USA > Massachusetts > Bristol County > Attleboro > Reports of town officers of the town of Attleborough 1894 > Part 11
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ANNUAL REPORT.
work has greatly exceeded our first anticipations, yet a careful con - sideration of the plans readily shows why the cost will be so large. "Unfortunately for this work the town is so flat and has so little fall from the upper to the lower end of the village that in order to have suffici - ent fall in the sewers to properly convey the sewage it will be necess- ary for the sewers at the lower part of the village to ba several feet below the level of the water in the river and Dodgeville poud. As these sewers will probably be in quicksand it is evident that their cost will undoubtedly be heavy.
This matter has received the care'ul attention of our engineer an 1 advantage has been taken of every possible means of reducing the cost of these main sewers We believe the arrangement or the piping for the sewerage system, as shown on the plans and profiles is the one that must be adopted for delivering the sewage at the proposed loca- tion of thepumping station by gravity. This system also provides for under-drains wherever they are needed to assist in lowering the level of the ground water.
Having delivered the sewage at the lower end of the main sawers, it will be necessary to then pump it as the sewers will be too low to discharge by gravity at any location where it would be advisable to discharge the sewage. This will of course add to the first cost, the cost of maintenance of this pumping station. From this point the sewage can be delivered by the pumps to the most favorable location for treatment. Two methods of treatment are feasible in our case either chemical precipitation or intermittent filtration through sand or gravel. Of these Mr. Coffin recommends intermittent filtration as being less expensive for maintenance and giving better purification of the seawge
This method of treating sewage has been used but little in this Country up to the present time and probably in but few places outside of Massachusetts. It was first used in Massachusetts at Lenox in 1876. At Amherst it was introduced in 1881. At Medfield in 1886 and since that time works for the disposal of town sewage by inter mittent filtration have been built by the towns of Framingham, Marl - borough, Gardner and Westborough. The city of Brockton is at present constructing works of this kind which are nearly completed- Within the last few years an experimental statiou has been operated at Lawrence under the direction of the State Board of Health where extensive experiments are being made which extend over a term of several years with a view to determining the conditions and method of treatment under which the best results can be obtained. The re- sults already obtained by these towns, and at the experimental station indicate that a high degree of purification can be obtained by this
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ANNUAL REPORT.
method under the proper conditions, and it is probable that the result of further experiments by the State Board of Health in the next few years will determine with greater certainty what method of arrange- mere of filter beds is best with the different kinds of sand or gravel to be found in different locations, and also the best method of applying the sewage to the beds.
In conclusion we wish to submit the follhwing recommendations :-
I Before the town can issus bonds sufficient to raise a sum that will build any considerable portion of this system of sewers, it will be necessary to obtain authority of the legislature to exceed the debt limit as fixed by statutory law. Therefore we recommend that before the town undertakes to build any portion of this system that a bill be carefully drawn and submitted to the legislature that shall contain, besides a clause authorizing the issue of the necessary amount of bonds, all the essential features of similar acts recently enacted for other towns and cities that have adopted and built large systems of
II That wherever the grade of the proposed sewers require that the grade of the surface of the street be raised above its present grade the town adopt the grade indicated on the profile as the permanent grade of such streets. There are but few places where the grade of the streets are thus changed but the town should adopt the proposed grade at as early a date as possible in order to avoid any damage that might result in case improvements should be made on the property abutting these streets which would suffer injury by a change of grade at some later time.
Ill That the town take action to secure the land and rights of way that will be necessary for the proposed location of the system of sewers in so far as it is possible and advisable without legislative act- ion.
IV That before entering upon the work of constructing this sys- tem of se wers a thorough investigation be made of the plan of assess- ing betterments in connection with the building of the sewers and some plau adopted. Without some such plan the town cannot at present afford to undertake the work, audit the system is to be built under the betterment plan it will be advisable to have that plan thoroughly understood andagreed upon before the actual work of construction begins.
Finally we earnestly recommend that every citizen make a careful study of the report of our engineer. The report deals in a most thorough manner with a subject that vitally affects the welfare of the entire community and one that calls for careful consideration by every one.
