Norwood annual report 1904-1907, Part 12

Author: Norwood (Mass.)
Publication date: 1904
Publisher: The Town
Number of Pages: 1374

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COMBINED FRONTAGE AND AREA PLAN.

From the preceding illustrations it can be seen that the frontage system of assessment favors deep lots and works injus- tice to shallow ones, while that by area favors shallow lots and works injustice to deep ones. A shallow lot is more accessible to a sewer than a deep lot; generally the greater the area of land accessible to the sewer, the greater the benefit. Therefore a combination of the two methods has often been adopted to overcome these difficulties and inequalities. No fixed rule can be made, in sewer assessments, that gives equal justice to all interested, yet a system allowing latitude for the exercise of · individual judgment offers more objection than the injustice of a definite rule.

The question immediately arises as to what proportion of an assessment shall be levied upon the area and what upon the frontage. Generally speaking the greater the area which can be sewered, the greater the benefit, and this has been considered in proportioning assessments by this plan. A common division is to assess six-tenths of the cost upon area and four-tenths upon frontage.

If, then, to illustrate, we take the three lots owned respec- tiely by A, B and C, as shown under the area plan, and assess at the rate of $0.20 per front foot and $0.005 per square foot, the following results will be reached : A, with a frontage of 125 feet and an area of 5,625 square feet, would pay $25.00 and $28.13, a total of $53.13 ; B, whose frontage is only 75 feet but with an area equal to A's, pays $15.00 and $28.13, a total of $43.13; and C, with only 45 feet frontage but whose area is the same as that of A and B, would pay $9.00 and $28.13, a total of but $37.13. However, A can sewer three houses, B two houses, and C but one house, so that whatever advantage C may have in his small assessment, is offset by the increased use to which the land of B and A can be put.

ENTRANCE FEE PLAN.

According to the public statutes, every person who uses main drains or common sewers in any manner shall pay for the permanent privilege to his estate such reasonable sum or sums as the proper authorities shall determine.

This method has been a failure when tried for the fol- lowing reasons-the term "reasonable sum or sums" is indefi- nite and is liable to change with each new board or with the authority upon whom rests the assessment; the financial results have not been satisfactory ; neither the abuttors nor those whose duty it is to levy the assessment have considered it after a fair trial, either equitable or just to either party concerned.

According to the highest legal authority in this Common- wealth, it is the capacity of the land to be benefitted by a drain or sewer that is the subject of taxation. By the entrance fee

plan, the present benefit accruing to a vacant lot is not taken into account, though the owner can sell it at an advanced price because of its proximity to a sewer.

ASSESSMENT BY GENERAL TAXATION AND VALUATION.

Here the question at once arises as to what valuation really is-is it the assessor's valuation, or the price that a piece of property will immediately sell for, or does the valuation depend upon the use to which the property is put? If the first, you can readily see the opportunity offered for dissatisfaction to all parties, in that the assessor's valuation varies from one time to another, according as the board changes or other causes arise, just or unjust, so that an equitable assessment is impossible under these conditions. If based upon the price realized by a forced sale of the property, this valuation will also change from time to time, depending upon various circumstancee, and under ordinary conditions would be very difficult to estimate satis- factorily. Unquestionably the availability of a piece of land for certain purposes affects its valuation, yet the same piece of property may increase or decrease in value during a period of a few years, consequently the rate or amount of assessment would vary constantly, an uncertain and unsatisfactory condition of affairs in sewer assessments.

It is the duty of every owner of an estate to improve and make attractive the surroundings of the home; by this plan of assessment all such improvements are discouraged, as improved land increases in value and the assessment increases propor- tionately.

Again, a piece of cheap land may and often is enhanced in value from its relation to a sewer in far greater proportion than another piece of expensive land highly improved and fully occu- pied. If it be true that a sewer assessment should be based upon the principle of benefits conferred, then valuation cannot be taken as a basis for sewer assessments.

"If an assessment can be levied in direct proportion to the use, then the benefit of a sewer becomes a known quantity ;

there can be no litigation in respect to the uncertainty of this kind of benefit; neither can there be much complication nor confusion."

