USA > Massachusetts > Middlesex County > Somerville > Report of the city of Somerville 1889 > Part 18
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Elevations of door sills in both of these districts were obtained from actual surveys and recorded for reference ; and the static pres- sure due to the head of water estimated from high water mark in the resevoir, was computed.
From information thus obtained the exact condition of the water supply of every house visited can be definitely stated. A table has also been prepared showing the number of houses in the high service. territory having a pressure less than 10-20-30-40-50 pounds, etc., which will be found on page 318.
To determine the theoretical area of the high service territory to be supplied, it was necessary to fix on a minimum static pressure in pounds, which will be the limit between high and low service.
A pressure of 37 pounds was adopted as this limit. This pressure is equal to a head of about 87 feet, or an elevation of 70 feet above mean low water ; and would be defined by a contour or level line run around the hills at an elevation 70 feet above mean low water,. and the area enclosed by this contour or level line would be the high ser- vice territory or area.
The area included in these high service districts is as follows :-
Winter Hill,
136 acres.
Spring, Central and Prospect Hills 242 acres.
Total 378 acres.
305
APPENDICES TO CITY ENGINEER'S REPORT.
These areas are the theoretical areas which are in need of a high service pressure. They are subject to considerable increase by means of local conditions independent of the pressure required to furnish a domestic supply.
1st. The contour line of 70 feet above mean low water intersects street lines in such a manner that, were the theoretical line followed it would be necessary to gate off one-half of the mains in many of the streets, and thereby produce a large number of dead ends. That the water might not become turbid, it would be necessary ' that blow-offs be placed at these dead ends, and the pipes emptied at regular intervals, to keep the water pure. This work in itself would not be very difficult, but it would be a constant burden to the Super- intendent, and a source of trouble to the consumer. The effect would be to prevent circulation in the connecting pipes, and lessen the discharge; if the pipes were connected they would feed from both directions.
2d. The condition of the cement-lined pipes is such that the increased pressure from the high service will cause many breaks ; and if these pipes must be relaid it will add but very little to the cost to avoid these dead ends when these mains are relaid.
3d. The present mains in Somerville avenue are entirely too small to provide for an efficient fire protection, and must be relaid with larger pipes.
It is highly probable that land adjoining the Fitchburg railroad will be used for manufacturing purposes entirely, in the near future ; and should this be the case a larger amount of water, and conse- quently mains of very much larger diameter, will be required for fire protection. If the high service system is properly designed, the present low service mains can be used for domestic purposes entirely, and the high service mains used for fire purposes. For these reasons I have avoided dead ends by enlarging the high service districts, and have increased the areas as follows :-
Winter Hill
162 acres.
Spring, Central and Prospect Hills 355 acres.
(See page 304.) Total 517 acres.
Insufficient supply to the high lands is due to two causes. 1st. The elevation of Spring and Winter Hills is so nearly the same as the elevation of high water at the Mystic reservoir that there
306
ANNUAL REPORTS.
is not sufficient head or pressure to carry the water from the reser- voir to these elevations.
The following table shows the elevation of the reservoir, Spring and Winter Hills, the static pressure due to the elevation and the recorded pressure at the house :
Location.
Elevation of Door Sill Above Mean Low Water.
Elevation of Guage at House.
Recorded
Static Pressure. Pressure.
Lbs.
Lbs.
Loss of Head. Lbs.
Mystic Reservoir
157
Spring Hill
145.6
141.6
2
5
Winter Hill .
141.7
145.3
2
5
3
The elevation and pressure given on Winter Hill is not that of the highest door sill, as there was no means of observing the pressure at the highest point. The elevation of the highest door sill on Winter Hill is 148.2.
The loss of head is due to the large consumption in the lower parts of the city.
2nd. The limited capacity of the distribution system. On the Winter Hill system the loss is not so apparent. For although there is but one 8-inch pipe in the district, that on Broadway, the 24 and 30-inch mains are so situated that the pressure is maintained. The average loss of head is two pounds.
The same is true on the Spring Hill district ; except that the whole district is supplied from the 12-inch main on Central street.
The average Joss of head on Spring, Central and Prospect Hills is about five pounds.
No experiments have been made to determine the efficiency of the present distribution system in the high service district ; although a strict interpretation of the order might include such an investigation.
It would be necessary to make a large number of experiments with hose streams at the hydrants, before a satisfactory report could be made, and for this reason this part of the work has not been car- ried out.
In preparing a plan and estimate for a high service supply, the first question to be decided is the quantity of water which may be required.
