1.012 | Spring 2002 | Undergraduate

Introduction to Civil Engineering Design


The Old Charles River Dam

Extracts from:

“Report of the Committee on Charles River Dam … to consider the advisability and feasibility of building a dam across the Charles River at or near Craigie Bridge”, 1903

Necessary Improvements if no Dam is Built

The Charles River, between the Watertown dam and Craigie bridge, has a mean rise and fall of tide of 9.6 feet, with an extreme predicted range of 13.6 feet, which at times of easterly winds and freshet flow of the river may be increased to 15 feet. In case a dam is not built, it will still be necessary, in order to adapt the river to these park requirements, to dredge the unsightly and unsanitary flats in the lower portion of the river basin to a depth of five feet below mean low water. These flats are indicated upon the survey of the basin made under the direction of this committee. The amount and position of the excavations to be made are indicated in the report of the chief engineer, and their extend and appearance at low tide are shown in the accompanying photographs. In addition, certain changes in the sewage from the Stony Brook channels, extending an overflow channel from the Commissioners’ channel to the Charles River, and the interception of the sewage which comes from Beacon Street houses, should be effected; the embankment and walls from West Boston bridge to the westerly line of the Fenway should be built by the board of Park commissioners of Boston, in accordance with the provision of the Acts of 1893, chapter 435, with some amendments hereafter suggested; the unimproved banks of the river above the territory which is to be walled must be dealt with in a similar way to that adopted by the Cambridge and metropolitan park commissions above the Boylston Street bridge; and portions of the tidal marshes should be diked, as has been done by the Metropolitan Park Commission between the Boylston Street and Arsenal Street bridges. As the extreme rise and fall of the tide is about 15 feet, these works will be necessarily expensive. The estimated cost of this work above outlined is $3,914,000.

After this work is completed, however, the river, as a tidal stream, will still for half the thime present an unsightly and unattractive appearance. Its use by the public will be limited, and its possibilities as the main feature of the park system will be only partially utilized.


Sanitary Conditions

The Present Condition of the Basin

In considering the question, the present sanitary condition of the basin must be borne in mind. There are in the basin to-day unsanitary conditions, which must be remedied even if a dam is not built.

The Fenway - The influx of sewage into the Fenway has transformed this body of water from a water park into a drainage canal. The Fens were not offensive as long as Stony Brook discharged through its old channel, in accordance with the original plans of the park department, and the present conditions have been largely caused by the building of the new Commissioners’ channel. The present conditions are a nuisance to the people living in the vicinity, and destroy the usefulness and beauty of the Fens as part of the park system. The objectionable sewage at present entering at various points in both the old and new channels of Stony Brook should be removed. The necessity for immediate relief is fully set forth in the report of the street department, sewer division, of the city of Boston for 1901, in which it is proposed to construct a 12-foot channel from the present Commissioners channel to the Charles River, at an expense of $300,000. While this solution of the difficulty will relieve the Fens, it will transfer the trouble to the river basin at the present outlet of the Fens.

The Main Basin - Direct sewage now enters from the houses on the water side of Beacon Street which should be cut out. There exist in the main basin large areas of flats covered with sewage mud, which are exposed at low tide, and which the Board of Health of the city regard as a “well-recognized public nuisance.” These should all be dredged, if there is to be no dam. There is a discharge of the combined overflow sewage in times of storm from the sewerage systems of Boston and Cambridge by the introduction of the separate sewerage system, already begun in Cambridge and officially recommended by the sewage division of the street department of the city of Boston in its report for 1901. There are numerous breeding-places for mosquitoes which ought to be removed.


Basing its conclusions on the study of these conditions and on the reports of its engineer and special experts, the committee finds as follows: -

Fresh water, gallon for gallon, disposes in a normal manner of more sewage than salt water; the tendency of salt water is rapidly to precipitate sewage in sludge at the bottom.