It is essentially the OCCUPANCY of the land that deter- mines the amount of the benefit conferred from the use of sewers and NOT its valuation.

ASSESSMENTS BASED UPON WATER CONSUMPTION.

"The water that enters homes for domestic purposes is used to cleanse those homes and the people who live in them, also the clothes they wear and the food they eat. In getting rid of the soiled water, which is called 'sewage,' it has been found advantageous to make use of it as a vehicle for removing human excrement and certain other wastes which, because of their character, are easily dissolved and readily held in sus- pension."

A few years ago it became necessary for the town of Nor- wood to secure for its citizens an abundant supply of pure water. The strongest demand for this water supply came natu- rally from those of its citizens who lived in the most thickly settled districts, where cess-pools and privies made it impossible to keep wells and springs in a reasonably pure condition. To- day it is from the users of this water supply in these same dis- tricts that the strongest pressure is exerted in favor of such a system of sewers as will quickly and in a healthful manner remove the sewage from their homes and the grounds about them.

The honesholders' need of a sewer is in direct proportion to the quantity of water which enters the same. The citizens of Norwood consider it just and right that they should each pay for the amount of water consumed in their respective homes ; why, then, should not the amount of sewage that flows from each house that is connected with a sewer be paid for in a simi- lar manner, since it is a benefit directly received ? Experience elsewhere has clearly demonstrated that this method, based as it is upon the principle of "for benefits received," is as just and equitable a plan of assessment as has yet been devised.

It may perhaps be argued by some that assessments thus based would tend to decrease the amount of water used, possibly even to the extent of not sufficiently flushing the sewers to keep them in a proper condition of cleanliness. If a very high rate of charge were to be made, this might possibly be true but where only a portion of the entire cost of the system is to be raised in this manner, it would not apply to any appreciable extent, as has been practically shown wherever this plan has been adopted. It may also be claimed that not all the volume of water, as shown by the meter readings of the Water Depart- ment, finds its way into the sewer, a portion being lost by lawn sprinkling, carriage washing and, in factories and manufactur- ing plants, in steam. Undoubtedly this is true to a certain extent, in the larger manufactories to quite an appreciable extent, but wherever this condition does exist to any marked degree, the sewerage commissioners have the power of remedy- ing it by placing additional meters to register the amount lost through sill-cocks and in other ways and of deducting the amount so lost from the original meter-reading; or in the case of factories a meter or meters may be placed upon the pipe or pipes supplying the sinks and closets and the charge be based upon these readings. For example, if Mr. A was not satisfied with the amount charged him, it would be a simple matter for him, with the approval of the commissioners, to place a meter upon the pipe supplying his carriage house or sill-cocks and deduct the volume so registered from that shown by the water meter. In unmetered buildings, the same basis can be taken , of estimating the volume of sewage discharged into the pipe as is done by the water commissioners, thus it is comparatively easy to regulate the basis of assessment under this plan, al- though of course it greatly simplifies the work of the sewer department if all buildings are metered; this has, in some cities where this plan is in use, been made compulsory.

CONCLUSION.

Having thus somewhat briefly but pertinently discussed the

different methods of sewer assessments in their various phases, it may appear to our citizens that no one system is ideal, or entirely satisfactory to all concerned. Your committee con- siders this to be true and probably no system ever has or ever will be devised without features that will be considered objec- tionable or unjust by some; the aim should be to select that system or combination of systems which offers the least objec- tions and gives the greatest satisfaction to the majority.

In the plan to be recommended for Norwood your commit- tee has chosen what are considered by many practical men con- versant with this subject to be the best features of the several plans, combined in such a manner as to meet the varied conditions and requirements of the situation as presented in Norwood.

After careful investigation, your committee is of the opin- ion that the report made to a previous committee in 1901, by Mr. Freeman C. Coffin of Boston, is substantially correct as regards existing conditions and therefore, we re-submit it to the citizens of the town.

ENGINEER'S REPORT.

BOSTON, April 15, 1901.

Hon. F. A. Fales, Chairman, Dr. E. C. Norton, Mr. W. F. Tilton, Mr. J. F. Callahan, Mr. Waldo H. Bigelow, Secre- tary, Committee on Serverage, Norwood, Mass.

