MBTA Studying Groundwater By Back Bay Station

The following is a press release from the MBTA:

The MBTA is continuing its commitment to work collaboratively with various city agencies and is presently working with a design team of engineering consultants to advance groundwater studies in the area south of MBTA’s Back Bay Station.  The design team is led by GZA GeoEnvironmental, Inc. and also includes Parsons Brinckerhoff, C&C Consulting Engineers, Green International Affiliates, Inc. and several consultants.  The ongoing studies focus on evaluating the cause of locally depressed groundwater levels and developing methods to maintain groundwater levels and preserve the integrity of timber pile foundations that support many of the buildings and structures in this area. 

At present, there are a total of five recharge wells located on Cazenove Street, St. Charles Street, and Berkeley Street that pump groundwater from the city water system into the ground.  These recharge wells have been in operation since 2003 as part of a Short-Term Groundwater Action Plan developed by the Boston Water & Sewer Commission, the MBTA, and other city agencies to address community concerns. 

 While the present groundwater recharge system is operating, the MBTA and their design team are developing a more permanent groundwater recharge solution (i.e. Long-Term Groundwater Action Plan) that will consider:

• The effectiveness and efficiency of the existing recharge system relative to maintaining the water table at elevation 5.0 (Boston City Base datum),
• The use of storm water to elevate the depressed water levels, rather than the city’s drinking water, and
• Constructing impermeable vertical barriers to reduce the volume of water required for a long-term recharge system.

The overall approach involves the development of a numerical groundwater model to simulate groundwater flow patterns and the elevation of the water table for a variety of potential recharge schemes. Data collection in support of model development is ongoing, which includes: monitoring changes in groundwater elevations due to precipitation, artificial recharge, and on-going pumping; installing monitoring wells to supplement the relatively large number of observation wells that were installed and are being regularly monitored as part of the overall Boston Groundwater Trust initiative; performing a pumping test using existing storm water management structures; and shutting down the existing recharge wells for about one month to assess the effectiveness of the existing recharge system.  It is anticipated that shut-down of the recharge wells will commence during the month of July. 

The ongoing studies, including the temporary shut-down and restart of the recharge wells, are not anticipated to disrupt residents in the area nor have adverse affects on their structures.  Barring unanticipated conditions, the MBTA and their consultant anticipate that the findings of the groundwater study will be completed and presented to interested parties in the late fall 2012/early winter 2013. For further information about groundwater study in the Back Bay area, please visit:  http://www.mbta.com/about_the_mbta/t_projects/default.asp?id=19604