Transcript October Storm Flows - Blackstone River Coalition

October Storm Flows
City of Worcester DPW & Parks
Department, Sewer Operations
Division January 26,2006
Today's Discussion
• We are going to talk about Worcester Sewer
System, and how it is interconnected to our local
waterways.
• We will review some of the cities large scale
Flood Control systems
• What DPW does to control street and limit
flooding
• We will talk about the heavy October Rains and
some of Worcesters geographic characteristics
• What effect did the storm have on Worcester
Basic Statistics on
Worcester’s System
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371 miles of sanitary sewer
340 miles of surface sewers
56 miles of combined sewers
27,000 manholes
15,000 + catch basins
329 outfalls
93 major outfalls
31 pump stations
Interceptor
Sewers
City of Worcester
-Topographic Layout
of the City
-Interceptor Sewers
Shown In Red
Worcester,
Interconnected
Waterways; Culverted
Waterways on this map
were constructed for Flood
Control, Development ,
and the overall protection
of the city. Culverting of
waterways and related
improvements go back
over 80 years. The
waterways include; Beaver
Brook, Mill Brook
Fitzgerald Brook and
Kettle Brook Tributaries.
Worcester, Large Scale
Flood Control; The first
major flood control
construction was the
Beaver Brook Channel
around 1914, followed
ditching culverting streams
in Tatnuck Brook, Broad
Meadow Brook, Fitzgerald
Brook, Kettle Brook, and
Coal Mine Brook in the
1930’s . Beaver Brook was
also culverted extensively
through the 1940’s.
Combined Sewer
Area
City of Worcester
-Topographic Layout of
the City
-Combined Sewer Area
Shaded
Worcester
Combined Sewer System
Major Flood Control Projects
• The Worcester Diversion,1955 effectively shuts
off Kettle Brook form entering the city through a
16 foot diameter tunnel that runs under Pakachoag
Hill in Auburn Massachusetts.
• The Chandler Hill Flood Control Project, 1955,
which takes flows from East Park and includes a
96 inch pipe which runs down most of
Shrewsbury Street to carry flood waters.
Major Flood Control Projects
(continued)
• Through the mid to late sixties three ponds were
eliminated in the West Boylston Street, Gold Star
Blvd. Area. Twin Box Culverts eleven by seven
feet were installed to carry flows from the Weasel
Brook area and Indian Lake to Salisbury Pond.
• Around this time the Ararat Brook Flood Control
project was also complete north of Indian Lake
Major Flood Control Projects
(continued)
• Through the seventies and eighties storm flows
were removed from the old Mill Brook Conduit,
which is basically the covered over Blackstone
Canal, by constructing a series of large concrete
culverts that take flows from Salisbury Pond to the
Blackstone River. There are now two underground
rivers running through the center of the city, one
for storm flows and one combined sewer flows.
Major Flood Control Projects
(continued)
• There are many more major drainage
programs that have been completed to
mitigate localized flooding. Most recently
the Mill Brook sewer was extended to
outfall further down stream to reduce
flooding in the Green Island Area.
Storm Drain System Maintenance
• We clean all city catch basins over a two
year period, but if a basin is not working we
will make every effort to get that basin to
work.
• We clean flush and TV inspect many
portions of the stormwater system daily.
• We sweep streets to keep sand, leaves and
debris from blocking city storm drains.
Storm Drain System Maintenance
(continued)
• The Storm drainage systems in the city are
monitored in dry and wet weather hoping to
find problems before they happen.
• We have over 50 choke points or stream
crossings that we check bi-monthly in dry
and wet weather in hopes of limiting the
chances of flooding.
The October Storm
October Storm Flows
14
12
Nine days of
rain
Inches of Rain
10
8
daily
total
6
4
2
0
0
2
4
6
8
10
Days
12
14
16
18
The October Storm
October Storm Flows
14
12
Over 12
inches of rain
Inches of Rain
10
8
daily
total
6
4
2
0
0
2
4
6
8
10
Days
12
14
16
18
DPW Received Over 200
Complaints
• 17 % were street flooding
• 11 % were blown off or missing man hole
covers
• 36 % were sewer backing up into house
• 36 % were water backing up into cellar
We estimate there were many more problem
areas that simply were not reported.
Inflow & Infiltration II
• The nine days of rain coupled with the
heavy rain, of October 15,2005 caused
extreme snow melt like conditions in the
sanitary sewer system. High ground water
conditions surcharged the soil and
consequentially the sewer system. The rain
and ground water conditions filled the
sewer system with excess ground water, just
like a leaky basement.
Inflow & Infiltration II
(continued)
• The excess storm flow that entered the
sanitary sewer system, blew off manhole
covers, backed up into peoples homes,
caused sanitary sewer overflows (SSOs),
and Pump Stations to by-pass.
Where are we headed
• Continuing the I/I program development
and implementation.
• Development of the cities backflow
prevention program.
• Continue the cities storm drain system
maintenance
Questions