307
APPENDICES TO CITY ENGINEER'S REPORT.
Water will be required for two purposes.
1st. Domestic consumption.
2nd. Fire protection.
From measurements made in Boston on the quantity of water used in private houses it was estimated that the average daily consumption was about 25 gallons per inhabitant per day. From records of quantity of water used in other cities it has been estimated that the maximum daily consumption is nearly 100 per cent. larger than the average daily consumption.
From these records I have estimated that the average daily con- sumption will be 30 gallons and the maximum daily average 60 gal- lons per inhabitant.
The following table shows the average daily consumption of 13 cities and towns having about 30 gallons daily average consumption :
TABLE SHOWING THE DAILY AVERAGE CONSUMPTION PER IN- HABITANT OF THIRTEEN CITIES OR TOWNS.
CITY OR Town.
Population in 1885.
Daily Average Consump. tion in gallons.
Arlington
1,785
31
Brookline
9,196
71
Cambridge
59,658
58
Chelsea. .
25,709
69
Framingham.
8,275
42
Lowell.
64,107
59
Lynn
45,867
50
Marblehead
7,517
29
Milford.
9,343
32
Natick
8,460
33
Newton
19,759
36
Springfield
33,340
96
Waltham.
14,609
39
In order to compute the estimated growth in population of the high service districts, a table has been prepared showing the rate of increase in population of various cities and towns ; a copy of this table is given below.
308
ANNUAL REPORTS.
TABLE SHOWING THE PERCENTAGE OF INCREASE IN POPULA- TION IN PERIODS OF FIVE YEARS IN SEVERAL CITIES AND SUBURBAN TOWNS.
TABLE 1.
CITIES.
Popula- tion in 1885.
PERCENTAGE OF INCREASE-FIVE YEARLY PERIODS.
1850-55.
1855-60.
1860-65.
1865-70. 1870-75. 1875-80.
1880-85.
Av'ge.
Lynn . .
45,867
10
21
9
36
15
17
20
18
Springfield .
37,575
17
10
45
21
17
13
19
Chelsea.
25,709
50
32
8
29
11
1-10
18
20
Somerville ·
29,971
70
39
16
57
49
14
20
38
Fall River. .
56,870
10
11
24
53
69
8
16
27
New Bedford
33,393
24
9
. .
2
21
3
24
12
Charlestown.
37,673
26
19
5
7
11
1
13
12
Holyoke .. ...
27,859
43
8
13
90
51
35
32
39
Average increase for eight cities, 23.
SUBURBAN TOWNS AND CITIES.
TABLE 2.
TOWNS.
Popula- tion in 1885.
FIVE YEARLY PERIODS.
1850-55. 1855-60. 1860-65. 1865-70. 1870-75. 1875-80. 1880-85.
Av'ge.
Cambridge.
59,658
35
27
12
36
27
10
12
23
Melrose .
6,101
57
28
13
19
17
14
34
26
Newton .
19,759
30
24
7
43
25
5
18
22
Watertown
6,238
26
15
14
18
7
15
16
Brookline.
9,196
48
40
1
26
21
14
21
Quincy
12,145
18
14
11
23
15
15
16
Malden
16,407
30
27
17
8
47
11
37
25
Waltham
. . ..
14,609
35
6
8
32
10
17
25
19
Brighton
. .
8,516
23
18
14
28
25
8
27
21
W. Roxbury. .
17,425
. .
. .
. .
. .
. .
24
. .
Average increase, 21.
From the above tables it will be evident that an average increase of 25 per cent. in five years would be a fair estimate of a probable increase in population for the next twenty-five years at least.
As a further basis on which to estimate the further growth of the city, a table was prepared showing the population from actual count made in the high service districts, in the winter of 1888-89, and from
309
APPENDICES TO CITY ENGINEER'S REPORT.
this the estimated growth of the city, by a 25 per cent. five yearly increase, to the year 1925.
A copy of this table is given below :
TABLE SHOWING THE POPULATION OF THE HIGH SERVICE DISTRICT FROM ACTUAL COUNT IN 1888, AND A FIVE YEARLY INCREASE OF 25 PER CENT. TO 1925.
TABLE 3.
YEAR
Winter Hill, Southweet of Central Street.
Winter Hill, Northeast of Central Street.
Spring Hill, Southwest of Central Street.
Central and Pros- pect Hill, South- east of Central St.