GENTLEMEN :- The following is a report, made in accord- ance with your instructions, upon a system of sewerage and sewage disposal for the town of Norwood, and also upon the surface drainage system of the town.

RECOMMENDATIONS.

After an investigation of the conditions and a study of the subject, I recommend the following :

First, That the "Separate Sewerage System" be adopted and that the surface water be discharged through separate channels into the natural water courses at the nearest available points, substantially as at present.

Second, That the sewage be treated by intermittent sand filtration upon an area lying south of the Neponset River and east of Pleasant Street, as shown upon the general plan of the town accompanying this report.

Third, That the sewage be collected by the lateral main and intercepting sewers, and, with the exception of two low- lying sections of the town, be discharged by gravity upon the filter beds. That the two low-lying sections be provided with collecting reservoirs and pumping machinery, by means of which the sewage will be delivered into the main sewer from the gravity section, and flow with the sewage from that section to the beds.

SYSTEM OF SEWERS.

The sewers are designed to receive the sewage from all buildings, but no roof, yard, cellar, or other surface or ground water. It is economically important when sewage is treated artificially that all surface water (and ground water in as far as it is possible to do so) be excluded. The use of the separate system of sewers in all of the largest cities is now so universal and the desirability of its adoption so well established that it seems unnecessary to discuss it further.

GRAVITY SECTION.

The town is divided in a general way into two sections. One may be called the Gravity Section and comprises all of the area of the town from which the sewage can flow to a filtration area by gravity. There are three separate areas which may be described as follows :

First, all of that portion of the town lying west and south of a line drawn through Morse, Washington, Dean, Willow, Pleasant, Washington, Howard and Prospect Streets.

Second, the area upon the ridge along which Neponset Street runs, and

Thira, a small area about Pleasant and Summer Streets next the Walpole line.

These areas are shown upon the map which accompanies this report.

The first, or larger of these sections, may be again divided into two principal districts, the sewage from which flows to the filtration area through separate main sewers. These two dis- tricts are divided by a line running from the corner of Dean and Washington Streets across the railroad near the foot of Cedar Street, crossing Walpole Street south of Chapel Street, thence northwesterly across Winter Street, about 800 feet west of Prospect Street, to the town line near Nahatan Street, and have approximately equal areas.

The district on the north side of the above line (which may be referred to as CENTRAL DISTRICT) contains about

all of the territory in which sewerage is required at the present time.

The sewage of this district will be collected by an inter- cepting sewer laid from the corner of Clark and Williams Streets through the valley lying between Munroe and Lenox Streets to Dean Street, just east of the Walpole Branch Rail- road, and from this point will flow through a main sewer to be constructed parallel with the railroad across the Neponset River to the filter beds.

The district on the south of the above line, which may be called the Hawes Brook District, has little or no need of sewer- age at present, except to provide for the wastes of Winslow's tannery upon Endicott Street. The sewage from that part of this district which is west of Walpole Street will be collected at the junction of Walpole and Endicott Streets and flow through a main sewer, through the latter street, past the tannery, across the railroad, through the field, crossing Washington Street 350 feet south of Hawes Brook, to Morse Street, thence following Morse Street to a point east of the Walpole Branch Railroad, thence running to the main sewer from the Central District and joining the same at a point near Pleasant Street.

PUMPING SECTIONS.

The remainder of the area of the town is situated at an elevation so low that the sewage from it cannot be delivered by gravity to the filtration area, but must be pumped.

The area from which the sewage must be pumped is also divided into two districts. One of these, which may be desig- nated as the Pleasant Street Pumping District, comprises sub- stantially the area north of Hawes Brook, east of the Midland Railroad, the intercepting sewer of the gravity section, and south of Cross Street.

It is proposed to collect the sewage from this district in an underground reservoir on Pleasant Street near the Neponset River. From this reservoir it will be pumped into the nearest manhole in the main sewer of the gravity system. The pump-

ing station, reservoir and pumping main will be located about as shown on the map. If this section of the sewerage system were to be installed at the present time, the following pumping plant would be recommended :

Two vertical submerged centrifugal pumps, with a capacity of 200 gallons per minute, each driven by a 5 H. P. gasoline or oil engine.

