THE MIAMI CONSERVANCY DISTRICT
EDWARD A. DEEDS, Dayton, Chairman
HENRY M. ALLEN, Troy
GORDON S. RENTSCHLER, Hamilton
Board of Directors
EZRA M. KUHNS, Secretary
OREN BRITT BROWN, Attorney
JOHN A. McMAHON, Counsel
CHAS. H. PAUL, Chief Engineer
This Booklet compiled by C. N. PHILLIPS, Office Engineer
THE STORY OF THE
MIAMI CONSERVANCY DISTRICT
THE DISTRICT: The Miami Conservancy District is a political subdivision of the State of Ohio established June 28, 1915, under the provisions of the Conservancy Act of Ohio. The District exists for the purpose of building and maintaining flood control works in the Miami Valley. It includes portions of nine counties, namely: Montgomery, Shelby, Miami, Clarke, Greene, Warren, Preble, Butler, and Hamilton. The power to organize a District is vested in a court made up of one common pleas judge from each county. The executive direction is in the hands of three directors, appointed by this court and reporting to it. The directors in turn employed a secretary, an engineering and construction organization, sold bonds to provide the necessary funds, and proceeded to build the works, now rapidly nearing completion.
THE MIAMI RIVER AND ITS VALLEY: The Miami River drains the southwestern portion of the state of Ohio. Its source is in Logan County, just west of the center of the state, and it empties into the Ohio River at Cleves, a few miles below Hamilton. The total length of its winding course is 163 miles. Its most important tributary, the Whitewater, empties so near the mouth of the Miami, that it is not commonly considered a part of the Miami River system. The important tributaries of the Miami above Hamilton are Four Mile, Seven Mile, Twin, and Wolf Creeks, the Stillwater River and Loramie Creek from the West, and the Mad River from the east. Wolf Creek and Stillwater and Mad Rivers join the Miami in the city of Dayton. The Miami drainage area is about 120 miles long. Its area above Hamilton is 3,672 square miles and above Dayton, 2,600 square miles. The slopes are short and steep, the grades of the main streams rather flat. While draining of swamp lands, tiling, cultivation of farms, and possibly the destruction of the forests have slightly increased the flood runoff, the tremendous floods that sweep down the valley are due primarily to the great storms which occur at intervals in this section of the United States.
First settled about 1790, the Miami Valley has grown to be a prosperous community with numerous busy towns and rich farmlands. The towns have, in general, grown up along the streams and the old Miami and Erie Canal, which were the first means of transportation, and consequently these towns are in the overflow channel of the river in many cases. The history of the valley is replete with accounts of serious floods, culminating in the great disaster of 1913. In the past, more or less inadequate levees have been built around the towns, but until after the flood of 1913, no comprehensive plan for making the valley safe had ever been adopted.
THE 1913 DISASTER: From Sunday, March 23, 1913, until Thursday, March 27th, the Miami Valley was swept by a tremendous storm. The streams of the valley, fed by the steady downpour, rapidly rose and overtopped the levees. Tuesday, Wednesday, and Thursday the waters raced through the city streets. The water was twelve feet deep on Main Street in Dayton. Thousands of people were marooned for three days and nights in the attics and on the roofs of their dwellings. Over 400 lives were lost, $100,000,000 of property wiped out, and the communities of the valley were prostrate as a result of the calamity. The detailed story of the disaster is told in Part I of the Technical Reports published by the District entitled The Miami Valley and the 1913 Flood.
AFTER THE FLOOD: With great determination the citizens accepted both their individual and community losses, cleaned up the wreckage, and re-established their businesses. Martial law was declared, and the militia patrolled the streets of the towns, and enforced order. Every able-bodied man was put to work. Food was distributed and tents supplied to the homeless and telegraph lines, wrecked by the flood waters, were rebuilt and communication restored. Business men arranged for credits so that normal business could be resumed. Strengthened by disaster and self-sacrifice, the communities emerged from the wreckage with an added vigor and courage which has been reflected in the wonderful progress the valley has made since 1913.