Respectfully submitted,
E. S. HORTON, GEO. A. ADAMS, NAHUM PERRY, JAS. W. GIFFORD, A. B. CARPENTER, JOHN THACHER, WM. J. LUTHER.
'To EVERETT S. HORTON, JAMES W. GIFFORD, JOHN THACHER, GEORGE A. ADAMS, WM. J. LUTHER, NAHUM PERRY, ARTHUR B. CARPENTER, L-
Committee on Sewerage.
ATTLEBOROUGH, Mass.
GENTLEMEN :-
In compliance with your request as expressed in a letter from the secretary of your committee July 25, 1894, I herewith submit my report upon a system of Sewerage with plans and estimates, for the town of Attleborough, Mass.
DATA.
The data from which these preliminary plans have been prepared. was furnished by you, in the shape of profiles of streets from the- town records and in the case of new streets by level notes and a plan. furnished by you, compiled from the above sources, and such addi- tional measurements as were necessary. It is probable that the plan and profiles are approximately correct, but no doubt in data compiled in this way there will be minor discrepancies in distance, and more over the manholes at changes of line and street intersections have no. been located on the ground, therefore the exact distances between the manholes cannot be known at present, and are not given on the pro- files in figures, but the manholes are located upon the profile as. clearly as possible leaving the matter of exact location to be made at the time of construction. The only difference that this will make- will be in the total rise or fall of the sewer between the manholes, which will be a small matter on the flatter grades, as for instance the difference of even five feet in the distance between two manholes,. would be an inclination of 1 to 100 make but .05 of a foot difference. in the elevation of the sewer. In all manholes that occur at a change of grade or entrance of a side sewer, I have allowed a drop in the. grade of the sewer of .01 foot or more, so that I believe there will be no practical difficulty from this source. Of course in steep grades. there is no trouble in overcoming any variation of this kind.
In doing the work in this way you have made a great saving in ex - pense for surveys as you had so much of the data on hand, and I do- not hesitate to say that the work of construction can be as satisfac torily done, if the work of laying out each street or line is done be
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ANNUAL REPORT.
fore any pipe is laid in such street or line, and checked with the pro- file, this should be done in any case.
GENERAL DIVISION OF THE SUBJECT.
In the discussion of the subject it naturally falls into the following divisions :
1. The kind of system to be adopted.
a. The combined system taking sewage, roof and surface- water.
b. The separate system taking only the sewage.
c. The separate system modified by the admission of roof or cellar water.
2. System of Disposal.
a. Natural into river or sea.
b. Artificial by precipitation, irrigation or filtration.
3. Street sewers.
Size, velocity, inclination, manhole, material.
4. Flushing.
5. Underdrainage.
6 Pumping.
SYSTEM TO BE ADOPTED.
A system of sewerage is commonly understood to be a system by means of which the waste from houses, stores, shops, etc., are carried by the water used in the various processes of modern life to some point where it will not cause a nuisance and in some cases it is combined with the same system that provides for the surface water, then it is called a "combined" system and in others only the sewage is admitted, and the. rain or surface water otherwise provided for. This is known as the "Separate" system.
Each system has its advantages and its advocates for large cities. with many paved streets and much roof surface, and few natural un- polluted water courses, but the general opinion of engineers, and the great bulk of modern practice is in favor of the Separate System for- smaller cities and towns where the natural water courses can carry off the surface flow with little expense for drains. This system is- recommended for your town without further discussion except to allude to the large sewer necessary to carry the water in time of heavy storms, in the Combined system and through which in dry weather, a. slight stream of sewage trickles along, leaving here and there in its slow progress accumulation of filth to decompose until the next storm washes them away.
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ANNUAL REPORT.
DISPOSAL.