For the proper disposition of sewage in water, it is essential that the water be well supplied with oxygen. This is accomplished by the contact of its surface with the air, and this surface water is carried down by the action of the waves and currents, and especially by the vertical movement caused by changes of temperature. Bodies of fresh, nearly still water are well oxygenated to a depth of 25 feet or more in ordinary summer weather, and to much greater depths with the autumn cold. No considerable part of the basin, with a permanent level at grade 8 or 9, would be over 25 feet in depth.

Letting in salt water under the fresh interferes with the vertical circulation necessary for oxygenation, and the salt water under the fresh soon loses its oxygen if any waste material is admitted into it.

Changing a fresh water basin into a salt from time to time interferes with the bacterial animal and vegetable growths, which effectively aid in taking care of and digesting sewage.

A comparatively still body of fresh water with animal and plant growths will dispose of a considerable amount of sewage admitted from time to time, and will tend to purify itself, even if no more fresh water is added.

Such a body of fresh water will dispose of more sewage if comparatively still than if in motion.

Most of the sewers in Cambridge and practically all in Boston carry both house sewage and storm water in the same conduits, which are called “combined sewers.” These all connect with the intercepting sewers of the metropolitan system on both sides of the river leading into the lower part of Boston harbor; and in dry weather the metropolitan sewers take all the sewage, none of which goes into the basin with the exception of the sewers to the houses on the water side of Beacon Street, and some emptying into Stony Brook which find their way into the Fenway. The metropolitan sewers are not nearly large enough however, to take both the house sewage and that very much larger body of liquid called the storm water in times of heavy rains and rapidly melting snows; and the surplus of this mixed storm water and house sewage, called the “storm overflow,” is emptied into the basin, excepting when the storm water is small in amount.


Malaria is only spread from person to person by means of the anopheles mosquito. This mosquito breeds only in small pools of fresh or partially salt water; it does not breed in a large basin, with properly constructed shores open to the winds, and supplied with fish, even if the water is fresh. There are now, however, many breeding-places of this mosquito on the borders of and near Charles River, which have been located.

It is not true, as has been contended before the committee, that there is a large inflow into the Charles River basin of salt water direct from the ocean twice every twentyfive hours. A study of the currents shows that the water near Harvard bridge at high tide cannot come from the ocean direct, but at the best from the upper middle harbor as it was at the preceding low tide; and this is made up of what came from the Charles and Mystic rivers with the preceding ebb, mixed with what sea water stayed in the eddies and lagoons or was retained between the wharves from the high tide preceding that. A good deal more of the water making up the body of high tide at Harvard bridge comes from points still less remote. In short, the water in the estuary of the Charles surges back and forth day after day, and only gradually finds its way to the sea; the water at high tide near the Harvard bridge is on the average 8 degrees warmer than at Boston Light; when examined bacterially, it is not superior, if it is equal in purity, to the water at the same place at low tide when there is no sewer overflow going on; it is not as pure as the water coming over the Watertown dam.


The level of the ground water in the Back Bay would not be raised by maintaining the level of the proposed basin at grade 8. The building of a tight wall with an embankment behind it, and the construction of a marginal sewer, emptying at grade 9, below the dam, into which some of the ground water could be drained in the immediate vicinity, would probably enable the basin to be maintained at grade 9, should it prove advisable, without interfering in any way with the ground-water level in the Back Bay. The old mill dam under Beacon Street was practically water-tight, and the ground level beyond it seems to be chiefly controlled by leakage into the sewers.

The combined sewers flowing from the Back Bay and from certain of the lower parts of Cambridge, in case of heavy rains during high tide, back up into and overflow the cellars of the houses to an extent that is a constant menace to the residents. If a permanent grade of 8 or 9 were maintained in the basin, this nuisance and danger to health would be removed.


Commercial Interests

The traffic on the Charles River in the delivery of coal and other material, either to wharves upon the river itself or upon the canals in Cambridge, is one that your committee feels should be preserved, whether this traffic is at present large or small , or whether it is increasing or diminishing.

