1-1 1. EXISTING WATER SYSTEM GIS MAPPING AND MODELING 1.1. General Background The Town of Milton’s water distribution system is supplied by the Massachusetts Wat er Resources Authority (MWRA) via the MWRA Southern Extra High (SEH) and Southern High (SH) water networks, see Fig. 1.1. The SEH service supplies water to the high pressure zone located in the southern portion of Town through one connection at MWRA Meter #55. According to the MWRA 2011-2013 water meter record information, the hydraulic grade line (HGL) at Meter #55 fluctuates between 375 and 396 feet, with an average of 385-feet (all elevations refer to USGS datum). There are three water storage tanks located within this zone; each with an overflow elevation of 375-feet. The high pressure zone also services a small number of Town of Canton residents through water mains in Hillside Street and Blue Hill Avenue. The SH service supplies water to the low pressure zone located in the northern portion of Town through two connections at MWRA Meters #27 and #107. According to the MWRA 2011-2013 water meter record information, the hydraulic grade line at Meter #27 fluctuates between 256-feet and 272-feet, with the average of 264-feet and Meter #107 fluctuates between 244-feet and 272-feet, with the average of 258-feet. There are no water storage tanks or pump stations located within the low pressure zone. 1.2. Collection, Review and Modification of Available Information The Town’s Geodatabase was reviewed and updated by BETA and Town personnel. The following adjustments were made in order to complete and streamline the data for use with the hydraulic model and the asset management program. Removed any unused or unnecessary fields, Added additional fields as required, Populated information required for hydraulic modeling including water main size, pipe material and year of pipe installation, Incorporated information from recent replacement/rehabilitation projects, Coded mains as either cement lined or unlined, Incorporated institutional knowledge relating to water main breakages and problem areas. Created a Town-wide water system network and Master Geodatabase for use on the project Upon completion of the above Geodatabase information, system connectivity issues were identified and resolved prior to creation of the hydraulic model. These issues included the following: Hydrants that did not have an accompanying hydrant lateral or hydrant gate valve were provided a hydrant lateral and where appropriate a gate valve. While the hydrant laterals are not necessary for water modeling purposes, it is helpful to display them as a background layer to indicate which water main a specific hydrant is connected to. Also, hydrants located at corners of intersections and on roads with multiple water mains can contribute to inaccuracies within the model. Hydrant valves that were shown in back of the hydrants or on the opposite side of the water main were reinserted in the correct location. Water main pipe segments were broken at junctions with other pipes and not at gate valves. Breaking the water main pipe segments at gate valves will increase the accuracy and usability of the water model. This will also increase the number of nodes/locations to check pressures
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1-1
1. EXISTING WATER SYSTEM GIS MAPPING AND MODELING
1.1. General Background
The Town of Milton’s water distribution system is supplied by the Massachusetts Water Resources
Authority (MWRA) via the MWRA Southern Extra High (SEH) and Southern High (SH) water
networks, see Fig. 1.1. The SEH service supplies water to the high pressure zone located in the
southern portion of Town through one connection at MWRA Meter #55. According to the MWRA
2011-2013 water meter record information, the hydraulic grade line (HGL) at Meter #55 fluctuates
between 375 and 396 feet, with an average of 385-feet (all elevations refer to USGS datum). There
are three water storage tanks located within this zone; each with an overflow elevation of 375-feet.
The high pressure zone also services a small number of Town of Canton residents through water
mains in Hillside Street and Blue Hill Avenue. The SH service supplies water to the low pressure
zone located in the northern portion of Town through two connections at MWRA Meters #27 and
#107. According to the MWRA 2011-2013 water meter record information, the hydraulic grade line
at Meter #27 fluctuates between 256-feet and 272-feet, with the average of 264-feet and Meter #107
fluctuates between 244-feet and 272-feet, with the average of 258-feet. There are no water storage
tanks or pump stations located within the low pressure zone.
1.2. Collection, Review and Modification of Available Information
The Town’s Geodatabase was reviewed and updated by BETA and Town personnel. The following
adjustments were made in order to complete and streamline the data for use with the hydraulic model
and the asset management program.
Removed any unused or unnecessary fields,
Added additional fields as required,
Populated information required for hydraulic modeling including water main size, pipe
material and year of pipe installation,
Incorporated information from recent replacement/rehabilitation projects,
Coded mains as either cement lined or unlined,
Incorporated institutional knowledge relating to water main breakages and problem areas.