FIRST STEPS IN FLOOD PREVENTION. Before the wreckage was cleaned from the streets, the citizens, with the same courage and determination that marked the rehabilitation of their personal affairs, faced the problem of preventing the reoccurrence of such a calamity. Acting through the several Citizens’ Relief Committees, funds were raised, and engineers employed to study the problem. Within sixty days after the flood Dayton alone raised a fund of two million dollars, twenty-three thousand individuals contributing. The Dayton Committee first employed the Morgan Engineering Company of Memphis to work out a plan for flood prevention for Dayton. As the investigations progressed it became apparent that the difficulties in securing a satisfactory solution to the big problem were so great that the cooperative action of the entire valley was necessary. The retarding basin-channel improvement plan developed into the most satisfactory comprehensive plan for the protection of the entire valley, and was adopted as the Official Plan of the District.
THE CONSERVANCY LAW, THE FORMATION OF THE DISTRICT, AND THE LEGAL STEPS LEADING UP TO CONSTRUCTION: Ohio did not have a law that would permit a great co-operative undertaking of this nature. Consequently the Conservancy Act of Ohio was prepared, and passed by the Legislature, February 18, 1914. The day after the signing of the Conservancy Act by the Governor a petition was filed in the court of common pleas of Montgomery County, asking for the establishment of the Miami Conservancy District. Then followed a legal battle on the constitutionality of the law, and it was not until June 28, 1915, that the District was established by the Court, and the directors selected. The appraisers were appointed on August 4th. On November 25, 1916, the Official Plan, a combination of channel improvement and retarding basins, was approved by the Court. The appraisal roll was filed May 19, 1917. On September 1,1917, the directors of the District levied an assessment on property in the District; on September 13th, they advertised the construction work; on December 3rd, they sold the first installment of bonds, amounting to $15,000,000; and on the last date they decided to handle the construction work with forces employed directly by the District, the bids submitted by contractors being unsatisfactory. A construction organization was then built up, equipment purchased, and on January 1, 1918, the construction period started. The history of the steps leading up to construction is told in detail in Part 2 of the Technical Reports, History of the Miami Flood Control Project, published by the District. The “Contract Forms and Specifications” and “Atlas of Selected Contract and Information Drawings”, under which the works have been built, have been published as Part 6 of the Technical Reports.
THE OFFICIAL PLAN FOR FLOOD PROTECTION: The Official Plan was determined upon only after many schemes had been studied and discarded as not practicable, or as too expensive. The diversion of Mad River into the Little Miami, the building of bypasses for carrying the water around the cities, channel improvement by itself, and a system of many small retarding basins, were among the schemes that were found undesirable. After the present retarding basin-channel improvement plan was decided upon, much thought was given to the possibility of combining flood prevention and power development; but it was not found possible or practicable to make this combination in the Miami Valley. It was found that the use of the Miami Conservancy District dams for power development would not be advisable from a financial or practical standpoint.
The first step in preparing the plan was to survey the job. All the recorded floods were studied, rainfall records collected, the 1913 flood discharges carefully calculated, the probable frequency of floods determined, the capacities of the present channels computed, foreign flood prevention plans reviewed, flood and rainfall records in other watersheds compared with the Miami, and miscellaneous other matters investigated. Part 4, Calculations of Flow in Open Channels; Part 5, Storm Rainfall of the Eastern United States, and Part 8, Rainfall and Runoff in the Miami Valley, of the Technical Reports published by the District, cover the details of the studies. A flood 40 percent greater than that of 1913 was decided upon as the maximum to be taken care of by the flood prevention works.
During a large flood, many times the amount of water the normal river channels will carry, must be taken care of. The Official Plan provides five basins formed by building across the valleys five earth dams of the safest and most desirable type. Substantial concrete outlets, founded on rock and passing through the base of each dam, permit the ordinary river flow to pass unobstructed. The sizes of the outlets are such that at times of highest floods, only such amounts of water will escape below the dams. The excess water is held back by the dams and accumulates temporarily in the valley lands situated above them, to flow off later through the outlets as the floods subside. Except during floods, which usually occur in January, February, and March, the valley lands composing the bottoms of the basins are in their normal condition and can be used for crop growing. They will, in fact, be improved by the flooding, since the deposit of rich silt carried by the streams during high water will increase their fertility. Buildings are to be removed from the areas that may be flooded by the dams. Storage is provided for a total of 847,000 acre feet of water under maximum flooding conditions.
Although it scarcely seems possible that a flood more than 40 percent larger than 1913 can occur, spillways are provided at all of the dams in order to keep the water level from reaching the tops of the dams should such a flood come.