The construction of a dam with a proper system of locks and with such dredging as is indicated below will, in the judgement of the committee, rather facilitate than hinder this traffic. The formation of ice in the winter will be a possible objection, and an estimate of the probable expenditure necessary to protect the animal traffic has been prepared.

In view of the recommendation of the Craigie bridge as the site of the dam, the committee has considered the need of sufficient room for manoevering vessels between that bridge and the Lowell Railroad freight bridge, immediately below. The evidence submitted to the committee is that a space of 320 feet is necessary, and the committee finds that the requisite space can be obtained by moving the Boston & Maine Railroad freight bridge slightly to the east, and recommends that 400 feet be secured, if practicable.

As the railroad company is under contract with the federal government to renew its present pile bridges with modern structures at an early day, the committee recommends that the railroad be required to locate their new bridges in such a manner as to give the requisite space.

Counsel for property owners on Broad and Lechmere canals have submitted to the committee a stipulation of certain conditions which they regard as essential, with reference to the size of the locks, dredging the canals, the maintenance of the sea-walls on the canals, and maintaining the canals free from ice in the winter. These conditions, so far as they refer to free maintenance of locks large enough to accommodate the largest vessels which will be used on the Charles, and the maintenance of access to the canals free from ice, should be complied with; and, in consideration of the possible future development of commerce, the committee would recommend locks of even greater width than those suggested by the engineers of the proprietors.

The Broad canal is owned by the proprietors of the banks as tenants in common under an agreement dated in 1806, by which they are authorized to maintain a canal at a depth of 9 feet, and they undoubtedly have certain riparian rights of access to tide water. Any act authorizing the building of a dam should contain a provision that the owners of private property on the river above the dam should recover damages for any injury occasioned to their property by reason of the construction of a dam and the consequent reduction of the water level. It is the opinion of the committee, and also of those interested in the river traffic whose testimony is before the committee, that the maintenance or a permanent water level at the elevation of mean high tide would be a material benefit to owners of wharf property above the dam.

If the basin is maintained at grade 8, Boston base, a depth equivalent to the present mean high water can be obtained by a moderate amount of dredging in the canals, and probably with comparatively small expense for strengthening the walls. The walls along these canals were in most cases built about twenty years ago, and in many places are ruinous, and must soon be rebuilt at the owner’s expense. It is probable that the dredging of the canal to the depth called for by the owners at the wharves will result in many cases in causing these walls to fall in. The cost of dredging and rebuilding these walls and dikes, as might be called for under a strict construction of the owners’ demands, is estimated by Mr. Hodgdon to be $331,735. In view of the benefit which these canals will receive by having a constant water level, and of the fact that walls will in many cases require rebuilding at an early date, the committee feels that the stipulation by the owners of these premises, if fully complied with, would place them in a much better position than they now enjoy. Dredging these canals in the manner proposed by Mr. Hodgdon in his report, p. 423, with the riprapping of the slopes, would leave the canals in as serviceable condition as they now are at mean high tides, and this can be done at an expense of $10,000, for work in the canals, which seems to the committee an equitable adjustment of the claim. A moderate amount of additional dredging in the basin would be required. The cost of this would not exceed $25,000. It was stated by counsel for the owners that $80,000 would probably cover the cost of their requirements. An examination of the photographs which accompany this report, showing the condition of these canals at low water, will give some idea of the limitations placed upon commerce in these canals under present tidal conditions.


New Researches and Data Derived from them


(B) Influence of Present Tidal Basin on Temperature of Air - A careful study was made of the influence of the present tidal basin upon the temperature of the surrounding air, both immediately over the water and for some distance back from the Boston and Cambridge shores. Ten self-recording thermometers were stationed at various representative localities, and ten other mercurial thermometers were stationed at other representative localities all the way from Boston Light to Norumbega Park, and read several times daily for a little more than two months. Great care was taken in the calibration of these thermometers, and also in locating them so as to obtain proper exposure.

