Section 4 - Environmental Inventory and Analysis
A - Geology, Soils & Topography
GEOLOGY
Plymouth County's superficial geological map identifies three basic geological
formations in East Bridgewater.
1.
Lake Bottom Deposits - Formations of sand, silt and clay glacial lake bottom
sediments overlain locally by sand and gravel are predominantly found in the
southern half of town.
2.
Ground Moraine - This the formation includes loose, sandy till, dense clay fill and
drumlins. This dominates the northern half of East Bridgewater which consists
mostly of till overlaying bedrock.
3.
Stratified Drift - Also found in the northern half of Town, stratified drift includes
water borne deposits ranging from coarse gravels and sands, to silt and clay.
SOILS
The soil information was obtained from a previous "Open Space Report"
compiled by the Old Colony Planning Council dated December 15, 1987. The four major
groups are listed and described below accompanied by a map which shows the location of
each group.
Merrimac - Hinckley - Windsor-Deerfield Association
This association occupies 39% of the Town of East Bridgewater. It consists of
droughty and moderately well drained sandy and gravely soils on gentle to steep slopes.
Much of the general soil area is used for residential purposes, but other parts are forested.
Merrimac soils occupy about 35% of the association, Hinckley soils occupy about 25%,
Windsor occupy about 15% and Deerfield soils occupy about 10%.
Scarboro - Muck - Saco - Brockton Association
About 37% of East Bridgewater soil is of this association which consists of very
poorly drained mineral and organic soils on low, nearly level terrain. The general area is
mostly either red maples woodlands or marshy vegetation such as reeds and cattails.
Scarboro soils occupy about 35% of the association, while Muck soils occupy about 25%,
Saco soils occupy about 15% and Brockton soils occupy about 12%.
Section 4 - Environmental Inventory and Analysis
A - Geology, Soils & Topography
SOILS (continued)
Essex - Scituate Association
These soils encompass approximately 21% of the Town. They consist of welldrained soils with a dense underlying fragipan developed in compact glacial till on level
to gently sloping terrain. Most of this association is either left to forest or used for open
farming. Some tracts however, have been developed for residential use. Essex soils
occupy about 45% of this area while Scituate soils occupy about 40% of the area.
Belgrade - Ninigret silty substratum Associate
Only 3% of the Town is subject to this moderately well drained silty and sandy
soil on gentle to moderate slopes. Some of this association has been developed for
residential use, however, most of it is forested. Belgrade soils occupy about 45% while
Ninigret soils occupy about 40%.
TOPOGRAPHY
The topography of East Bridgewater consists mostly of gentle rolling terrain.
Elevations range from 40 feet to 140 feet above mean sea level. Other features include
irregular knolly hills, level terraces with steep escarpments, and low areas found along
streams, drainage ways and in swamps.
There is one major hill in the northwestern part of Town. It is located off
Highland Street. The elevation of this hill reaches about 145 feet above sea level.
Section 4 - Environmental Inventory and Analysis
A - Geology, Soils & Topography (continued)
Soil patterns constrain or influence development by affecting the feasibility of onsite sewage disposal systems. Similarly, areas of wetlands, flood plains, or steep slopes
can limit the practicality or safety of development.
The 1988 Master Plan reported that the effects of soil limitation, wetlands, and
flood plains on development suggests that large lot areas with severe septic limitation
will accommodate about 70% as many lots as otherwise would be allowed, and that
flood plain and wetland areas will accommodate about 50% as many lots as otherwise
would be allowed.
When compared to the soil maps, development has traditionally taken place in
areas where the soil limitations are less severe. The older parts of Town such as the
center and Elmwood were developed in the less severe soils. Most of the older roads
accommodating the Form A development were Central, Plymouth, Union, Belmont,
Bridge and Summer Streets. These streets tend to run through less restrictive soils.
Developers will continue to seek the most useable sites. However, there is a
scarcity of land without sever soil limitations. Thus developers will seek to use more
marginal lands as those parcels are made available for sale.
The major undeveloped areas are located back from existing road systems. Much
of these areas have wetlands, streams and rivers traversing them. Even so, there are
upland sites available for development within these natural protected features.
The 1988 Master Plan identified ten large undeveloped areas of East Bridgewater
that probable residential development will occur. The calculations used in the analysis of
major undeveloped areas assumes that 10% of the land would be lost to construction of
the roads and drainage. Also, it was assumed that only 50% of the total acreage in the
flood plain could be used. Lastly, it assumed 45,000 square foot lot sizes for the Water
Protection District and that only 70% of the land in the septically restrictive (wetness and
soil limitations) area would be buildable.
Section 4 - Environmental Inventory and Analysis
A - Geology, Soils & Topography (continued)
The 1988 Master Plan determined that there is approximately 5,504 acres of
undeveloped land which did not include agricultural land which would be available for
future development. Taking into consideration the wetland, flood plain and severe soil
limitations located in these undeveloped areas, the 1988 Master Plan predicts a potential
of 4,560 additional housing units. With three people per unit, this could mean an added
population of 13,680 to the current 12,442 residents of the Town or a total of 26, 122.
The areas with the potential for increased residential growth are the northeast and
southeast portions of Town with a third area bounded by Washington, Plymouth and
Central Streets having the biggest potential for growth. Other areas that are predicted to
grow are the southwest area, an area north of Highland Street and an area west of South
Street.
If the rate of growth continues at a little over 10% per decade, the Town could see
itself reaching full build-out by the year 2067 or only 70 years from now. In the
meantime, the predicted growth of Southeastern Massachusetts and the expansion of the
transportation infrastructure could speed this build-out sooner. Also, if more of the
agricultural land is lost to developers that was considered in the 1988 Master Plan, the
total new units could rise even quicker. No matter when it occurs, the Town’s character
will have changes dramatically unless proper planning is made a priority by local
officials, politicians and town residents.