Created a Town-wide water system network and Master Geodatabase for use on the project
Upon completion of the above Geodatabase information, system connectivity issues were identified
and resolved prior to creation of the hydraulic model. These issues included the following:
Hydrants that did not have an accompanying hydrant lateral or hydrant gate valve were
provided a hydrant lateral and where appropriate a gate valve. While the hydrant laterals are
not necessary for water modeling purposes, it is helpful to display them as a background layer
to indicate which water main a specific hydrant is connected to. Also, hydrants located at
corners of intersections and on roads with multiple water mains can contribute to inaccuracies
within the model.
Hydrant valves that were shown in back of the hydrants or on the opposite side of the water
main were reinserted in the correct location.
Water main pipe segments were broken at junctions with other pipes and not at gate valves.
Breaking the water main pipe segments at gate valves will increase the accuracy and usability
of the water model. This will also increase the number of nodes/locations to check pressures
METER #27
METER #55
METER #107
Chickatawbut Reservoir #1
Great Blue Hill Reservoir
Chickatawbut Reservoir #2
¯
Canton
Quincy
Boston
Randolph
LegendLow Pressure Zone
High Pressure Zone
") Emergency Connection
KJ MWRA Meter
UT Water Tank
Water Pipe4 - inch diameter or less
6 - inch diameter
8 - inch diameter
10 - inch diameter
12 - inch diameter
16 - inch diameter
20 - inch diameter
Town of MiltonMassachusetts
Figure 1.1Existing Water Distribution System
1-2
and fire flows as well as be beneficial for flushing and leak detection programs in determining
the effects on the water system of closing certain gate valves. BETA used an automated
process within the WaterGems software to break and snap water pipe segments to the
appropriate gate valve.
Missing fittings or pipe junctions were created as part of the network development process.
Hydraulic modeling requires a point to exist at the end of each pipe segment. These points
were created, reviewed and then were incorporated back into the existing Water System
Geodatabase.
Pipe segments that were not snapped correctly (i.e. some pipes were not broken at junctions,
pipe segments were disconnected where they should be snapped together, etc.), were snapped
or broken properly to improve the accuracy of the hydraulic modeling output.
Data compiled using the Town’s updated Geodatabase system, as shown in Table 1.1, indicates that
Milton’s water distribution system consists of approximately 737,562 feet or 140 miles of 2-inch
through 20-inch water main. Of the 140 miles of water main, approximately 188,606 feet (35.7miles)
or about 26 percent of the total length of water main in the distribution system is unlined.
The number of hydrants, main gate valves, MWRA Meters, Water Storage Tanks and Emergency
connections within the system are shown in Table 1.2.
TABLE 1.2 - APPURTENANCES
Appurtenance Quantity
Hydrants 1,191
Main Gate Valves 2,316
MWRA Meters 3
Water Storage Tanks 3
Emergency Connections 9
TABLE 1.1 - SUMMARY OF EXISTING WATER SYSTEM
Main Size
(inch)
Unlined Main Cement Lined Main
(feet) (%) (feet) (%)
≤ 4 1,410 0.2 5,744 0.8
6 131,023 17.8 97,003 13.1
8 30,118 4.1 252,812 34.3
10 9,346 1.3 23,401 3.2
12 16,709 2.2 159,277 21.6
16 0 0.0 10,716 1.4
20 0 0.0 3 0.0
Totals 188,606 25.6 548,956 74.4
1-3
The Town’s water distribution system has been installed since the turn of the century as shown in
Table 1.3.
Table 1.3 - WATER MAIN INSTALLED BY DECADE
Decade Length (feet) % of System
1880’s Total 73 0.01
1910’s Total 130,574 17.70
1920’s Total 81,228 11.01
1930’s Total 130,568 17.70
1940’s Total 44,556 6.04
1950’s Total 69,797 9.46
1960’s Total 50,632 6.87
1970’s Total 40,393 5.48
1980’s Total 49,449 6.71
1990’s Total 35,814 4.86
2000’s Total 72,955 9.89
2010’s Total 31,523 4.27
Total: 737,562
The above table shows that approximately 46.4% of the Town’s water mains were installed prior to
1940.
1.3. Regulatory Requirements
A water distribution system has two primary functions. The first function is to provide adequate
water supply for domestic purposes and the second is to provide adequate pressures and flows for fire
protection. Required fire flow in any area depends on several factors. According to the American
Water Works Association (AWWA) Manual M-31 and the Insurance Services Offices (ISO, factors
include the type of building structure, distance between buildings and the building’s footprint. The
largest fire flow demands generally occur in business and industrial areas and can exceed 3,500 gpm.