The result of all these thermometric readings was to show that the basin now cools the temperature of the air on the shores around the basin and at the street level over the middle of the basin by hardly more than a single degree Fahrenheit from 10 A.M. to 4 P.M. on the hottest days; and it is proved by these very numerous and careful observations, beyond the shadow of a doubt, that the apparent coolness of the air on hot summer days near the present basin is almost wholly due to the wind, in very much the same way that the face is cooled by the motion of air from a fan.


(D) Pollution. Chemical Analysis of Water -


The chemist’s conclusions will be found stated in great detail in the appendix devoted to his report. We may summarize the most important of those relating directly to the proposed basin as follows: -

(a) Although there are local pollutions, as a whole, the water of the present Charles basin gets well mixed in going through the bridge piles (soon to be removed), and is found to be fairly clean, with an abundance of free oxygen. The water of the Fens is overburdened with sewage, and its lower strata contain no free oxygen.

(b) Although the upland water, as it enters the basin in time of ordinary low summer flow, is somewhat discolored by dyes and factory washings, it always (except perhaps very rarely in extreme drought) contains an abundance of free oxygen, and it does not contain more organic matter than can be taken care of and rendered innocuous by the proportion of free oxygen contained, and such water if held stagnant in a pond would probably continually improve. This conclusion was reached after many experiments on incubation of this water, etc.

(c) The old and the new Stony Brook conduits continually discharge dilute sewage; Muddy River outlet is at times polluted; there are several places where the water is polluted by factory waste; and in time of storm. considerable amounts of sewage overflow, also much street wash, enter the basin. But if all the pollution now entering were discharged into the nearly stagnant, fresh-water lake produced by the proposed dam, it is doubtful if this pollution would rob its water of all its dissolved oxygen and thereby lead to the generation of the offensive gases of putrefaction. It would probably be absorbed.

This conclusion was reached after an extended series of experiments by incubation of Charles River water containing various percentages of sewage. The chemist confirms this conclusion from a study of the analyses of the polluted Abbajona River water and the bettered condition of this water after storage in Mystic Lake, which was, until recently, used as a portion of Boston’s water supply, and which has recently become a favorite resort for pleasure boating.

The turbidity and pollution from street wash and sewer overflow are now for a time mainly held as a thin layer at the surface, because of this fresh water being so much lighter than the salt, thereby exaggerating the appearance of pollution. With a fresh-water basin the same pollution would be at once more evenly diffused through the depths, and give less apparent defilement to the surface.

In case the proposed dam is to be built, in order to give the surface of the water a more attractive appearance, and a safeguard against offence arising from the fact that the entrance of sewer overflows is intermittent, not uniform, the following improvements are recommended by the chemist: -

(d) The pollution now entering from the Beacon Street houses should be diverted into a sewer. At least a portion of the pollution that now enters the basin through the Stony Brook channels should be excluded, particularly highly putrescent brewery waste. The outlets of polluting material from the abattoir and the starch factory near it should be more efficiently guarded. It is desirable, but not certain, that the dredging of a few of the present sludge banks in the Charles will be reqiured.

(e) Better conditions would prevail for absorbing sewage pollution with the basin filled with still fresh water than if filled with still salt or brackish water. By an extensive series of experiments it is proved that salt water tends to a much greater precipitation of the impurities of sewage in the form of putrefying sludge than fresh water; and numerous other tests show that, when a given percentage of sewage is added to salt and fresh water under similar conditions, offensive odors arise much sooner from the salt water than from the fresh.