The estimate of cost of this station is based upon the above described plant.

It is not certain, however, that if the construction of this section is postponed for several years, as it seems likely to be, the plant described above will be the most available or economi- cal at that time. The town may then have a municipal light- ing plant, in which case electrically driven pumping machinery may prove to be the best.

At the present time and under the present conditions this plant is recommended as combining the lowest first cost with the least annual expenditure for fuel and attendance.

The pumping for many years to come will probably re- quired but a short time each day, and, as the station is near the filter beds, the man in charge of the latter can operate the pumps. An oil or gas engine does not require a skilled engi- ner. It can be started in a few minutes, and may be left to run without attendance, and stopped automatically. As soon as stopped the consumption of fuel ceases. It is, therefore, a desirable type of power where the amount of work to be done is small and intermittent.

The other low lying district is in the valley of Purgatory Brook and may be called the Purgatory Brook District.

There is little or no need of sewerage in this section at present, and the following plan may be modified by existing conditions when the sewers are constructed. It is proposed to collect the sewage in an underground reservoir on or near Neponset Street at the low point between Pleasant and Cross Streets.

From this reservoir it is proposed to pump it through a

cast iron force main to a manhole in the intercepting sewer of the Gravity Section. The pumping plant may be driven by a gas, gasoline or oil engine, by an electric motor, or that form of power which is most available and economical at the time the works for this section are installed.

The location of the sewer lines, reservoir, pumping station and force main are indicated upon the map.

SEWERS.

The street sewers will be constructed with vitrified clay pipe with "wide and deep sockets." The intercepting and main sewers will be of the same, or, if found to be cheaper, may be constructed of concrete. This can be ascertained when bids are received.

PUMPING MAINS.

The pumping mains which are proposed in the pumping districts will be of coated cast iron water pipe.

INVERTED SIPHON.

There will be but one inverted siphon in the entire system. This will be in Morse Street upon the main line from the Hawes Brook District, where it crosses the valley of the Nepon- set River. It will be laid of coated cast iron water pipe. This inverted siphon is unavoidable. No trouble need be apprehended from it, however, as they are invariably successful when properly laid, and are in common use.

SIZES AND GRADES OF SEWERS.

In a separate system of sewers the flow of sewage in the "laterals," or the sewers which serve only the street in which they are laid, is small, and the size of the sewers is not designed with reference to their capacity to carry the sewage.

Their size is largely fixed by the grade at which they are laid. To secure economy of construction this grade should be approximately the same as that of the street surface. It has been found by experience that it is not advisable to lay any

street sewer smaller than six inches in diameter on account of stoppages, which are more liable to occur in smaller pipes. It is necessary to lay the sewers at so-called self-cleansing grades, that is, at such grades that when flowing half full or more the velocity will be sufficient to carry along any substance which may enter. The method of securing a flow of that volume in lateral sewers will be alluded to under the head of flushing.

In this system no six-inch sewer is proposed where the grade is less than one foot fall in one hundred feet. Where the grade of any sewer is flatter than this, an eight-inch sewer is used, except where the estimated flow is greater than its capacity.

In estimating the amount of the sewage, the future must be considered, as well as the present. As may be inferred from the preceding statement, the lateral sewers will have sufficient capacity for any flow which will come to them when designed to be self-cleansing. In sewers which receive the flow from larger area, however, the AMOUNT of the flow must be carefully considered.

Three elements enter into the consideration of the amount of flow, the population, water supply and leakage into the sewers of ground water.

POPULATION.

The population of Norwood since 1875 has been as follows :

YEAR.

POPULATION.

INCREASE IN

5 YEARS.

INCREASE IN IO YEARS.

1875

1749

1880

2345

34 per cent.

1885

2922

27 per cent.

58 per cent.

1890

3733

25 per cent.

1895

4574

23 per cent.

47 per cent.

1900

5480

20 per cent.