It was evident that the capacities of the basins could not be developed beyond certain physical limits without excessive cost imposed by the presence of towns and railroads, also that channel improvement was feasible and economical to a limited extent. Thus, by trying many different combinations of channel improvements and retarding basins, a combination of size of storage and capacity of channel was found that would give the required protection at the lowest cost. As the channel improvements are only in the cities, it follows that the lands outside of the cities are only partially protected. The extra cost of fully protecting these lands would greatly exceed the benefits resulting therefrom. Part 7 of the Technical Reports published by the District, Hydraulics of the Miami Flood Control Project, gives an orderly presentation of the methods followed in determining the type of the flood control plans and of the methods of working out their application.
Four railroad lines, several telegraph and telephone lines, and many highways occupied rights of way in the basin areas. In the case of the railway lines, the rights of way were within the areas in which the dams are built. These public utilities are now relocated on higher ground, wholly or partially out of reach of the backwater from the retarding basins.
The Official Plan was carefully worked out in detail before it was presented to the Court. A list of the lands effected was also given. Every citizen was given the opportunity of ascertaining just how his business or his property would be effected by the proposed works and given the opportunity of objecting, if he so desired.
WHERE THE MONEY COMES FROM: Legally, the Conservancy District, under the provisions of the Conservancy Act, is a public corporation, armed with all necessary powers to levy taxes, borrow money, condemn land, or to do whatever may be necessary to the accomplishment of the flood prevention work. In August, 1915, the three appraisers appointed by the Conservancy Court, began to determine for all real property and for the communities as a whole, the benefits which will result from the construction of the flood prevention works. About one half of the total benefits were assessed to the cities and counties as a whole. These are in proportion to the degree a flood equal to that of 1913, would affect them as communities. The other half of the benefits were assessed to the individual pieces of property subject to actual flooding. The value of the property, degree of protection needed and provided, depth of flooding in the 1913 flood, were all considered in arriving at the result. In order that the assessment would be equitable, property affected similarly by flooding was assessed like proportions of their values. For instance, all the properties having ten foot depths of water over the first floor in 1913 were considered as benefited by the same percentage of their appraised value, and similarly for the other depths of flooding. About 60,000 pieces of property belonging to nearly 40,000 different owners were appraised. When the benefits were added up they totaled $77,000,000 in round numbers.
The construction is being paid for from the proceeds of the sale of $33,890,909.83 worth of bonds, secured by the benefits appraised and representing approximately 50 per cent of the total benefits. The bonds will be retired by 1949, a portion being taken up each year. The money to take up the bonds, to pay the interest on the bonds, and to pay for the maintenance of the works, will be provided by a tax against the benefited property. Since about one half of the total benefits were assessed against the cities and counties of the District, about one-half of the yearly tax is levied against all of the property in the cities and counties. The other half is levied against the properties protected against actual flooding in proportion to their benefits.
In addition to the establishment of the benefits, the damages caused by the proposed works were set by the appraisal board. Rights of way were obtained, and the rights to flood the lands in the retarding basins were secured. As these lands are still available for agriculture, a portion of the land owners elected to sell a flood easement to the District. Others, uncertain as to the effect of the basins on their property, sold their holdings outright to the District. About 30,000 acres were so purchased. These lands are being resold with a flood easement attached.
THE SIZE OF THE JOB: The decision of the directors to construct the works with the District’s own forces instead of letting contracts, necessitated a different kind of organization than a purely engineering staff, and greatly increased the number of problems to be met.
The actual work consisted of the construction of five dams, levee and channel improvements at nine villages and towns, the relocation of four railroad lines and of many highways and wire lines, the elimination or removal of one village, the lowering of water and gas mains, and many minor pieces of work. The quantities of materials involved were large. Some of the major items are as follows:
Public Service Relocations:
2,500,000 cubic yards excavation
30,000 cubic yards concrete
55 miles railroad track
Flood Prevention Works:
250,000 cubic yards concrete
18,817,000 cubic yards earth and rock
The concrete if put into a road would make a 16-foot concrete highway from Cincinnati to Toledo. The earth moved, if put into ordinary two-horse dirt wagons drawn by teams, spaced far enough apart to allow the teams to walk, would fill a string of wagons long enough to go around the world six times. To move such an outfit would take almost twice the number of horses and mules existing in the United States.
