure the plastic sheeting is securely attached to the concrete foundation. We anticipate some replacement tape may be necessary in a few homes to address loose tape. Per DEQ Vapor Intrusion guidance, indoor air should be sampled one month after significant changes are made to a mitigation system. If the winter 2015 indoor air sampling event is conducted, it will cover this need for resampling since these mitigation systems modifications will be made in January through March. If the winter 2015 indoor air sampling event is not conducted, another Task Order may be necessary to cover resampling of these homes. DEQ guidance also calls for more frequent mitigation system inspections after significant system modifications. This will entail inspections after two weeks, one month, and then quarterly. This is similar to the frequency of inspections conducted when the systems were initially installed. 145 Task Order For Mitigation System Modifications Bozeman Landfill, Bozeman, Montana March 16, 2015 Page 3 of 3 Page 3 of 3 Response to Requests for information from Homeowners and City We periodically are contacted by homeowners to provide information, answer questions, inspect existing mitigation systems and conduct other tasks related to conditions in their home. In addition, we are also periodically requested to provide City staff with information, data or analysis related to the project. This task covers the anticipated level of response to these requests through August. It is based upon the level of effort we have experienced over the last six months. PERIOD OF PERFORMANCE Tetra Tech’s anticipated schedule to complete the mitigation system modifications is January through April 2015, depending upon homeowner access. The vacuum and indoor air sampling activities, including reporting will occur between February and May 2015. The responses to homeowner requests are likely to be ongoing, so a specific timeline cannot be projected. COSTS Estimated costs to complete the foregoing scope of services are $72, 419, as detailed in Table 1. The services will be conducted on a time and materials basis. Please note that our cost estimate uses new billing rates for work conducted after January 2015. 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 January 3, 1994 and Amendment Nos. 1, 2, 3, and 4 of the Professional Services Agreement dated July 31, 1995; January 1, 1996; March 17, 1997; and December 10, 2001, respectively. CLIENT: CONSULTANT: City of Bozeman Tetra Tech By: By: Its: Its: Senior Project Manager Date: Date: March 16, 2015 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. 146 TABLE 1 - ESTIMATED BUDGET 2015 MITIGATION SYSTEM MODIFICATIONS BOZEMAN LANDFILL BOZEMAN, MONTANA Date Submitted: 3/16/2015 Task 200 Mitigation System Modifications Field Work Units Rate Cost Project Manager/Senior Hydrogeologist, per hour 24 $180.00 $4,320.00 Assistant Project Manager/Hydrogeologist, per hour 8 $100.00 $800.00 Environmental Scientist, per hour 120 $100.00 $12,000.00 Field Technician, per hour 32 $75.00 $2,400.00 Administrative Personnel, per hour 8 $70.00 $560.00 Labor Subtotal $20,080.00 DIRECT COSTS Tetra Tech Vehicle Mileage, per mile 2,000 $0.56 $1,120.00 Per Diem and Lodging, per person per day 22 $140.00 $3,080.00 Subcontractors Triple R Mitigation 1 $24,000.00 $24,000.00 Vacuum meter, per day 20 $25.00 $500.00 TetraTech Subcontractor Markup (10%)$2,450.00 Direct Costs Subtotal $26,950.00 Task 200 Mitigation System Modifications Total $47,030.00 Task 300 Response to Requests from Homeowners Project Manager/Senior Hydrogeologist, per hour 32 $180.00 $5,760.00 Assistant Project Manager/Hydrogeologist, per hour 20 $100.00 $2,000.00 Principal Engineer, per hour 16 $275.00 $4,400.00 Environmental Scientist, per hour 8 $100.00 $800.00 Administrative Personnel, per hour 8 $70.00 $560.00 Labor Subtotal $13,520.00 DIRECT COSTS Tetra Tech Vehicle Mileage, per mile 400.00 $0.56 $224.00 Photocopies, estimate 50 $0.10 $5.00 Direct Costs Subtotal $229.00 Task 300 Response to Requests from Homeowners Total $13,749.00 Task 600 Project Management and Response to City Requests For Information Project Manager/Senior Hydrogeologist, per hour 36 $180.00 $6,480.00 Assistant Project Manager/Hydrogeologist, per hour 20 $100.00 $2,000.00 Environmental Scientist, per hour 8 $100.00 $800.00 Administrative Personnel, per hour 30 $70.00 $2,100.00 Labor Subtotal $11,380.00 DIRECT COSTS Tetra Tech Vehicle Mileage, per mile 400.00 $0.60 $240.00 Photocopies, estimate 200 $0.10 $20.00 Direct Costs Subtotal $260.00 Task 600 Project Management and Response to City Requests Total $11,640.00 TOTAL OF ALL TASKS $72,419.00 Tetra Tech 147