USA > Massachusetts > Norfolk County > Norwood > Norwood annual report 1908-1911 > Part 28
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Norwood is situated upon the Neponset river, which is a comparatively small stream running through a populous district and wholly inadequate for the proper dilution and dissipation of the crude sewage from the cities and towns through which it flows. An effort has been made in recent years to secure the purification of the sewage and mill wastes already finding its way into the Neponset river and it was obviously undesirable for Norwood to make any effort to discharge its sewage untreated into the river; consequently, from the beginning, the intention was to build a sewage disposal plant.
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Approximately 6 1 -2 acres of sand filter beds have been pro- vided which, upon conservative estimate, should be sufficient to care for the sewage of from 4000 to 7000 people. In fact, a number of filtration areas in this State are purifying sewage from considerably larger populations. The character of the sand of which the filters are built is excellent for the purposes of purification. It is rather coarser than the average for disposal plants in this vicinity, and when first put into use may not pro- duce an effluent quite as pure as would be produced by a finer material. However, as the organic matter from the sewage accumulates in the upper stratum of sand, the effective size of the material will be reduced and a very satisfactory effluent should be produced.
Every effort has been made to so design and construct the disposal plant as to make it very efficient. A settling basin has been provided through which the sewage will pass at a rate suf- ficiently low to permit of the precipitation of the matters carried in suspension. The settled sewage will flow from the sludge tank into a dosing tank, in which it will be allowed to accumu- late to a volume of about 110,000 gallons. When the tank con- tains this quantity of sewage, a siphon will automatically dis- charge the contents into a line of pipe, through which it will pass onto one of the filters. Two siphons have been provided and are so constructed as to automatically and alternately dis- charge the contents of the tank. It will thus be possible for the attendant to leave the plant for a considerable length of time, during which the tank may twice become full and will be dis- charged onto two different filters. The dosing tank will be thus emptied by means of the siphon in approximately thirty minutes, the sewage will be applied to the filter in a very short length of time. There are several advantages of this method of procedure. During the winter when the surface of the filters may be frozen or covered with snow and perhaps also with ice, the sewage will be discharged in sufficient quantity and so rapidly that its warmth will be largely available for thawing any frost, snow or ice with
29
which it may come in contact. If, on the other hand, no dos- ing tank had been provided, the sewage would run onto the beds for hours in a comparatively small stream, and in this way would become chilled, so that its efficiency for thawing the sur- face of the bed would be comparatively slight. The provision of a covered dosing tank also reduces to a minimum the loss of the warmth of the sewage while it is accumulating preparatory to being discharged upon the filters. In summer, although there is no ice to be thawed, the application of the sewage in one comparatively large dose, is of value in securing a more uni- form distribution of the water over the surface of the filter, thus providing a nearly uniform amount of work for all parts of the bed.
The benefits derived from the application of sewage in doses, rather than continuously, are still further increased by means of the surface distributors which have been provided for all of the beds. These distributors are not new or novel, having been used for many years at Brockton, Worcester and other places. They consist of shallow boxes with concrete bottoms. and wooden sides. The sides are provided with several openings controlled by gates, so that the sewage which is discharged by the main distributor pipes into the surface distributors, can be applied to the filters at a number of different points, thus aiding in its uniform distribution.
The removal of the suspended matter carried by the sewage before it is applied to the filters will reduce the amount of clean- ing required by the filter beds, and will probably also render them capable of providing for a somewhat greater quantity of sewage. The suspended matters removed from the sewage will accumulate in the sedimentation basin and must, from time to- time, be removed from it. The length of time during which it will be advisable to allow these solid matters to accumulate must be determined by experience. The tank should be inspected frequently and the degree of activity of decomposition should be noted. It will be found that when the sewage has been in the
30
tank but a day or two, there will be comparatively little decom- position, as evidenced by the liberation of gas. After the tank has been in use for a period of three to six weeks, the activity of decomposition will be very greatly increased. When there is evidence of active fermentation, the tank should be cleaned out, the accumulated sludge being discharged onto the sludge bed provided for that purpose.
There is more or less conflicting evidence of the benefits and detriments, of the application to sand filters of stale or put- rid sewage. The sewage received at the disposal plant will of necessity have undergone considerable decomposition due to the long time it will have remained in the inverted siphon. The de- composition of sewage in the settling basin will add to the gases and other products of decomposition contained in the sewage, so that until the quantity of sewage is sufficiently great to reduce materially the length of time occupied in passing through the siphon, it will be very desirable to clean the sludge basin at com- paratively frequent intervals if a reasonably fresh sewage is to be discharged onto the filter bed. Experience seems to indicate that better results are obtained by the filtration of a fresh sewage than one which has undergone considerable putrefaction, and for this reason it would appear to be desirable to use every ef- fort to apply the sewage to the filters in as fresh a state as pos- sible.