1888
1,189
1,408
1,589
3,116
1890
1,307
1,548
1,747
3,427
1895
1,634
1,910
2,184
4,284
1900
2,042
2,388
2,730
5,355
1905
2,552
2,985
3,412
6,694
1910
3,190
3,731
4,265
8,367
1915
3,987
4,664
5,331
10,459
1920
4,984
5,710
6,664
13,074
1925
6,230
7,137
8,330
16,342
A third table has been prepared showing the estimated population in the high service districts, on the basis of 56.5 population to the acre, estimated from the report of the Somerville Board of Health. (See City Reports for 1887, page 211, Health District No. 2.)
A copy of this table is given below :
POPULATION ESTIMATED ON A BASIS OF 56.5 TO THE ACRE.
TABLE 4.
Winter Hill, North- west of Central Street.
Winter Hill, North- east of Central Street.
Spring Hill, South- west of Central Street.
Spring Hill, South - east of Central Street.
4,407
4,746
10,622
9,435
By a comparison of tables 3 and 4 it will be seen that in table 3 the population computed for the year 1915 does not materially differ from that given in table 4, except that the figures given in the third column of table 3 are considerably less than in table 4. This differ- ence is accounted for by the fact that a large part of this district is unoccupied.
.
310
ANNUAL REPORTS.
The figures referred to in tables 3 and 4 are so nearly alike that I have accepted those in table 4 as correct, for purposes of an esti- mate, and have prepared a table showing the estimated growth for five yearly periods, assuming that the population in 1915 will be equal to a population of 56.5 per acre.
TABLE SHOWING THE POPULATION TO 1915, FOR PERIODS OF FIVE YEARS. TABLE 5.
Year.
Winter Hill, Northwest of Central Street.
Winter Hill, Northeast of Central Street.
Spring Hill, Southwest of Central Street.
Central & Pros- pect Hills, Southeast of Central Street.
Total.
1890
1,445
1,555
3,480
3,091
9,571
1895
1,806
1,944
4,350
3,864
11,964
1900
2,257
2,430
5,438
4,830
14,369
1905
2,821
3,038
6,798
6,038
19,695
1910
3,526
3,797
8,498
7,548
23,369
1915
4,407
4,746
10,622
9,435
29,210
Upon this basis I. have computed the average daily consumption, allowing 30 gallons per inhabitant per day.
TABLE SHOWING THE AVERAGE DAILY CONSUMPTION, ALLOW- ING THIRTY GALLONS PER INHABITANT PER DAY.
TABLE 6.
YEAR.
Winter Hill, Northwest of Central Street.
Winter Hill, Southeast of Central Street.
Spring Hill, Southwest of Central Street.
Central & Pros- pect Hills, Southeast of Central Street.
Total gals. per minute.
1890
43,350
46,650
104,400
92,730
200
1895
54,180
58,320
130,500
115,920
250
1900
67,710
72,900
163,140
144,900
310
1905
84,630
96,140
203,940
181,140
390
1910
105,780
113,960
254,940
226,440
485
1915
132,210
142,380
318,660
283,050
608
These tables have been prepared, studied, and compared with con- siderable care, and in my opinion give a fair basis for fixing the sizes of the mains and distribution system and for estimating the cost of the proposed scheme for a high service supply.
In designing this system of works it is necessary to pay particular attention to the second demand for an increased supply.
311
APPENDICES TO CITY ENGINEER'S REPORT.
FIRE PROTECTION.
This division of the subject has required considerable study to determine just what quantity of water should be furnished for fire service. A maximum quantity of 1400 gallons per minute has been provided for in the distribution for Spring, Central and Prospect Hills, and 600 gallons per minute for Winter Hill. These quantities are equivalent to seven hydrant streams and three hydrant streams respectively.
From these figures and from figures given in table 6, the quantity of water to be provided for in 1915 would be as follows :
Gallons Per Minute.
For daily average consumption
608
For fire service
2,000
2,608
For maximum daily consumption
1,217
For fire service
2,000
Total .
3,217
As regards the quantity of water used for fire service, it is re- ported that at the recent fire at Marblehead the estimated quantity of water used was about 50,000 gallons per hour, or 833 gallons per minute ; even this quantity was not sufficient for the demand, as it was reported that at some of the hydrants no water could be ob- tained during the fire. If more water had been delivered more would have been used.
Several plans for a high service supply have been studied and estimated, all essentially the same in the mains and distribution system, but providing for different locations of the pumping stations.
The plan which was found to be most economical and practical is as follows :
A pumping station at the junction of Central and Medford Streets ; an iron tank on Spring Hill, 30 feet in diameter and 70 feet high ; a 14-inch force main to Spring Hill through Central Street, Highland Avenue and Belmont Street ; a 12-inch force main to Winter Hill through Central Street.
