PRACTICES

BEAR BROOK INTERCEPTOR
REHABILITATION: SACO, ME
Two Trenchless Technologies Utilized to Rehabilitate
Interceptor in Environmentally Sensitive Area
By: Peter Goodwin, Ted Berry Company
Bear Brook pipe burst lengths ranged from 39 LF to over 450 LF
The City of Saco, Maine encompasses
53 square miles of prime real estate
along Maine’s Southern coastline
and is located approximately 14 miles south
of the city of Portland, Maine. Saco is a destination
for residents and visitors alike due
to its geographic location between Portland
and Boston, along with its proximity to the
Maine Turnpike, US Route 1, and the Amtrak
Downeaster rail station.
In the 1800’s, Saco was a center for
lumbering with timber from Western Maine
transported down the Saco River to sawmills
that produced much of the lumber for shipbuilding
in that era. In the mid 1800’s energy
from the Saco River was harnessed on Factory
Island where Saco Iron Works and Saco
Manufacturing Company produced iron
products and fine linens. Textile manufacturing
was a significant industry in Saco and
neighboring Biddeford, Maine for over 175
years with the last mill closing in 2009.
Based on the 2010 US Census, Saco currently
has approximately 18,500 residents.
Like many New England manufacturing
communities, the initial sewer system was a
combined sewer system conveying rainwater
runoff, domestic wastewater, and industrial
wastewater in the same pipe direct discharging
into the Saco River. In 1971, Saco constructed
its first wastewater treatment facility
on Front Street along the Saco River, which
was upgraded in 1988 to its current design
capacity of 4.2 MGD. Since 1995, the City has
been completing an aggressive sewer separation
program to reduce nine CSO discharges
down to four currently. The treatment facility
is now known as the Saco Water Resource
Recovery Facility (WRRF).
The collection system consists of 69 miles
of gravity sewer and interceptor, 20 miles
of pressure pipe and 31 pump stations. The
gravity sewer system has a wide variety of
pipe material including reinforced concrete,
brick, PVC, cast iron, clay, ductile iron,
HDPE, fiberglass, and asbestos cement. The
Saco WRRF treats an average daily flow of
approximately 2.5 MGD from the 4,700
customer accounts. City staff have indicated
that seasonal wet weather flow can increase
to over 12 MGD at the facility.
Based on a review of pump station flow
data, WRRF staff identified the Bear Brook
sewershed as an area with significant rainfall
induced infiltration/inflow (I/I). The sewershed
includes 109,000 LF of 8-inch to 24-inch
gravity sewers. The Bear Brook Interceptor
is located along a cross-country route
immediately adjacent to Bear Brook with
pipe size ranging from 15-inch to 24-inch
asbestos cement. Wet weather flows at the
pump station were found to peak at 4-6 times
average the dry weather flows which could
lead to activation of the WRRF wet weather
treatment facility on Front Street.
In 2014, the City retained ADS Environmental
Services to perform a two tier micrometering
study of the Bear Brook sewershed.
From early March 2014, eight storm events of
varying duration and intensity occurred and
were utilized to identify a significant source
of runoff where a storm water detention
pond was connected to the sewer. The micrometering
study also confirmed that the Bear
Brook Interceptor was a significant source of
groundwater infiltration.
The City WRRF staff and City Public
Works team evaluated rehabilitation alternatives
for the sewer segments identified in the
study. Located in a cross country easement
directly adjacent to Bear Brook, the Interceptor
has depths ranging from six feet to areas
over twelve feet. Due to the environmental
considerations of working alongside the
“…TED BERRY’S EXPERTISE IN TRENCHLESS
TECHNOLOGIES CAN SAVE THE COMMUNITY
SCARCE REHABILITATION MONIES. THE CITY
OF SACO COULD NOT BE HAPPIER WITH THE
OUTCOME OF THE PROJECT”
34 NASTT-NE NORTHEAST JOURNAL OF TRENCHLESS TECHNOLOGY PRACTICES 2016 | WWW.NASTT-NE.ORG