Fire flows in excess of 3,500 gpm become the responsibility of the building owner. Table 1.4 shows
the residential standards used to determine adequate fire flows for one and two family buildings.
Table 1.4 – RECOMMENDED FIRE FLOW FOR ONE AND TWO
FAMILY DWELLINGS
Distance Between Buildings Needed Fire Flow
More than 100’ 500 gpm
31’ – 100’ 750 gpm
11’ – 31’ 1,000 gpm
Less than 11’ 1,500 gpm
Recommended fire flows are defined as the minimum fire flow rate recommended while maintaining
a minimum water pressure of 20 pounds per square inch (psi) under all design conditions per MGL
310CMR 22.
1-4
In addition to the fire flow requirements, the ISO has established recommended time duration
requirements during which the fire flow should be maintained. The ISO Standards for time duration
for recommended fire flows are shown in Table 1.5.
Table 1.5 – ISO FIRE FLOW RECOMMENDATIONS
Recommended Fire Flow
(gpm)
Recommended
Duration (hours)
2,500 and less 2
3,000 3
3,500 3
4,000 and greater 4
1.4. Hydrant Flow and C-Value Testing
Field testing is an important part of a water distribution system analysis. A water distribution system
must provide adequate service and meet average day and maximum day demands in accordance with
AWWA, DEP and ISO standards. A minimum of 20 pounds per square inch (psi) must be maintained
under all design conditions per MGL 310 CMR 22 and DEP regulations. Hydrant flow and C-Value
testing assisted in assessment of the distribution system’s ability to meet these requirements. Results
from the field tests are also compared to results obtained from the model. The model is then
calibrated to reflect actual field conditions.
1.4.1 Hydrant Flow Testing A hydrant flow test is conducted to determine the volume of available water from a hydrant at a
pressure of 20 psi. BETA employees assisted the Town during the 12 hydrant flow tests conducted in
2014. In addition, BETA reviewed a total of 60 previous hydrant flow test results completed by Town
personnel; 40 tests were completed in 2012 and 20 tests completed in 2013 as shown in Table 1.6.
The results from the hydrant flow tests program were used to assist in the calibration of the hydraulic
model to actual field conditions. The 6 retested hydrant flow tests conducted in 2014 were all located
within the high pressure zone and were conducted to verify information (tests results) retrieved in
either 2012 or 2013. The retests were conducted where there was significant inconsistency between
the initial field test result and the simulated model run concerning the volume of availability water
from a hydrant. Location of the 72 hydrant fire flow tests are shown on Fig 1.2 and tabulations of the
field test results are provided in Appendix A of this report.
Table No. 1.6 - HYDRANT FLOW TESTS
# of Tests in # of Tests in
Test Year Low Pressure Zone High Pressure Zone Total # of tests
2012 28 12 40
2013 8 12 20
2014 0 6 6
2014 (Retest) 0 6 6
Total # of Tests 36 36 72
Fifteen out of the seventy-two sites tested, did not meet the minimum ISO requirement of 500 gallons
per minute (gpm) at 20 psi. The fifteen sites were typically in areas with old, unlined, 6-inch diameter
43
1
9
65
7
2
77
42
54
65
66
47
48
68
50
34
55
10
56
53
5238
35
11
36
59
2217
58
23
162526
39
57
3332
1413
37
7561
51
63
72
2930
40
6471
45
62
70
28 44
6076
41
24B
24A
43, 67
46, 69
19, 20
49, 74
31, 73
METER #27
METER #55
METER #107
Chickatawbut Reservoir #1Great Blue Hill Reservoir
Chickatawbut Reservoir #2
¯
Canton
Quincy
Boston
Randolph
Town of MiltonMassachusetts
Figure 1.2Fire Flow Test Locations
Legend
Fire Flow Test Location
Low Pressure Zone
High Pressure Zone
") Emergency Connection
KJ MWRA Meter
UT Water Tank
4 - inch diameter or less
6 - inch diameter
8 - inch diameter
10 - inch diameter
12 - inch diameter
16 - inch diameter
20 - inch diameter
þ
Water Pipe
1-5
water main within the low pressure system. Chapter 9 of the DEP Guidelines states that water mains
designed to provide fire flow shall not be smaller than 8-inches in diameter. Low volume of available
water typically indicates that there could be a closed or partially closed gated valve in the area, that
the pipe has excessive tuberculation or that the water main is undersized. In addition, there are
concerns in the Brush Hill Road, Harland Street, Randolph and Canton Avenue areas due to
discrepancies in hydrant flow tests conducted in close proximity to one another. Town personnel
confirmed the areas of concern. Typically, these results indicate that there may be gates in the closed
or partially closed position. BETA and town personnel believe that that is likely the case in the above
named areas.