Perhaps the most important question to be decided in a sewerage system. and the one often requiring the most study is that of the dis- posal of the sewage. Natural disposal will be first considered for Attleboro, and this may be divided into disposal into the sea aud into river and water courses. By natural disposal is meant simply carry- ing by gravity to some point and there discharging it without treat- ment. In a town situated near the sea we naturally turn to that first. It would probably be a physical possibility for Attleboro to discharge its sewage into the sea or one of its arms, but in making this inquiry we are at once met with the fact that the city of Providence, after long and careful investigation, finds it more desirable or economical to discharge its sewage at Fields Point, only after an expensive treat. ment by Chemical Precipitation than to carry it out to sea where it might be discharged in a crude state. This would seem to be con- clusive evidence that Attleboro could not afford to carry its newage to such a point. Neither is it to be supposed that it would be allowed to discharge at Field's Point or above without previous treatment. As an examination of the map will show, Narragansett Bay is the only place for disposal by gravitation into salt water.
Has Attleboro any river or water courses into which it can turn its crude sewage ?
The physical conditions would probably allow of its being dis- charged at some point below Hebronville into the Ten Mile River, but as this point would be less than ten miles above the place where East Providence takes its water supply from the same river, this plan is forbidden by statute. As this exhausts all the possibilities for natural disposal of the sewage of Attleboro we must look to some plan for artificial disposal.
ARTIFICIAL DISPOSAL.
For artificial disposal there are in general three methods with their modifications viz:
Chemical Precipitation.
Irrigation.
Filtration.
CHEMICAL PRECIPITATION.
Chemical precipitation will be discussed uo further than to compare its cost, both first and annual with that of filtration, in case it is found possible to use the latter. Stated in a broad manner the cost of the tanks, building and machinery for the chemical treatment of
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ANNUAL REPORT.
sewage will be quite equal to the cost of filter beds if a favorable loca- tion for the economical construction of such beds can be found.
The pumping station and pumping machinery, if pumping is re- quired, will be about the same in one case as the other.
The attendance required for the precipitation plaut for Attleboro would certainly exceed that for the filter beds by not less than $1000 per year. The only i em of expeuse upon the filtration system that would exceed the other, would be the laud required for the filtration area and the force main from the pumping station to the filter field .
The cost of chemical precipitation would be approximately 20 cents per annum per inhabitant as shown by the report of the State Board of Health.
Assuming 8000 inhabitants this would be
Per annum
$1600.00
Increased cost of attendance
1000.00
Total annual expense over filtration
$2600.00
To offset this would be the interest on the excess of first cost of filtration over precipita ion. This difference is estimated at not to exceed twenty thousand dollars ($20,000.) the interest upon which at four per cent. (4 per cent. ) equals eight hundred dollars ($800.) Difference in annual maintenance including interest on first cost equals twenty six hundred dollars ($2,600) less eight hundred dollars ($800.) which is eight en hundred dollars ($1,800.) in favor of filtra- tion.
Besides the financial side of the question, the effluent from chemical precipitation contains about twenty times as much pollution as that from the filtration plant when both are working at highest rate of efficiency and in a form that is liable to cause a greater nuisance than the latter.
IRRIGATION.
Irrigation has few if any advantages over filtration, the greatest, perhaps, is that land that can not be used for filtration or used only a t great expense for preparation can be used for irrigation, but to offset this, it requires very much more land for the latter. Another argu- ment that has been used in its favor, is that it may be financially profitable and return in the way of crops some of the expense of maintenance.
Whether this would be the case or not depends largely upon the conditions in each case and upon the management. There is one difficulty met with, and that is, that the best method of handling the sewage for complete purification, sometimes conflicts with the best
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ANNUAL REPORT.
. treatment of the land for the profitable raising of crops, as in a wet time the latter are better off without the sewage. There have been columes written on both sides of the subject. The practical outcome of it seems to be that there are in this country few if any successful sewage farms. It is not recommended in your case if land can be found suitable for filtration.
FILTRATION.