It was impracticable to construct the filters at an elevation as high above the water in the Neponset river as would be de- sirable. On this account particular attention has been given to providing a very generous system of under-drainage. Each bed is supplied with five underdrains, reducing the lateral dis- tance through which the effluent must travel to reach an outlet to a maximum of 23 1-2 feet, and in some cases to 17 feet. The underdrains have been laid with the greatest care and are surrounded with layers of gravel of two different sizes; the coarser lying next to the pipe, the finer lying between the coarse gravel and the sand of the filter. By this method of grading, it
3I
is expected that the sand of the filter will be prevented from passing into the underdrains. So large a body of gravel sur- rounding the underdrains will serve as a means of collecting the effluent. The under-drainage system thus provided is one of the most complete which has been provided for any sewage filtration plant, and should result in very efficient work on the part of the filters.
No system of sewage disposal, however carefully designed or thoroughly built, can of itself produce satisfactory results. Much depends upon the operation of the plant, and too great emphasis cannot be placed upon the necessity of securing intelli- gent, careful and constant attention to the disposal plant. If the sludge tank is neglected, the solid matters will find their way onto the surface of the filters with unfortunate results. If the surface of the filters is not properly cleaned, or if the filters are not dosed in rotation, or as their biological condition may require, the results will not be satisfactory. On the other hand, if the plant as constructed had a reasonable amount of care in operation, a very satisfactory result should be obtained.
It may not be out of place in this report, to call attention to the importance of keeping from the beginning accurate and complete records of all changes made in, or additions to the sewerage system, and all work done upon the sewers or upon the disposal plant. A summary of the more important statistics, which should be a matter of record, has been prepared by the Sanitary Section of the Boston Society of Civil Engineers, after a most careful study of the various ploblems involved. The statistics included in this summary should be made a matter of record from year to year, and such other material as may be indicated by your engineer should be collected and recorded from time to time.
In conclusion, I desire to record my belief that through the conscientious work of your engineer and his assistants, and the cooperation of your various contractors in securing good work- manship, you have been able to construct a sewerage system
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and sewerage disposal plant which are not only well designed, . but are thoroughly and well constructed.
I desire also to express my appreciation of the uniformly courteous treatment received at the hands of the Commissioners, and to attest to the ever apparent effort on their part to secure the most economical and best system of sewerage.
Respectfully submitted,
HARRISON P. EDDY.
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REPORT OF ENGINEER LEWIS D. THORPE.
Boston, Mass., Feb. 8, 1908.
To the Sewer Commissioners
of the Town of Norwood.
Gentlemen :-
I submit the following final report upon the construction of the sewer system and sewage disposal plant of the Town of Norwood.
In January, 1907, I was employed by your Board to check over and revise the estimates made by the late Freeman C. Coffin in 1901. In May of the same year I was engaged to design and superintend the construction of that portion of the system known as Proposition No. 3.
ENGINEER'S PRELIMINARY REPORT.
In a report dated April 15, 1901, the late Freeman C. Coffin advised the construction of a separate system of sewers. This system is designed to receive only sewage, other provision being made for the disposal of roof, yard and other surface or ground waters. The system recommended consisted of an outfall or trunk sewer extending from the proposed plant to the northerly part of the town. From this trunk sewer several lines. were to be extended to provide sewerage for the various dis- tricts.
The town is naturally divided into two general sections,. one of which may be sewered by gravity, while the sewage. from the other will require pumping.
The report of the engineer advised that generous provision' be made for the disposal of ground water by the construction of a comparatively large amount of underdrainage, and pointed out the great importance of such construction as would prevent the admission of ground water to the sewer system. The extent to
. 34
which ground water might find its way into the sewer system, and the probable results of careful construction as a means of excluding it from the sewers, were expressed in the following language :
"That it is a matter of importance is shown by the fact that in some systems the flow of ground water alone is 70,000 gal- lons per day per mile of sewers, and that a leakage of 40,000 gallons is not at all uncommon. In fact, there are a number of systems in which the flow of ground water equals that of the sewage.
