University Avenue
" A poster child of what not to do."
- Hydrologist who informally reviewed the stormwater system, well field, and data from University Ave in Westwood
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Stormwater runoff associated with development along University Avenue in Westwood is affecting groundwater and drinking water wells in the Whitelodge Well Field, which serves both Dedham and Westwood.
Available data shows rising salt concentrations in these wells over time – patterns that do not align with the long-standing explanation that highway expansion alone is responsible. Understanding how groundwater and stormwater systems interact is essential to evaluating potential risks, long-term costs, and options for protecting local water resources.
Click here to view the analysis presented to the Dedham Select Board
The Whitelodge Well Field, located primarily in Westwood, supplies a significant portion of Dedham’s drinking water. Available data show a clear increase in salt accumulation within the Whitelodge wells over time. This issue was identified by the Dedham-Westwood Water District (DWWD) in 2004, with a notably sharper rise in salt levels beginning in late 2014.
While salt is not regulated as a primary drinking water contaminant at the federal or state level, Massachusetts requires monitoring and reporting of sodium and chloride levels. These requirements are intended to ensure residents – especially those with health conditions affected by salt intake – are informed about water quality. In addition, stormwater from the University Avenue area in Westwood is discharged into Fowl Meadow in Dedham, which is designated as an Area of Critical Environmental Concern (ACEC) because of its importance to drinking water protection and sensitive ecosystems.
Public explanations have attributed the accelerated salt accumulation to the state’s “Add-a-Lane” expansion of Interstate 95. However, when local topography and the layout of the Whitelodge Well Field are considered, this explanation raises important questions. Four of the five wells are located uphill (up-gradient) from the highway, meaning groundwater would have to flow uphill for the highway to be the primary source of contamination.
SodiumGraph.pngThis publicly shared graph aggregates salt data from all five wells (Click on graphic to expand)
While useful at a high level, combining the data can mask important differences among individual wells, making it harder to pinpoint specific sources and timing of increased salt inputs.
whitelodge salt graph Screenshot.pngSalt accumulation by well timeline (Click on graphic to expand)
The commonly cited explanation that attributes rising salt levels to the I-95 “Add-a-Lane” project can be evaluated by looking at salt accumulation trends at each Whitelodge well over time. Because the five wells are roughly aligned in a straight line and spread over approximately one mile, this explanation should demonstrate a clear pattern: salt concentrations should decrease as distance from the highway increases.
The data do not show this pattern. When salt levels are examined well by well, no consistent decrease with distance from I-95 is observed. In fact, the well farthest from the highway shows some of the highest salt accumulation of all five. This finding is not consistent with the "Add-A-Lane" project being the primary source of salt and suggests that other sources or pathways may be contributing to groundwater contamination.
Analyzing salt levels on a well-by-well basis indicates that an additional source of salt is affecting the Whitelodge Well Field. To further investigate, the area surrounding the wells along University Avenue was reviewed using historical imagery in Google Earth.
That review shows that the I-95 “Add-a-Lane” project in Westwood was largely completed by around 2010 – several years before the period when accelerated salt accumulation began to appear in the individual wells. Based on this timing, the highway expansion alone does not fully explain the observed increase in salt levels.
(Click on graphic to expand)
2014- Univ-Ave-GoogleEarth_Image.jpgDuring the same period as the 'Add-a-Lane' project, a major new stormwater management system was also constructed to serve development along University Avenue. When the timelines of both projects are compared, the data do not support the highway expansion as the primary driver of salt accumulation in the Whitelodge Well Field.
By contrast, the timing of the University Avenue stormwater system aligns with the observed increases in salt levels, but this system has been completely left out of public explanations or data analyses to date.
Expert feedback from the Dedham Water Resource Advisory Committee emphasized the importance of studying subsurface conditions, including soil conductivity and geology. In response, additional research was conducted and supported the conclusion that the 'Add-a-Lane' project was not the primary cause of salt accumulation.
Engineering data show that the underground topography acts like a funnel, drawing groundwater from the surrounding area toward the center of University Avenue. This effect is amplified by soil conditions that allow water—and dissolved salt—to move easily through the ground around the wells.
Although stormwater from new development is discharged at the edges of the well field, it is not shed from the well field. Instead, underground topography and highly porous soils act as a conduit, directing that water back toward the center of the well field.
This process is intensified by the wells themselves. The massive volume of water pumped to supply Dedham and Westwood creates a vacuum effect—or 'cones of influence'—that pulls salt-laden runoff from the perimeter directly into our drinking water supply.
When the stormwater system built to support new development is overlaid with the ground water features, the picture becomes clear:
Univ. Ave Stormwater system groundwater feature relationships.png(Click on graphic to expand)
Coloration indicates areas of varying levels of hydrologic conductivity. The areas most conducive to groundwater movement are indicated by varying shades of blue and are located:
directly on top of the well field and underlying aquifer, and
at the locations of the vast majority of stormwater outflows at University Ave.
White oval contours represent groundwater topography, indicating likely flow direction. These contours:
show a pronounced groundwater depression centered under Well #1 at the DWWD plant, and
suggest that groundwater is being drawn towards the center of University Ave. from the perimeters where the stormwater outflows are releasing storm run-off into the most hydrologically conductive ground.
Gold triangles are stormwater outflows
The stormwater management system northeast of the University Avenue campus is fundamentally flawed. First, while the retention pond is supposed to let contaminants settle out of the water, the installed fountain actively circulates the pond, re-mixing those pollutants back into the water.
Second, this system is connected to the state's I-95 stormwater drainage network, which discharges directly into the Fowl Meadow wetlands. This is particularly concerning because Fowl Meadow contains the district's most productive well and was designated an Area of Critical Environmental Concern (ACEC) in 1992 specifically to protect the very drinking water now being threatened.
Univ. Ave Stormwater system into Fowl Meadow.pngNortheast stormwater outflows and groudwater flow near the Whitelodge Well Field (Click on graphic to expand)
Red arrows indicate direction of stormwater flow.
Gold triangles are stormwater outflows
The stormwater management system southwest of the University Avenue campus discharges stormwater into a large open ditch, where it enters soils identified as being highly conductive to groundwater movement, up-gradient, and in close proximity to wells #3 and #4.
Univ. Ave Stormwater system west into Well Field.pngSouthwest stormwater outflows and groudwater flow near the Whitelodge Well Field (Click on graphic to expand)
Gold triangles mark stormwater outflow locations. Most University Ave outflows are are positioned uphill (up-gradient) and in close proximity to the wells.
Color shading shows areas of varying hydrologic conductivity. The areas most conducive to groundwater movement are indicated by varying shades of blue and are located:
directly on top of the well field and underlying aquifer
beneath the vast majority of stormwater outflows at University Ave.
White oval contours represent groundwater elevation and likely flow direction. These contours:
show a broad groundwater depression centered under Well #1 at the DWWD facility
suggest groundwater is being drawn towards the center of University Avenue from the perimeters where the stormwater outflows are releasing storm run-off into the most hydrologically conductive ground.
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