The 14-inch force main to Spring Hill is not large enough to sup- ply the quantity of water which the distribution system will deliver ;
312
ANNUAL REPORTS.
but it is large enough for the maximum consumption for fifteen years.
When the increased cost of pumping, which would be occasioned by pumping through a small force main, is more than the interest of the cost of laying a 12-inch main parallel with the 14-inch main to the junction of Highland avenue and Central Street, a second force main should be laid.
The proposed buildings at the pumping station will consist of an engine and boiler house, engineer's tenement, coal shed and chimney.
The plan recommended provides for an engine of a capacity of 2,000,000 gallons in 24 hours.
A 2,000,000 engine will furnish the daily average consumption until 1910 ; at that time it will not be necessary to run the engine more than eight hours a day, and if occasion require it would furnish 1900 gallons a minute for the fire service.
This amount would include the daily average consumption, and if it were necessary to run the engine at its full capacity for fire service it would be done by drawing upon the quantity pumped for domes- tic use.
In considering the capacity of an engine required for the proposed high service, aud especially in comparing our needs with those of other cities where a pumping engine is used in connection with a distributing reservoir (as is the plan adopted for the Chelsea high service supply), it should be remembered that the plans are not at all similar and cannot be compared. In the Chelsea plan the reservoir is probably large enough to hold three days' supply ; and if the water in the reservoir is kept approximately near the high water mark, the reservoir would hold a quantity more than sufficient for fire service, and the pumping engine would not be called upon to perform any additional duty in time of fire.
If we could build a reservoir holding 1,000,000 gallons, a smaller engine could be used ; for in that case the reservoir could be relied upon in case of fire without relying directly on the pumping engine to maintain the pressure and the supply for fire purposes, and the capacity of the pumping engine would be simply that required to furnish the daily average consumption.
As there is no location on which a reservoir can be built which would furnish the required head a tank must be substituted for the reservoir and the pumping engine must be provided to furnish the maximum quantity required for fire service.
313
APPENDICES TO CITY ENGINEER'S REPORT.
The capacity required depends not on the daily average consump- tion for a certain period, or even on the maximum consumption, but on the quantity required for the largest number of fire streams that may be needed.
In direct pumping, with an iron tank, the pumping engine is the only source of supply ; and if the capacity of the pumps is less than the quantity which may ever be required for fire purposes. the effi- ciency of the fire department will be limited by just that quantity which the pumps fail to deliver to the fire engines ; and in case of a large fire the actual loss from a deficiency in the supply of water would be far in excess of the amount saved by reducing the capacity of the pumps to bring the cost of the pumping plant to the lowest limit.
The tank should be of such dimension as will hold a quantity of water equal to the daily average consumption in 1905. The tank will be 30 feet in diameter and 70 feet high, and will hold about 371,000 gallons.
In fixing the height of the tank it must be remembered that all the water used for domestic consumption must be raised to the eleva- tion of the tanks in the houses on the summits of the hills before it will be available for domestic use. The elevation to which the water must be raised has been assumed at 20 feet above the tops of the hills, equal to an elevation above mean low water of 176.
In addition to this height a quantity for storage must be provided equal to one-half of the daily average consumption in 1905. A tank of 30 feet in diameter must be at least 50 feet high to provide the required storage. The total height of the tank should be 70 feet, and the top should be placed at an elevation of 216 feet above mean low water. This elevation is equivalent to a head of 70 feet on the top of Spring Hill, or a pressure of about 30 pounds. If a tank of a smaller diameter and height were designed, it would be necessary in the near future to run the pumping engine for a longer period than would be considered a day's work for an engineer, and two men would be required at the pumping station instead of one, necessitat- ing an increase of about $900 a year, equal to the interest on $22,500 at 4 per cent.
From these figures it is evident that a considerable sum might be expended for a larger tank rather than to increase the cost of the running expenses at the pumping station.
314
ANNUAL REPORTS.
ESTIMATE OF COST OF PROPOSED HIGH SERVICE.
Buildings, including engineer's tenement, engine and
boiler house, chimmey and coal shed. . $11,500 00
Pumping engine and boilers in place with connections, engine capacity 2,000,000 gallons in 24 hours 8,500 00
Land
Tank, 30 feet in diameter and 70 feet high .