"It is possible, however, to keep the flow as low as 5000 gallons per mile per day, as shown by recent experience of the works where, under unfavorable conditions, the measured flow of ground water did not exceed 2000 gallons per mile per day. The conditions in Norwood are such that a large flow of ground water may be expected in wet seasons unless the joints of the sewers are well made. In the construction of the sewers, therefore, especial attention should be given to this matter.
The system of sewage disposal recommended, was that known as Intermittent Filtration, which system provided for the filtration of the sewers through natural or artificial sand filters. A tank for the removal of the suspended matter in the sewage and to provide for the proper dosing of the filters, was also recommended.
SEWERAGE SYSTEM AS CONSTRUCTED.
The system of sewers and the sewage disposal plant have been constructed in substantial accordance with the report to which reference has already been made. Some modifications of the details have proved advisable and these will be hereinafter described.
DESCRIPTION OF THE SEWER SYSTEM.
That section of the town which can be drained by gravity is divided into two sections which can be described as follows
35
and referred to as : First, the central district, and second, the Hawes Brook district.
The Central District is enclosed within a line described ap- proximately as follows : Beginning at the Westwood town line east of Nahatan street, and running south across Prospect street, and east of Casey and Myrtle streets, across Washington street, at a point near Philbrick street, thence crossing Pleasant street, at 'a point about 400 feet north of Railroad avenue, crossing Pleasant street again at a point about 400 feet south of Cross street, and continuing across Expensive and Hillside avenues and Willow street to the corner of Dean and Washington streets, thence across the Midland Division of the N. Y. N. H. & H. R. R. at a point near Cedar street, and crossing Walpole street near Chapel street, thence in a northerly direction to the point of beginning.
The Hawes Brook Gravity District comprises an area lying south and west of the following described line : Beginning at a point on Walpole street, near Chapel street, and continuing south to the Midland Division of the N. Y. N. H. & H. R. R. at a point near Cedar street, and then continuing south west along the above named railroad, a distance of about 3000 feet, thence easterly and across Washington and Morse streets, thence south to the Walpole line.
An intercepting sewer is laid in the valley lying between Lenox and Pleasant streets, and running from Willow street to the corner of Williams and Clark streets. This sewer will col- lect the sewage from all of the Central District. The sewage in the Hawes Brook District is collected in an intercepting sewer beginning at the junction of Walpole and Endicott streets, and continuing westerly, and across the Midland Division of the N. Y. N. H. & H. R. R. through the valley, and crossing Washington street, into Morse street, at which point it will dis- charge into a cast iron siphon to be laid in Morse street, and across the Neponset river and the N. Y. N. H: & H. R. R. to a point near Morrill station, thence it will flow in a field line to
36
the 24-inch intercepting sewer leading to the disposal area.
The remainder of the town is divided into two districts from which the sewage must be pumped. One of these called the Pleasant Street District, comprises all of the area north of Hawes brook, and east of the Midland railroad and the intercept- ing sewer of the gravity district, and south of Cross street. The other, called the Purgatory Brook District, lies northeasterly of the Central Gravity District, and north of Cross street. .
It is proposed to collect the sewage from the Pleasant Street pumping District, and discharge it into an under ground reser- voir located at point near the Neponset river, from which it must be pumped to the 16-inch cast iron siphon of the gravity section. The reservoir and pumping station for the Purgatory Brook Dis- trict should be located at a point near Neponset street, between Cross and Pleasant streets, and the sewage pumped through a cast iron pipe to some convenient manhole on the gravity line.
CONSTRUCTION OF THAT PORTION OF THE SEWERAGE SYSTEM KNOWN AS PROPOSITION NO. 3.
During the season of 1907, the filter beds were partially completed and the main or intercepting sewer laid from the fil- ter beds to the junction of Washington and Nahatan streets a distance of 2.14 miles.
The past season, the beds have been completed and about 7.3 miles of sewers laid.
SEWERS NOW LAID.
The total length of sewers now laid, including the main or intercepting sewer, cast iron siphon and 12-inch cast iron pipe in Dean street, is 49,840 feet, or 9.44 miles, the total length of each size being as follows :
6-inch vitrified pipe sewers, S6S2.3 feet
8-inch vitrified pipe sewers, Io-inch vitrified pipe sewers, 7040.7 feet
17,073.8 feet
12-inch vitrified pipe sewers, 3841.5 feet
TOWN OF NORWOOD-DETAILS (
LENGTH AND SIZE (
LOCATION
VITRIFIED PIPE
STREET
FROM
TO
6 in.
8 in.
10 in.
12 in.
15 in.
2
Broadway
East Hoyle
Day
653 3
703.4
4 in.