1.4.2. C-Value Testing
A pipe condition test (C-Value Testing) is conducted to estimate the hydraulic capacity of the pipe
and provides means to estimate the roughness coefficient (Hazen Williams C-Value) which is used
by water model to calculate the head loss due to internal friction on the water, by the pipe wall. The
coefficient C is a function of the roughness of the internal surface of the pipe and is directly
proportional to the carrying capacity of the water pipe. According to AWWA M-32, a typical C-
Value for a newly scraped 12-inch cast iron water main is approximately 120. Therefore, a C-Value
of 60 indicates that the carrying capacity of the pipe has been reduced to half the original capacity at
the same head loss. It is generally accepted in the industry that when a pipe’s capacity deteriorates to
50 percent of its original capacity it should be replaced or rehabilitated.
Town field personnel with the assistance of BETA personnel performed a total of eight “C-Value”
flow (CVF) tests on water mains throughout the Town. Five CVF tests were conducted within the
high pressure zone and three tests were conducted within the low pressure zone, as shown in Table
1.7. A location map of the 8 “C-Value” flow tests is provided as Fig 1.3 and tabulations of the test
results are presented in Appendix B of this report.
Table No. 1.7 – “C VALUE” FLOW TESTS
Street Name Pressure
Zone
Pipe Diameter
(in)
Pipe Material C-Value Actual Q
(gpm)
Hillside Street High 8 CICL 94 1071
Blue Hill Avenue High 6 CI 39 417
Brush Hill Road High 8 CICL 37 791
Canton Avenue High 8 CI 149 1699
Whittier Road High 8 CICL 129 1526
Wendell Park Low 6 CICL 91 769
Brandon Road Low 6 CI 109 264
Antwerp Street Low 6 CI/CICL 20 186
CI – Cast Iron
CICL – Cast Iron Cement Lined
Results indicate that three out of the eight sites tested had a C-Value of 60 or less which is considered
a low CVF test result. A low CVF test result typically indicates that the water main has excessive
tuberculation and should be either replaced or rehabilitated. The above CVF results indicate that Blue
1
87
6
3
2
5
4
METER #27
METER #55
Chickatawbut Reservoir #1Great Blue Hill Reservoir
Chickatawbut Reservoir #2
METER #107
¯
Canton
Quincy
Boston
Randolph
Town of MiltonMassachusetts
Figure 1.3C-Value Test Locations
Legend
C-Value Test Location
Low Pressure Zone
High Pressure Zone
") Emergency Connection
KJ MWRA Meter
UT Water Tank
4 - inch diameter or less
6 - inch diameter
8 - inch diameter
10 - inch diameter
12 - inch diameter
16 - inch diameter
20 - inch diameter
þ
Water Pipe
1-6
Hill Avenue, Brush Hill Road and Antwerp Street warrant some form of replacement/rehabilitation
work.
1.5. Hydraulic Model Creation and Calibration
The hydraulic model was created by importing the water network and attribute data from the Master
Geodatabase into Bentley WaterGEMS V8i® software. All data points such as junctions, valves and
end caps were imported as nodes and water mains were imported as lines. The water demand
information was added to the nodes within the model.
When creating a water distribution system demand database, the average day demand (ADD) and
maximum day demand (MDD) for the distribution system are required. Annual water demand
includes residential, commercial, industrial and unaccounted water usage. AWWA Manual M-32
defines ADD as the annual water demand divided by 365 days which represents the average water
demand that a given water distribution system experiences over a one day period. MDD is defined as
the volume of water used on the highest consumption day in a year. The ADD was determined to be
2.46 mgd using 2011-2013 MWRA water meter flow records as shown in Table 1.8. The low
pressure zone observed a MDD of 5.76 mgd on September 15, 2011 and the high pressure zone
observed a MDD of 2.01 mgd on June 6, 2011. The model transferred the water demands to the water
network nodes by using Geodatabase parcel information, which has the demand data for that location.