Flood Mitigation Culvert

Culvert

Diagram of proposed culvert and floodway in relation to existing culverts

 

History of Flooding in Winchester

The low-lying areas adjacent to the Aberjona River in Winchester have been subject to flooding throughout history. The flooding has been exacerbated by an increase in storm water flows resulting from development both upstream and within Winchester over the past 40 years. The river’s 53-square mile watershed includes upstream areas of Woburn, Reading, Stoneham, and Burlington.

Residents of the Town feel the impact of flooding in two ways. First, they experience inconvenience and expense when their homes or businesses are flooded, causing property damage and resulting in time and cost for clean-up and repair.  Flooding has caused approximately $25M in property damage between 1996 and 2010, per the US Army Corps of Engineers.  (See 2010 FEIR.)  Second, owners of properties that are within the 100-year floodplain must purchase flood insurance.

After years of study, with assistance from professional consultants and input from citizens and Town committees, the Town undertook the process of designing, permitting and executing a Flood Mitigation Program (FMP).  The goal of this project was “to minimize economic losses from damaging floods by eliminating constrictions and undertaking projects to improve flow and capacity.”  The Town first filed an ENF (Environmental Notification Form) under the Massachusetts Environmental Policy Act (MEPA) in 2003 for a series of proposed flood mitigation projects, followed by Draft and Supplemental Draft Environmental Impact Reports, in 2006 and 2007 respectively.  A certificate was issued in 2007 for fourteen projects — ten within Winchester and four in neighboring towns.  In subsequent years, the proposal was refined through more filings by the Town and regulatory review by the Commonwealth, with input from a variety of regulatory agencies (such as DCR, the MWRA, the Massachusetts Historical Commission, etc.) and both upstream and downstream communities. In 2010, a Final Environmental Impact Report was submitted that listed nine projects – six within Winchester and three in neighboring communities.  On April 2, 2010, the Massachusetts Secretary of the Executive Office of Energy and Environmental Affairs issued a Certificate which allowed the Town to move into the detailed design and construction phases for the respective projects.  Each project within the FMP is critical to the success of the overall program, and some of the projects must be constructed in sequence to ensure that no new flood issues are created as a result of the execution of the projects. See April 27, 2015 Flood Mitigation Program Update to Town Meeting.

When the FMP is complete, the Town will experience lower levels of flooding, at a lesser frequency, from storm events.  See December 12, 2014 letter from VHB to BOS.  For low to moderate storm events, some impacts have already been reduced or eliminated. For more extreme flood events (100-year or greater storms), the impact will not be entirely eliminated, but will be reduced so that less property damage is experienced overall within the Town, particularly in the Town Center and north side of Town.  See December 12, 2014 letter from VHB to BOS.  The benefits accrue not only to private property, but to municipal buildings and infrastructure that have historically experienced flooding impacts.

In addition, upon completion of the FMP, the floodplain maps maintained by the Federal Emergency Management Agency (FEMA) can be amended to significantly reduce the 100-year floodplain area (which dictates which properties must be covered by flood insurance). The Town estimates that 145 out of 273 buildings currently within the 100-year floodplain will be removed, saving impacted residents annually on their insurance premiums.  See BOS Public Information Session March 16, 2015 and April 27, 2015 Flood Mitigation Update to Town Meeting.

Excellent Progress on FMP  The Town has successfully completed many of the projects in the FMP, and the anecdotal experience of recent flood events indicates that these projects are having a positive impact. However, the Town has not in recent years experienced the type of 100-year storm that was, in part, considered in the design of the program. In addition, because of the required sequencing of some of the projects, certain neighborhoods have yet to experience the benefits that will result from the projects that most directly target flooding in their region of Town.

Of the ten Winchester projects covered by the 2007 MEPA certificate, six have been completed, one is under way (the Mt. Vernon Street Bridge project is fully funded and will begin this summer), and three remain: Skillings Field, the Railroad Bridge Near Muraco, and the Swanton Street Bridge.  Funding has been secured for the two out-of-town-projects that are required prior to Skillings — the Medford Craddock Locks and Woburn Scalley Dam projects — and these are under way.  CLICK HERE for a detailed discussion of the status of the Flood Mitigation Program.

The Culvert Project and its Costs  Currently, the Aberjona River runs underneath Skillings Field through three 7-foot diameter pipe culverts. See photo of existing conditions HERE.  The proposed project will install a  7 foot x 15 foot box culvert – at a length of approximately 1300 feet — adjacent to the existing culverts to increase capacity in flood events, as well as create a surface floodway (on the western edge of Skillings) for overflow. Completion of the Skillings culvert will permit the Town to move forward with the two upstream projects to the north, the Swanton Street Bridge and the railroad bridge near Muraco School.

Preliminary design of this project is completed. If the project proceeds on the proposed schedule, the estimated cost for final design, permitting and construction is $7.45 million. (This compares to a cost of $7.9 million if conducted on a stand-alone basis.) A significant cost driver is the fact that the culvert must be supported with piles due to a 40-foot layer of peat underlying the area.

This project is the most expensive of all of the flood mitigation projects within the program, and is the only one for which the Board of Selectmen has proposed a debt exclusion override. While the tax impact will depend on lending terms at the time of borrowing (anticipated to be Spring of 2016), it is likely that the term of the bond would be 30 years, with an annual tax impact of approximately $64 for a home of average value ($872,100).[1] More information regarding the estimated tax impact is available HERE.

Document

[1] This estimate is for illustrative purposes only. The actual tax impact will depend on a variety of factors such as borrowing terms and time of borrowing.

Advertisements