(F) Malarial Conditions - The report of investigations relative to malaria, made at your request, form a separate Appendix, No. 1. The pathologist who made these studies has long been celebrated as a most skilful observer in this line of work. His researches for the United States government on the cause of the Texas fever are well known, and his recent call to direct the work of the newly established laboratory in New York for research on contagious disease is a testimonial to the esteem in which his work is held. I am told by competent authority that there is no man in America more competent to pass on these questions of effect of the proposed basin upon the health of the community by promoting or retarding conditions favorable to malaria. It is, therefore, most reassuring to learn that, following years of study on the origin of malaria, and after having repeatedly explored all parts of the adjacent territory, devoting a large part of his summer to this study, he reports: -

(a) “It is quite firmly established that the micro-organism of malaria which produces the well-known disturbances in the body by multiplying in the red blood corpuscles is transferred … by a certain species of mosquito.”

(b) “The malarial microbe is a true parasite in all its stages. It never exists free in the air or in the water or on vegetation, but spends its life partly in the blood of man, partly in the organs of the mosquito.”

(c) ‘‘All shallow pools in which water may stand for a portion of the year, and which are cut off from the permanent bodies of water so small fish cannot enter, may become breeding-places of mosquitoes, and should be filled up."

(d) “As regards the river itself, we may safely assume that the proposed basin will not become a breeding place for mosquitoes,’’ if so treated as to contain abundant fish life, and if its banks are so treated as not to afford protection for mosquito larvae from their natural enemies, the small fishes.

(e) Impurity or pollution of water, as in the present Fens basin, if made fresh water instead of salt, would tend to restrict the natural enemies of the mosquito, the little fishes, and, by greatly favoring the growth of fresh-water algae, might eventually lead to the multiplication of culex and anopheles mosquitoes. “This necessarily implies the removal of all sewage from the Fens basin.”

(f) “In reviewing all the conditions likely to prevail in the future in and about the Charles River basin, there seem to be none which would tend to the increase of malaria provided the suggestions made are carried out. In fact, the improvement of the banks and the territory beyond them would be a great improvement on present conditions, and tend to relieve those near the marshes of all mosquitoes now breeding in these places, and perhaps remove the causes of malaria prevailing at the present time, unless such malaria is due to bodies of fresh water beyond the immediate confines of the proposed basin.”

(g) “Fresh water v. salt. The substitution of a fresh-water basin for the present tidal reservoir would not tend to intensify malarial influences, providing the present breeding-places of mosquitoes are properly dealt with. There would be a material improvement over present conditions, both as regards mosquitoes and malaria.”





The only important disadvantages that would result from this dam appear to be: -

First - The extra cost (if any) of the dam and its auxiliary structures above the cost of the structures that will be required for sanitary and other reasons, if no dam be built.
(It appears that, taking account of the present condition of Craigie Bridge the dredging of foul mud banks; the improvement of the Fens required regardless of the dam; the necessity for filling and diking and draining marshes; the absolute necessity of improving the dirty banks of the upper portions of the estuary, the method of improvement by means of the dam and its auxiliary structures will cost the least of any efficient method of treatment that can be devised.)

Second - The loss of interest involved in an earlier expenditure for the separation of sewage from storm water than would otherwise be demanded.
(It does not appear that any part of the cost of remedying the present unsatisfactory conditions front sewage in the Fens basin or of removing the defilement from the two Stony Brook channels is properly chargeable to the dam. Neither should the cost of a sewer for the Beacon Street houses be charged against it, nor the connection to sewers of sundry privies and stable drains, now emptying openly or leaching into the basin and the Cambridge canals. The work of separation of sewage from storm water was begun in Cambridge two years ago and, the report of the Boston sewer division for the year 1901 strongly recommends that a similar work be begun in Boston, purely on sanitary and economic grounds, almost without regard to the Charles basin. This work of improving the sewers of Boston and Cambridge must be done sooner or later, although no dam be built. The building of the dam will merely stimulate an earlier and more energetic carrying out of the work.)

Third - The greater interference to navigation by ice on a fresh-water basin, in comparison with the present salt-water basin, and possibly, rarely, some increased trouble with ice in the part of the harbor near the railroad bridges below the dam.