10,500 00
Land for tank
4,000 00
Fourteen-inch force main to Spring Hill 9,375 00
Twelve-inch force main to Winter Hill 2,300 00
Distribution system
66,600 00
Relaying 100 feet 30-inch cement pipe with iron, con- nections with sewer, re-arranging present pipes at Central and Medford streets, check valves
900 00
Fifty feet 18-inch suction . 200 00
$117,375 00
Add 10 per cent. for contingencies 11,737 50
Total . $129,112 50
This estimate provides for relaying the large part of the present distribution in the high service districts. But it is not necessary that these changes be made immediately. A certain amount could be done from year to year until the whole scheme is carried out. The essential parts of the works which should be built immediately are the pumping station and pumping plant, tank and force mains. When these essential features are built the present distribution system can be temporarily used by placing a few gates on the street mains to separate the high and low service districts.
For this work an immediate expenditure would be required as follows :
Buildings, engines, etc. $20,000 00
Land for pumping station and tank
7,500 00
Tank .
. 10,500 00
Force mains to Spring and Winter Hills
· 11,675 00
Connections
1,100 00
50,775 00
Add 10 per cent. for contingencies
5,077 50
·
.
$55,852 50
-
3,500 00
315
APPENDICES TO CITY ENGINEER'S REPORT.
Objections to this scheme may arise from fear that the cost may exceed the estimate ; that such a large expenditure would be ex- travagant ; that such a large outlay will increase the funded debt and the tax rate. It may be said that we ought to be contented with our present supply and that an increased fire service is not needed from the fact that we have never had large fires ; but does this prove that we may not in the future have a large fire? It may be stated that most of the trouble caused by a lack of pressure is over a small area. But that is not true. An area equal to at least one-sixth of the area of the city is as much entitled to an efficient water service as the other five-sixths.
Our city has not yet been visited by an extensive conflagration ; but, should a large fire occur the value of property which might be destroyed would be far in excess of the interest on the cost of the proposed work, and possibly the loss sustained might be in excess of the total cost of the works.
In considering the cost of the proposed works it may be well to consider what may be saved in the cost of maintaining steamers to properly protect these high portions of the city, should the City Council fail to carry out the proposed high service supply on a broad and comprehensive plan.
To afford sufficient protection to Spring and Winter Hills when the districts are compactly built two steamers will be required.
The annual cost of maintainance for two steamers, not including repairs, but simply for salaries and keeping and shoeing horses, is estimated to be $6200. This amount would capitalize $155,000 at 4 per cent. ; a sum far in excess of the estimate of the cost of the whole improvement.
From the description of the mains and distribution system given on pages 302 and 303 it is evident that the district southwest of the Boston and Lowell Railroad is practically supplied from the 12-inch main in Central street and the 8-inch from Washington Street.
The quantity of water which a 12 and 8-inch pipe can be depended on to deliver at the greatest allowable velocity is about 1400 gallons per minute, without a serious loss of head. The smallest quantity of water which will be required for domestic consumption in this district is about 1000 gallons per minute.
From these figures it is evident that but 400 gallons per minute can be relied upon for fire protection without drawing upon the quantity required for domestic consumption.
316
ANNUAL REPORTS.
This quantity would be sufficient for two hydrant streams or one steam fire engine.
In making the figures I have not estimated on the quantity of water which would be taken from the 8-inch pipe through Washing- ton street by the local demands east of Union square.
The quantity of water above mentioned which a 12 and 8-inch pipe would deliver can be increased somewhat ; but it can only be done by a still greater increase in the loss of head, which would be of vital importance in case of fire, as the increased delivery would be more than offset by the loss of head.
An analysis of the distribution might be still further extended and would show that the sizes of pipe over the entire city are all very much smaller than they should be to give an efficient fire protection and provide for the average daily consumption for domestic purposes.
The statements referring to the sizes of present distribution are not strictly called for by the order of the City Council, but are given for information, that the committee and the public may be made aware of the actual condition of the distribution system and of the danger of serious loss to property in case of fire from a deficient water supply.
For the same reason I have not investigated the question of in- creasing the present distribution, and shall submit no plan. Such an investigation would be of little value without extended experiments on the present distribution, to ascertain the capacity of the present system.
There are large areas north of Central Street and west of Highland Avenue which are not yet occupied for building purposes, for which it does not appear that any provision has been made for water distri- bution according to any system. There should be a comprehensive plan prepared, showing a system of distribution large enough for all the future demands, and extension could then be made in a systematic manner. Hydrants should also be located systematically to produce the best results, and with a view to the future use when our territory will be more thickly settled.
I would respectfully recommend that these subjects be brought to the attention of the City Council for its consideration. The present distribution was planned for a small town with a scattered popula- tion, and was probably large enough for the town at the time the water was introduced. At that time the population was about 15,000.
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