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HomeMy WebLinkAbout2022-08-15 Infrastructure Committee Minutes1 Infrastructure Committee Minutes August 15, 2022 ATTENDEES Councilors: Gretchen Shaefer, Dina Yacoubagha, Jonathan Sprague, Rick Fournier, Dan Tremble, Susan Hawes, Joseph Leonard Staff: John Theriault, Richard May AGENDA 1.Update: MS4 Permit Requirements – Implementation Process for LID (Low-Impact Development Ordinance Richard May informed the Committee the City would need to develop an ordinance for implementing a Low- Impact Development and is required to submit to DEP a model by September 1st for the new cycle of the stormwater compliance permit. Buy July 2024 the ordinance should be adopted. He further explained and there was discussion of the details of the Low-Impact Development. Vote: no vote necessary, informational only. 2.MDOT Agreement: WIN #026354.00, Kenduskeag Avenue & Griffin Road Traffic Safety Improvments John Theriault outlined the Order would authorize the City Manager to execute an agreement with Maine Department of Transportation for the Kenduskeag Avenue & Griffin Road Traffic Safety Intersection Improvements. The scope of the agreement includes the design, right-of-way, construction and construction inspection work for traffic safety improvements at the intersection of Griffin Road and Kenduskeag Avenue. The MPO program estimated cost is $265,859.00. Federal share of the project is $212,471.20 or 80%, State share is $26,558,90 or 10%, and the City's share is $26,558.90 or 10%. Vote: motion made and seconded, unanimous vote to move to Council. 3.Coal Tar Remediation Update Next Phase of Work by Burns & McDonnell Engineering Company, Inc. John Theriault provided the background and outline his following memo to the Committee: Dunnett’s Cove within the Penobscot River was exposed to coal tar contamination resulting from the operation of Bangor Gas Works, a manufactured gas plant in Bangor from 1850 to 1963. This gas plant was located on the property off of Main Street where the Shaw’s supermarket currently exists. Wastewater from the plant, containing coal and oil tar, was sent to the Davis Brook sewer and discharged to the Penobscot River at the Davis Brook outfall. In 2007, the City of Bangor entered into a Consent Decree with the Maine DEP to address this contamination. Burns & McDonnell have been working with the City of Bangor for over 20 years to address the coal tar contamination within the Penobscot River and meet the remediation goals as required by the Maine Department of Environmental Protection. The City is fortunate that Gene Mclinn, from Burns & McDonnell, has been involved with this project from the beginning. Much of the following summary is from previous reports prepared for the City by Burns & McDonnell. Data gathered at the site have revealed that variably weathered tars (coal tar and petroleum tar), in the form of non-aqueous phase liquids (NAPLs), and elevated concentrations of polycyclic aromatic hydrocarbons (PAHs) are present in sediment. The area of visible tar in sediment (including the sediment that historically generated tar sheens) is defined as the “Tar Deposit”. 2 The Tar Deposit is contained within Dunnett’s Cove and its immediate area, and there is no ongoing source adding fresh tar to the Tar Deposit. The Tar Deposit is approximately 11.4 acres in total area, comprising of three distinct zones (Figure 2): • Primary Active Zone (PAZ) – Area of liquid tar in sediment and active gas and tar migration to the surface at low tide, approximately 1.3 acres. • Secondary Active Zone (SAZ) –Area with elevated PAHs in sediment, gas with scattered thin sheen at water surface at low tide, about 2.0 acres. • Inactive Zone (IZ) – area with hardened tar deposits (like pavement) on river bottom having an area of about 8.0 acres. Prior to the City’s remediation efforts, tar blebs migrated from the sediment in the PAZ and SAZ in the presence of ebullition (gas bubbling), and formed tar sheens on the river’s surface. Based on field and laboratory measurements, over 99 percent of the observed tar migration was from the PAZ, less than 1 percent of the observed tar migration was from the SAZ, and no tar migration was observed in the IZ. A dredging and capping remedy for the PAZ was constructed in 2009. The PAZ remedy appears to have eliminated virtually all tar migration from this area. A capping remedy for the SAZ was constructed in 2017 and appears to have been successful in elimination of the “bathtub ring” (small band of sheen) that was observed at low tides within the SAZ. With successful remediation projects completed in the Primary Active Zone (PAZ) and in the majority of Secondary Active Zone (SAZ), the City must move onto evaluating and coming up with remediation options for a small sliver of area in the SAZ and in the Inactive Zone (IZ). The majority of the Inactive Zone (IZ) falls within the navigational channel of the Penobscot River. Early remediation plans called for a cap to be placed within the IZ. The Army Corp of Engineers has stated that they will not allow for any fill to be placed within the navigational channel which results in a conflict with the City’s original plans for remediation within the IZ. Burns & McDonnell have provided the City with a proposal for the next steps for this project. The scope of this proposal was based on a meeting in May of 2022 with staff from DEP, Gene Mc Linn, and John Theriault. The Proposal includes providing a summary of the past performance of the sediment caps at the PAZ and the SAZ as well as documented monitoring and studies within the Inactive Zone (IZ). A comprehensive summary will also be developed for the two previous Explanation of Significant Differences (ESD) Reports for the remediation efforts at the PAZ and the SAZ to explain how the constructed remediation varied from the original proposal outlined in the Consent Decree. Finally, a narrative for the ESD Report for the Inactive Zone will be developed for options to address the contamination remaining in the Inactive Zone. These options may consider an improvement project somewhere else on the river in Bangor, a monetary contribution to mitigate the remaining contamination, or that no additional remediation is needed. It should be noted that continued monitoring of the caps in the PAZ and SAZ will likely be a long term commitment from the City that Maine DEP will require. Burns & McDonnell’s fees for the discussed services is $98,000.00. With Burns & McDonnell’s long history with this project, the Engineering Department recommends awarding this work to them. Vote: Motion made and seconded, unanimous vote to move to Council. Meeting adjourned.