The increase in population in the last two decades has been 58 and 47 per cent, respectively. Mr. X. H. Goodnough, the

Chief Engineer of the Massachusetts State Board of Health in a report in 1897 upon the Discharge of Sewage into Boston Harbor, estimated the future growth of Norwood as follows : YEAR. POPULATION. PERCENTAGE OF INCREASE

IN IO YEARS.

1900

5,540

1910

8,000

44 per cent.

1920

JI,450

43 per cent.

1930

16,250

42 per cent.

1940

22,590

39 per cent.

This estimate is, I believe, as accurate a forecast as can be made of the future population of Norwood.

CONSUMPTION OF WATER.

The average daily consumption of water in Norwood has been as follows since 1886:

YEAR.

TOTAL.

PER CAPITA.

1886

66,600 gallons.

1887

133,000 gallons.

1888

150,000 gallons.

1889 161,000 gallons

1890 169,000 gallons.

1891

178,000 gallons. 46 gallons.

1892

169,000 gallons.

42 gallons.

1893

208,000 gallons.

49 gallons.

1894

220,000 gallons.

50 gallons.

1895

268,000 gallons.

59 gallons.

1896

308,000 gallons.

65 gallons.

1897

354,000 gallons.

72 gallons.

1898

405,000 gallons.

80 gallons.

1899

424,000 gallons.

81 gallons.

1900

400,000 gallons.

73 gallons.

The above is a large and increasing per capita consumption of water. It is possible that it may be reduced, but that this would require some radical change in the policy of the works (such as the general introduction of meters, for instance,) is shown by the history of other works, which, with unchanged

conditions, show a continually increasing per capita con- sumption.

Estimating the future consumption of Norwood from the past it does not seem safe to use a smaller per capita rate than 100 gallons per day for the future.

In estimating the average flow of sewage 100 gallons per day will be taken as the per capita consumption of water, and 75 per cent. of this amount as the proportion of the water supply which will find its way into the sewers.

The flow of sewage is not uniform throughout the day, nor throughout the year by months. It corresponds approxi- mately to the draft from the water supply.

In thirteen cities and towns the average rate of draft in the different months of the year was found to be as follows, calling the average rate for the year 100.

MONTH. PER CENT. OF MONTH. PER CENT. OF AVERAGE RATE. AVERAGE RATE.

January, 87.2 per cent. July, I23 per cent. February, 89 per cent. August, II3.5 per cent. March, 88.6 per cent. September,

109.4 per cent. April, 89.7 per cent. October, IO3 per cent. May, 99.8 per cent.

November, 92.1 per cent.

June,

II4 per cent.

December, 88.7 per cent.

The maximum rate of draft in some water works reaches over 300 per cent. of the average rate for the year for periods of an hour or more at a time. The records of one system that I have studied showed for several days in August that the aver- age rate from 10 A. M. to 3 P. M. was 230 per cent. of the yearly average rate. It is, therefore, probable that the maxi- mum flow of sewage is at least two and one-half times the average flow. That ratio is used in estimating the maximum flow.

To repeat : The basis upon which the estimates of the required capacity of these sewers is made is an average water consumption of 100 gallons per capita, 75 per cent. of which

reaches the sewers, with the maximum flow equal to two and one-half times the average.

GROUND WATER.

The amount of ground water which will find its way into the sewers is dependent upon the nature of the ground and the construction of the sewers.

In clay or impervious ground very little water will come in contact with the sewer, whereas in sandy or gravelly ground, in which the water stands above the level of the sewer, only the best of construction of the joints and manholes will pre- vent large quantities from entering. Freely discharging underdrains will also reduce the amount of ground water enter- ing the sewer.

Careful construction, however, must in the main be relied upon to keep the entrance of ground water within reasonable limits. The economic importance of this matter relates more to the disposal of the sewage than to the size of the sewers, although its effect upon the latter is not unimportant.

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 gallons 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 this 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.

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Norwood annual report 1904-1907, Part 12

Author: Norwood (Mass.) Publication date: 1904 Publisher: The Town Number of Pages: 1374

Author: Norwood (Mass.)
Publication date: 1904
Publisher: The Town
Number of Pages: 1374