Fourth - The compensation of damages that will doubtless be asked for by those owning wharves.

Fifth - Some very small increase in the cost of dredging out certain deposits of gravel for purpose of sale. (This will be far more than offset to the owners by the market afforded for this gravel in the dam.)

Sixth - A very small increase in total amount to be pumped at the pumping stations of the Boston main drainage and the metropolitan sewerage, due to the larger average quantity of storm water that will be stored in the main sewers after that lying below grade 8 can no longer drain into the Charles at low tide, and must, therefore, drain down through the regulator gates into the metropolitan sewers after the storm is over, and immediately be pumped.
I have had a very complete estimate made of this possible storage in the Cambridge system connected with Binney Street, the largest system of all, and find this will involve only a comparatively insignificant expense.

Seventh - The need and cost of flushing the Broad and Lechmere canals. (This has been provided for by means hereinafter described, and, in this respect, the arrangements proposed in connection with the dam will relieve the present unsatisfactory dirty condition of the Broad canal, due to oil sleeks on the basin that come from gas works and from asphalt roofers’ waste, and that which comes from storm wash of streets and dirty yards.)

Eight - The need and cost of special means for circulation in the Fens basin, now produced by the tide. (This can be done better than now by the marginal conduits elsewhere described in this report. Much less circulation will be required than now, after the “foul flow” of Stony Brook is removed from the Fens by the connection of the new “commissioners’ channel” with the old 7-foot channel.)

II. Full Dam v. Half-tide Dam

I have given careful consideration to this because of the plan having been favored by certain men whose opinions are entitled to great respect. I have come to the opinion that the improvements which are most desirable can be accomplished very much better by a dam of full height than by a half-tide dam. It appears that much more than half of the advantages for pleasure boating and for park development, with neat, attrac-tive water margins, free from wetness, slime and mud, pos-sessed by a basin with slight current, at constant water level, would be sacrificed by a half-tide dam. For half the time the objectionable current would be as strong as now. For half the time the upper half of the slope would be as unsightly as now, and there are some dangers to life connected with pleasure boating controlled by a half-tide dam, due to boys in boats or canoes coming too near the overfall, or to direct attempts to run the rapids while fall was moderate.

The benefits of the constant water level near grade 8.0 or 9.0 in preventing the flooding of the marshes, in draining the mosquito-breeding pools and in lessening the height of storm discharge from sewers and drains would be wholly sacrificed by a half-tide dam. The Back Bay cellars and Cambridge cellars would continue to be flooded by the backing up of sewage in severe storms at high tide, just the same as now. A half-tide dam would not properly cover the broad areas of objectionable mud flats in Watertown (see map of upper basin) and, indeed, the rise of the tide, as now, to grade 10.4 (saying nothing about the frequent rise to about grade 12, Boston base) would keep these marshes, guzzles and shores wet and slimy; and its fall to grade 5.2 would uncover many acres of slimy, muddy slopes and flats, mainly in Brighton, Cambridge, Watertown and Newton.

Indeed, so far as now seen, the only substantial advantage presented by a half-tide dam is: -

  1. It would secure the covering of the mud flats near Harvard bridge and the dirty strips of flats exposed at low water along the present embankment walls.
  2. It would prevent uncovering the unsightly, bad-smelling bottom at the upper ends of the Broad canal and the Lechmere canal.
  3. The daily flushing of the Charles basin with salt water would have nearly the same effect as now, and permit the separation of storm water from sewage to make slower progress, and permit delay in providing a sewer for the houses on the north side of Beacon Street.
  4. It would afford to the shipping the same flood tide depths as now, during the week of spring tides, and would prevent some of the grounding with the ebb tide that now occurs.

In brief, it would deprive Newton, Watertown and upper Cambridge of the benefits that it brought to Boston and Cambridge port.