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In 2007, BSI Engineering, Inc. was awarded the subsurface utility
Engineering portion of the South Boston Reserved Channel Contract
for the Boston Water & Sewer Commission reserved channel combined
sewer separation project. The main goal of the project was the
separation, to the extent practical, of the existing combined sewer
system tributary to the BOS 076, 078, 079, 080 outfalls in the
Reserved Channel in an effort to eliminate or significantly reduce
the number of discharges of combined sewage to the channel. The main
objective was to meet the State’s Water Quality Standard for the
Reserved Channel which is SB/CSO. This classification provides for
protection of aquatic life and primary and secondary contact
recreation and accounts for the fact that there will be periodic wet
weather discharges from the combined sewer system that will create
short term impairment of uses. A secondary objective is to minimize
the construction-period and impacts on local residents.
Using 2003 conditions as a baseline, the MWRA estimated that sewer
separation can reduce the number of annual CSO discharges to the
Reserved Channel from 37 to 3 per year, and reduce the annual volume
of CSO from 41.3 to 1.5 million gallons. As a result, the targeted
CSO condition to meet SB/CSO water quality standards discharge was
set at three activations per year and less than 1.5 million gallons
of overflow per year.
In order for engineers to complete the project in a cost effective
manner, it was necessary to determine accurate locations and depths
of existing utilities. As is often the case in cities the size and
age of Boston, existing utilities record information was not
reliable. Using the latest utility detection equipment and methods,
BSIE performed quality level B electronic designation services per
CI/ASCE 38-02 and survey located all designation results to create a
composite utility plan.
Upon review of BSIE’s composite utility plan; specific locations
were determined to be of critical importance. Vacuum excavation was
utilized to safely expose the subsurface utilities in these
locations followed by survey locating the test hole results. With
this information BSIE created utility profiles with actual depths to
utilities vs. assuming standard depths for existing facilities based
on record information which can lead to costly change orders during
the construction process. BSIE then compiled both the quality level
B, C, and D information with the quality level A information to
create a full composite utility plan thus fulfilling all the
information requirements of the designer. This contract is ongoing
for the next 5-7 years.
All of the subsurface utility engineering services provided to the
Boston Water & Sewer Commission follow the guidelines of the CI/ASCE
38-02 “Standard guidelines for the collection and depiction of
subsurface utilities” of which BSIE’s principal, James F. Noone,
P.E. is a committee member.
Contact one of BSIE’s skilled and experienced engineers today to see
how your project can benefit from your relationship with BSI
Engineering.
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