ARLINGTON RESERVOIR DAM
SUMMARY OF DAM INSPECTION/EVALUATION REPORT
Date of Inspection: June 25, 1998
By: Hydraulic & Water Resources Engineers for DEM Office of Dam
General Notes: Assessment of Dam was based on the general conditions
and available data and visual inspections. The inspection was required
because a previous report in 1987 by Camp Dresser and McKee, Inc. reported
that there were serious structural, and/or hydraulic and/or emergency action
Findings from visual inspections (at time of inspection the water
elevation was 158.0 MSL (mean sea level) or 4 feet below the top of the
Summary of Recommendations
Evidence of extensive seepage and rust stained wet areas were observed
along the downstream toe in the area right of the emergency spillway. Wet
areas were also present along the downstream toe to the left of the spillway
where the Mill Brook flows adjacent to the toe of slope.
Spalling and mortared joints and missing stones were observed in the emergency
spillway training walls and outlet channel. There is erosion of the embankment
at its contact with the left training wall.
A crack and spalled area on the left concrete sidewall of the principal
gated spillway was found. There is a 4-inch diameter hole in the tainter
Riprap was absent and localized erosion from wave action was evident along
the upstream slope of the dam.
It is unknown whether or not the low-level outlet is operational.
Trees and debris are blocking the spillway outlet.
Heavy tree and brush growth make it difficult to monitor the condition
of the dam and to observe sinkholes, cracks, slides or animal burrows on
the upstream slope of the dam.
Estimated cost to complete work: $188,000 to $270,000
Implement a regular inspection program to monitor any changes in the condition
of the dam.
Remove trees and brush on the slopes of the earth embankment. Fill stumpholes
with compacted granular fill on downstream slope and compacted impervious
fill on the upstream slope.
Remove trees, brush and debris and repoint the spalled mortared joints
in the emergency spillway channel.
Provide riprap slope protection on the upstream slope of the embankment
particularly where erosion of the shoreline has occurred.
Repair the spalled concrete and crack on the left sidewall of the spillway
General Description of the Arlington Reservoir Dam
The Arlington Reservoir Dam is an earth embankment With a minimum top
width of 20 ft. The dam impounds water from the Munroe Brook and has a
drainage area of 2.36 square miles. The reservoir was built in the late
1800's and used for water supply for the town. The spillway crest gate
was built from 1957 to 1958.
The Arlington Reservoir Dam is presently used for recreation and flood
control. The overall length of the dam embankment is 1770 feet and is located
between Lowell Street and the Boston and Maine Railroad tracks (Minuteman
Bikeway) at the Arlington and Lexington town lines. The dam is an intermediate
size dam. There is a housing development immediately downstream of the
dam and therefore the dam is classified as Class 1, (high) hazard dam.
The responsibility for operation and maintenance of the dam lies with the
Arlington Department of Public Works.
Crest Gate Spillway with concrete sidewalls and wingwalls is located 80'
to left of emergency spillway. Gate can be raised from elevations 153 MSL
to 159 MSL with its crest 3 feet from below the top of the dam. It is manually
operated. Overflow passes into a 60 inch diameter, 70 foot long concrete
pipe and then into the Mill Brook.
Emergency Spillway is a stone and mortar channel which is about 20 feet
wide and 3 feet deep. Overflow from this spillway also empties into Mill
Brook. A steel service bridge in general disrepair spans the spillway.
Low level outlet is located about 800 feet to the left of the crest gate
spillway. The low level outlet empties into a 12" pipe which then empties
into a 15" concrete storm drain which then empties into the Mill Brook.
An earthen embankment 1770' feet long which has a structural height from
the dam crest to the lowest downstream slope of approximately 14 feet (only
an estimate). The top of the embankment is 162 MSL. Top of the dam downstream
is 148 MSL. The maximum storage capacity is approximately 480 acre feet.
The reservoir has a surface area of 65 acres.
Previous studies and reported problems:
Crest gate of sluiceway is used to regulate the surface water elevation
of the reservoir from elevations 159 MSL to 153 MSL.
Low level outlet (~ 148 MSL is used to draw the reservoir even lower.
Proposed Scope of Services for town funded study:
1981 by ASEC Corporation and 1987 by Camp, Dresser and McKee, Inc.
Previous concerns from hydraulic/hydrologic data from both studies: distinct
potential for overtopping the dam and the spillway is capable of passing
not more than 48% of the Storm Design Flood (based on a 1/2 PMF storm event
(I think a 500 yr. storm)).
Inspect the conditions at the dam and identify two repair options and
a cost estimate for selected repair option. Perform a hydraulic and hydrologic
study to evaluate the spillway capacity of the dam. Neither an Emergency
Action Plan nor an Operation and Maintenance plan will be completed.
[ Home ] [ Up ]