By filtration is usually meant intermittent downward filtration through beds of sand or gravel, either in a natural state or artificially constructed with or without underdrains. Where a sufficient area of suitable land can be found, this is an economical and efficient means of purifying sewage to such an extent that the effluent can be turned into a water course without creating a nuisance. Filter beds of this description are in use in Framingham, Marlborough, and Gardner in this state where an affluent is obtained, the average of the analyses of which show a removal of from 91 to 99 per cent. of the impurities as indicated by the reduction of the albuminoid ammonia. The city of Brockton has recently constructed a system of this kind, which is not yet in operation, aud in the report of the city engineer is much value able information relating to the subject. The State Board of Health of Mass. has been for several years past conducting an extensive series of experiments upon sewage filtration and in its report is to be found most valuable information upon the subject and great aid to the desigu of efficient filter beds. There is in Attleboro, in the southerly portion of the town, a large tract of land that seems to be well suited to the purpose of filtration. This land lies on both sides of Tiffany Street and westerly from the Ten Mile River as shown on the map accompanying this report. There are approximately forty acres suitable for this use.
Mechanical Composition of material found at Tiffany street filter field and their value for filters :
Test pits were sunk at various locations in the proposed filter field and a sufficient number of samples of the material found at various depths have been taken to give an accurate idea of the quality of the materials in this location and its distribution.
Of these samples a number sufficient to cover the entire range of materials found, from the finest to the coarsest, have been analyzed (mechanically) and the results are shown in the accompanying dia- gram of " Mechanical Composition of Materials." The scales used in this diagram are the same as used in the report of the State Board of Health for 1891, p. 430.
MECHANICAL COMPOSITION OF MATERIALS AT
FILTER FIELD, ATTLEBORO, MASS.
100
No. 18
90
-
No. 10
No. 6
No.22
No. 8
No.//
80
No. 19
Per Cent by Weight
60
50
40
30
20
Fine
Coarse
10
o
.01
.03 .06 .12 .24 .46 .98: 2.20
6.20 12.60
Diameter in Millimeters
FREEMAN C. COFFIN,
Civil and Hydraulic Engineer, 53 State Street, Boston.
December, 1894.
· Analysis made by State Board of Health.
NOTE .- Numbers on curves indicate number of Test Pit.
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ANNUAL REPORT.
By comparing the composition of materials from the proposed filter beds as shown by this diagram, with the composition of materialg. used in the filter tanks at the experimental station of the State Board of Health, as shown in the diagram of the report referred to above, an approximate idea can be formed of the value of these materials for the purpose of filter beds.
For the purposes of comparisons we will consider the quality of the material at this location as consisting of two classes.
CLASS I. Having an effective size of 0 204 to 0 479 millimeter.
CLASS II. Having an effective size of 0.074 to 0 105 millimeter.
Class I. includes by far the greater area and comprises all the land north and south of Tiffany Street, the surface of which has an elevation higher than grade 396.
Class II. is found on a limited area in the southeasterly part of the proposed filter field and is found in the form of a stratum of about a foot in thinkness directly under the subsoil and underlaid with material similar to Class I. extending to ground water.
The following table furnishes a comparison of the effective size of materials used in some of the filter fields where filtration of sewage has been carried on successfully on a large scale.
LOCATION.
EFFECTIVE SIZE OF MATERIAL.
Marlborough, Mass.
0.12 to 0.14 millimeter.
Gardner,
0.10 to 0 24
0.32 to 0 42
Framingham,
" Class I.
0 204 to 0 479 66
Attleboro, 66
II. 0.074 to 0105
It will be noticed that Class I corresponds more nearly with the size of material used at Framingham. This is certainly a favorable indication as the results obtained at Framingham have been very satisfactory, and while these results have been rendered possible by other favorable conditions (such as a considerable depth to the ground water, large area of land in use in proportion to the amount of sewaga treated, and high temperature of the sewage in winter owing to the fact that the water supply is taken from the ground, all of which con_ ditions can be approximated in Attleboro), yet it is probable that the size of the filtering material contributes greatly to the successful results obtained.
It is proposed to bring to the sewage in a cast iron force main from the pumping station to the filter beds by the way of South Main Street and Tiffany Street. This main to be fourteen inches in
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ANNUAL REPORT.
diameter. From this force main the sewage can be delivered upon any of the beds.
