A communication transmitted from Louis A. DePasquale, City Manager, relative to Awaiting Report Item Numbers 18-11 and 18-12, regarding the Cambridge Crossing sewer main on Gore Street

City of Cambridge Department of Public Works Owen O'Riordan, Commissioner 147 Hampshire Street Cambridge, MA 02139 theworks@cambridgema.gov Voice: [phone removed] TDD: [phone removed] September 24, 2018 To: Louis DePasquale City Manager From: Katherine F. Watkins, City Engineer Re: Awaiting Reports 18-11 and 18-12, dated January 29, 2018 Gore Street In response to the council orders regarding the Cambridge Crossing sewer main on Gore Street, staff report the following: GORE STREET SEWER CONSTRUCTION UPDATE: Construction of a new city sewer main on Gore Street between Monsignor O’Brien Highway and Medford Street in Somerville commenced in spring 2018. Construction started in Somerville and is progressing to the east into Cambridge. The sewer installation is complete to almost Lambert Street. Work will continue to the east towards Monsignor O’Brien Highway this winter, as weather permits. The connection to the MWRA’s regional wastewater system in Somerville is expected to occur in 2019 and the sewer main construction is expected to continue into the 2019 construction season. This past spring, Eversource began replacing the over 100 year old gas main on Gore Street. Gas main replacement started near Monsignor O'Brien Highway and is proceeding west down Gore Street towards the Somerville city line. OPEN CUT CONSTRUCTION VS. TRENCHLESS TECHNOLOGY: The new sewer main is approximately 8 to 15 feet deep and is being constructed using typical open cut construction methods. Trenchless construction was proposed in the initial design, but was determined to be more disruptive to the community. While trenchless construction reduces the length of the excavation, significant excavation is still required. Relatively large access pits, called launching and receiving pits are placed at either end of construction zones where pipes will be installed. These pits are needed for the equipment and materials used in the trenchless process. Trenchless construction on Gore Street would have required two to three sets of access pits ranging in size from 8 to 10 feet wide by 15 to 25 feet long and depths of over 15 feet. The size of these access pits would present significant challenges on Gore Street due to the number of existing subsurface utilities and would be disruptive to the neighborhood. Laydown areas for the launching pits for the long lengths of fused pipe to be installed would have required significant removal of on-street parking. Sewer manholes, which are required for operation and maintenance, are required approximately every 300 feet. These manholes would need to be constructed using open cut excavation and would be 15 to 30 deep.

To reduce the depth of the construction, Divco West modified the design to include a sewer pumping station at Cambridge Crossing, which allows the sewer main to be installed at a higher elevation; reducing the excavation depths to 8 to 15 feet which is more typical for sewer construction and can proceed using the traditional open cut excavation method. CONSTRUCTION IMPACTS: The DPW has been working with DivcoWest to coordinate design and construction activities and reduce impacts to the community. • DivcoWest engaged with a construction mitigation firm, CSL Consulting, to manage construction notifications and updates, and to respond to concerns. CSL Consulting has set up a project web site with updates and contact information https://cxconstruction.info/ Residents can sign up for project updates through the web site. • DivcoWest and DPW co-hosted a public meeting in September 2017 to review the project and construction impacts; and discuss mitigation efforts. • Resident parking has been a key concern for Gore Street residents. The City has reduced the fees for monthly parking in the City’s First Street Garage for residents impacted by the construction and DivcoWest has committed to paying the fees. The information below explains how to sign up for the parking and has been distributed to residents. o The City is extending the wintertime $50 per month parking in the City’s First Garage to year-round for residents of Gore Street. DivcoWest will pay the $50 monthly charge for residents of Gore Street, so monthly passes in the City’s First Street Garage will be free of charge to Gore Street residents impacted by the sewer construction. Please contact [email removed] or by phone at [phone removed] to discuss parking options during construction. • DivcoWest has worked closely with the City’s Inspectional Services Department to identify any areas with rodent activity, coordinated with local businesses to improve existing rodent control plans and baited sewers in the Gore Street area. Proactive rodent management will continue throughout construction. • DivcoWest has offered preconstruction surveys to all properties on Gore Street. The notification process started in mid-January and all properties identified for preconstruction surveys were notified by mid-February. • DivcoWest held a meeting in the spring, 2018 to update impact residents on their construction efforts. • As part of the water main replacement, any lead water services will be replaced from the water main to the meter, at no cost to the property owner. • The design and construction of the surface reconstruction (paving, sidewalk, street trees, etc.) will be paid for by DivcoWest, but managed by the City. The kick-off community meeting for the surface design was held on June 19th and the second community meeting will be held on November 1st from 7:00 – 8:30 pm at Millers River, 15 Lambert Street.