12 in.
16 in.
6 in
8 in.
0-8 ft.
8 14 ft.
14-20 ft.
20-26 ft.
Total
5
653
704
56.84
89.43
146.27
Day Street
Broadway
Washington
291
358.7
Washington
169.1
Washington
Dosing tank
Pleasant
Willow
Plimpton
Plimpton
R. R. Ave.
158,5
643.4
1172.3
050
5
214.3
9
882
302.62
28.52
Fulton Street
651
1171
341.00
42.99
George Street
Washington
End
284
Washington
Warren
269.9
Broadway
Washington
563.5
2
184
20.11
274
2
570
3.82
1
160
2
589
279.63
10.22
4
1103
432.98
101.60
Maple Street
Cottage
186.1
292.5
Cottage
R. R. Ave.
293.6
228.1
433.3
2
750
Howard
End
329
Cross
R. R. Ave.
2047.8
5
525
430
126.08
131.43
257.51
Nahatan Street
Lenox
Prospect
183.4
2499.6
455
639.4
6
2048
192.56
47.89
290.64
6.97
808
2106
721.75
340.70
29.76
28.62
1120.83
3
500
85
135.05
19.11
1
683
1
462
49.42
18.33
67.75
Railroad Avenue
Market
West End
288.6
2319.2
581.3
2
683
160.08
89.00
249.08
Rock Street
Munroe
Pleasant
330
12
1447
1472
846.91
301.72
4
844
41.40
27.69
9.87
9.87
Washington Street
Douglass
Walpole
701.1
245
588.9
450
7
731
1590
451.81
478.85
930.66
6
483
589
133.10
51.27
184.37
7
1204
887
137.96
349.08
4
337
571
145.90
216.66
362.56
687
1
2
611
50
1603.3
3876.3
159
21072
13106
6618.54
2953.36
29.76
28.62
9630.28
Day
Guild
358
Main Line
Munroe
554.6
3
1043
1
360
2
558
144.46
16.15
Field Line
654
1603 3
3
2
680
13 36
26.85
40.21
83.90
.71
84.61
Nahatan
High
R. R. Ave.
Myrtle
658.8
1
463
15.02
14.93
Granite Street
198.95
33.24
177 32
25.41
202.73
Guild Street Subway
Lenox
Broadway
Fulton
Prospect
End
726.7
371.7
Lenox Street
Nahatan
₭ 11.7
69.4
1237.5
Winter
Washington
464
Fulton
Prospect
746.6
5
1250
148.60
147.68
296.28
Market Street
170.62
62.03
2
163
76.97
6.40
Fulton
End
603
1
79.85
79.85
Nichols Street
Nahatan
Cottage
199.1
Broadway
Central
327.4
Field Line
R. R. Ave.
459
Field Line
Willow
Field Line
Lenox
Nichols
Prospect
1160
2
Railroad Avenue
Pleasant
K Street
816.8
275
5
564
277.70
33.88
311.58
School Street
Nahatan
R. R. Ave.
293
Granite
Philbrick
501.5
69.09
Washington Street
Dean
Culvert
Dean
Douglass
289.8
2023.7
1
205
94.64
7.60
102.24
Washington Street
Nahatan
Philbrick
1575.2
594.7
Walpole
Nahatan
330.6
203.7
Williams Street
Clark
Lenox
410
Willow Street
Pleasant
Winter Street
Broadway
Washington
608.4
TOTAL
8682.3
17073.8 7040 7
3841.5
6266 9
4(
* Stub from Williams Street north.
WERAGE SYSTEM. (TABLE No. 3.)
RS
C. I. PIPE
No. of M. H.
LENGTH OF UNDERDRAINS
CUBIC YARDS ROCK EXCAVATION
Casey Street
Fulton
Prospect
1039.6
Central Street
Cross Street
88.92
113.38
202.30
Dean Street
Pleasant
East Hoyle Street
52.62
47.90
Field Line
33.84
9.09
42.93
Field Line
Munroe
Pleasant
463
475.4
7
2
475
2
333
355.7
High Street
583.8
Howard Street
3.82
Linden Street
289.85
Lydon Street
534.58
1
466
Morse Avenue
232.65
Munroe Street
83.37
Myrtle Street
583
2
240.45
Park Street
297.61
Pleasant Street
Pleasant Street
3.37
154.16 3.37
Prospect Avenue
2975
Warren Street
2
1
561.3
Washington Street
Field Line
487.04
2
410
78.87
56.65
135.52
2
1775.7
1931.3
4
Field Line and Clark St.