No plans of filter beds have been made at this time, as this is a matter that will require a good deal of investigation and numerous. test pits to be dug, which, as a portion of the land is under cultivation, would be objectionable to the owner. In a general way I should ad- vise that the best and highest portion of the area be used first and perhaps treated in an experimental manner, for instance a few beda might be graded, and a large area used without grading. I would also suggest that a few beds be made in the higher portions in the coarser materials, and so underdrained that the effluent or the larger portion of it could flow on to lower beds and be filtered again, the idea being to run comparatively large amounts of sewage to the acre upon the higher beds, using them as a kind of strainer and then filter tha effluent more slowly on a larger area on the lower beds. The area on which the finer material is located might be used for secondary beds. Something of this sort has been done with very good results at the Lawrence experimental station of the State Board of Health, then a current of air was drawn through the first beds. This would hardly be practicable on a large scale, but there the filtration was very rapid and perhaps wi h slower filtration very good results might be obtained without the artificial aeration.
It would be advisable to acquire all of the available land in the vicinity, and at first the area used could be large as compared with the quantity of sewage, but with little expense for construction of beds, later as the quantity to be treated increases, more expense could be put into construction and the sewage filtered at a higher rate of speed per acre. With beds properly prepared and of suitable mate- rial it is possible to treat the sewage of one thousand people per acre.
I am of the opinion that with the strainer beds suggested above, a settling tank and sludge beds would be unnecessary.
SEWERS.
Before designing the lateral and intercepting sewer it is necessary to decide whether or not the roof water or the water from the cellars is to be admitted. As all the sewage will have to be pumped and treated on the filter beds it would be advisable in your case to admit nothing but the sewage. The system has been designed upon this basis.
No sewer less than six inches in diameter is designed for any street and none less than eight inches where the inclination is less than one in one hundred. Where the quantity of sewage required larger sew- ers they are designed to care for the sewage of from twenty to fifty
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ANNUAL REPORT.
persons per acre on the territory to be served in different portions of the town using a water supply of one hundred gallons per head per day and 75 per cent of it used in twelve hours of the day which is approximately the rate of the use of the water supply.
The sewers are designed of such a size that they shall run one-half full under the above conditions. This will give a margin for larger quantities of sewage for a short time and for a larger population upon the territory. A circular sewer running one half full flows withthe same velocity as when running full, and discharges one half the sew- age and is self-cleansing at the same grade.
When running full or half full the sewers in this system are de- signed to have the following minimum velocities :
6 inch sewers 3 1-2 feet per second.
3 and in a few street s 2.1.2.
.8 “ 10 6 1-2 12 4 2 1-4 to 21-2 15 and 18 inch sewers 2 1.2
Your town is rather level and much study was required to secure grades that would give the above velocities, and some deep cutting is also necessary. The topography of the town divides it into four main divisions or sections which may be designated as follows :
1 Thacher Brook Section.
2 Ten Mile Rivar Section.
3 South Main Street Section.
4 County Streat Section.
Thacher Brook Section includes practically al of the area east of the N. Y., N. H. & H. R. R., on which the surface drainage is into Thacher Brook, and Hope, Benefit, and Oak Streets on the west of the railroad.
The sewers of this section will discharge into an intercepting sewer located along the line of said brook, and to be within the limits of the proposed improvement of the brook. This intercepting sewer runs from Forest Street to the side of the proposed pumping station and is about fifteen or sixteen feet below the present surface.
Ten Mile River Section includes about all of the area west of the railroad and north of County Street. The sewers of this section dis- charge into a low lying intercepting sewer running from the inter- section of West Street and North Avenue in the general direction of the Ten Mile River to a point on said river about opposite Manches- ter Street where it unites with the sewer from County Street Section ..
South Main Street Section comprises all of the area between the railroad and the divide between Thacher Brook and Ten Mile River, and the sewers discharge into the main sewer in South Main Street.
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ANNUAL REPORT.
County Street Section is the territory in and around County Street west of the summits at the intersection of Third and County Streets.
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