Fulton Street
331.14
383.99
29.95
Guild Street
232.19
1
20.11
674.5
Broadway
160.61
100.52
Washington Subway
Nahatan
16
Plimpton Street
1148.63
Washington Street
·
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15-inch vitrified pipe sewers, 6266.9 feet
20-inch vitrified pipe sewers, 404.7 feet
24-inch vitrified pipe sewers, 1050.0 feet
I 2-inch cast iron pipe, 1603.3 feet
16-inch cast iron pipe,
3876.3 feet
Total,
49,839.5 feet
Table No. 3 shows the size and length of sewer, also size and length of underdrain, number of manholes and cubic yards of rock excavation in each street.
UNDERDRAINS.
The amount of underdrainage required has been largely in excess of that estimated, this increase being made necessary by underground conditions that could not be foretold. With few exceptions water was found in the trenches during the dryest part of the season. It was therefore thought advisable, in order to lower the level of the ground water around the sewers, to con- struct underdrains under practically all of the sewers laid.
The underdrains are laid from 12 to 15 inches below the sewers and are embedded in broken stone or screened gravel, thus affording an opportunity for the ground water to enter them and be drained away. Houses having wet cellars can be directly connected to them if necessary. It often happens, however, that the lowering of the ground water due to the construction of un- derdrains relieves the cellars without actual connection with said drains. All the underdrains laid have a free discharge into some brook or waterway, there being five outlets in all. .
The amount of underdrains laid in excess of that estimated has added largely to the cost of the system. In many streets they were laid in rock trenches, necessitating rock excavation, which being generally more than eight feet deep, cost from six to seven dollars per cubic yard. The total length of underdrains laid is 6.567 miles of which 2.83 miles was laid in rock trenches, the total cost of the rock excavated due to the underdrains being $12,820. Adding to this amount the cost of the pipe and laying
38
same, which amounted to $11,504, the total cost of underdrains is found to be $24,325, or $3,704 per mile.
The amount of underdrain estimated in proposition No. 3, was 2. I miles, the estimated cost of which was $5,875. The amount actually laid thus exceeding the estimated amount by 4.467 miles, the extra cost being $18,450.
LEAKAGE.
As the leakage into the sewers must be disposed of as well as the sewage proper, it was desirable to reduce its volume as much as possible. As before stated, water was found in nearly all the trenches during the dryest part of the season and in or- der to reduce its elevation permanent underdrains were con- structed under many of the sewers laid.
Great care was also taken in the design and construction of the sewers to make the joints as nearly tight as possible. By the use of the sand and sulphur joint and by the careful atten- tion given to this work by the inspectors in charge and by faith- ful work on the part of the contractors, this part of the system was made successful beyond our expectation.
The sand and sulphur were mixed in equal parts and heat- ed in a gasoline furnace. It was then run into the joints in the same manner that a cast iron water pipe joint is run with lead. The advantages of the sulphur joint over the cement joint are, first, tightness, and second, that as soon as the joint is run the trench can be entirely backfilled and no further pumping is re- quired.
Another important item in connection with this work was. in thoroughly bedding the pipe in sand or gravel (hauled from the Town gravel pit) when suitable material was not found in that excavated from the trenches.
The total leakage measured before any services were con- nected to the system, was found to be 12,000 gallons per day or 1,500 gallons per mile of sewers. Many systems have been found by careful measurement to have a leakage of ground
39
water to the extent of 40,000 gallons or more per mile per day. On the basis of 40,000 gallons, the total leakage in Norwood would be 320,000 gallons per day or an amount nearly equal to the present total weter consumption of the town.
In this connection it may be of interest to recall the predic- tion in the preliminary report of the engineer, which has al- ready been referred to, that by careful construction the amount of leakage in the sewer system might be reduced to 5,000 gal- lons per mile per day, and in certain cases it has not exceeded 2,000 gallons per mile per day.
It thus appears that the efforts which have been made to exclude ground water have met with success beyond the ex- pectation both of the engineer who made the preliminary re- port and of the engineer in charge of the construction. The very satisfactory results obtained in this respect appear to amply justify the slight expense in the use of sulphur joints, and also the greater expense due to the construction of the extensive sys- tem of underdrains.
CHARACTER OF EXCAVATIONS.
The character of the excavations did not vary greatly from what was anticipated. The excavation in earth would be class- ed as hard digging. For a distance of about one-half mile at the lower end of the trunk line the excavation was through sand and gravel ; beyond this point all the earth excavation required picking.
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