MEN AND ORGANIZATION: An organization of men to do the job was the first need. The engineering side of the house was ready, but the construction side had to be gotten together and whipped into shape during the winter of 1917-1918. As far as possible local men were selected, but since suitable skilled superintendents and men were not always available locally, some men were obtained from remote parts of the country. Not only were men to do the actual digging needed, but accountants, storekeepers, cooks, buyers, warehouse men, chauffeurs, skilled mechanics on repair work, and many others had to be secured. The District early adopted a definite labor policy that guaranteed fair treatment. The organization was ready when the frost got out of the ground in 1918. Despite the war, and the attraction of easy jobs at big pay that existed at every hand, the construction force loyally stuck to the job, and has brought it to within sight of the end. At no time did the District suffer seriously for lack of men. The maximum number employed at any one time was 2,000 and the minimum 750.
THE EQUIPMENT: Tools to work with were the second need. The job called for 21 draglines, 29 locomotives, 200 cars, 63 automobiles, many miles of railroad track, over 100 pumps, over one hundred transformers, 73 miles of transmission lines, five camp villages comprising 230 major buildings and 200 sheds and other outbuildings, with running water and baths in dwellings and bunkhouses, construction buildings, 5 mess halls, 5 stores, and 1800 other pieces of equipment, besides many small tools. Although considerable part of this had to be assembled and erected on the ground before dirt could be moved, the work was started March 1, 1918.
SUPPLIES: Material and supplies were the third requisite. The widely diversified construction program called for an amazing variety of articles. Seven thousand, eight hundred car-load lots, and several thousand less-than-car-load lots, have been received. The car load shipments would make a solid string of cars reaching from Cincinnati to Dayton. Some of the principal items have been 450,000 barrels of cement, 70,000 tons of coal, 10,000,000 feet of lumber and 400,000 gallons of gasoline. The total spent for materials and supplies, not including construction plant, has been about $6,000,0000. The purchasing, distributing, and accounting of these articles has been a job of no mean size.
BUILDING THE DAMS: The dams are five in number, namely, Germantown on Twin Creek, protecting Middletown and Hamilton; Englewood on the Stillwater, Taylorsville on the Miami, and Huffman on the Mad, all just above Dayton, and protecting Dayton and the towns below; and finally Lockington on Loramie Creek, a tributary of the Miami above Piqua, built for the special purpose of protecting Piqua and Troy, although of course, it protects the towns below as well. The dams are all built of earth, by the hydraulic method, and are all pierced by concrete conduits, which carry the normal stream flow through the embankment. The principles of construction are identical in all of them, with but minor differences in the handling of the material.
The principal dimensions of the dams are given in the following table:
Germantown Englewood Lockington Taylorsville Huffman
Dam Dam Dam Dam Dam
Volume earthwork cubic yards…. 800,000 3,600,000 970,000 1,130,000 1,350,000
Maximum height, feet………….. 110 125 78 78 73
Length feet………………………. 1,200 4,700 6,400 3,000 3,300
Maximum thickness at base, feet.. 655 785 415 415 380
Volume concrete work, cubic yds. 17,400 26,500 32,000 48,000 37,500
Railroad sidings on which to receive and unload freight; houses, dormitories, and messes for sheltering and feeding the workman; transmission lines over which to transport electrical energy, and erection of equipment were undertaken first. As the progress on construction of the dams depended upon the promptness with which the streams were diverted through the permanent conduits, those structures were started at the earliest possible moment. The conduits are founded on rocks. Considerable work was necessary in order to remove the overburden of earth and to excavate into the solid rock beneath, for the foundation, and for the stilling pools at the outlet ends of the conduits. At Lockington, rock was near the surface of the ground, so that relatively little work was necessary. At Taylorsville over 700,000 cubic yards of earth and rock had to be hauled out to make way for the concrete.
Two types of outlet structures were used. In the first, the conduits and spillways are separate structures, while in the second they are combined in one structure. At Germantown and Englewood, where the first type was used, twin tunnels were placed at the elevation of the old river bed, and extended through the base of the dam from toe to toe. In order to provide sufficient capacity to safely take care of moderate floods during construction, these conduits were made deeper than required ultimately, the enlarged capacity being maintained during the construction period. As soon as the dam embankment reached such a height that there was no further danger of its being overtopped by floods, the bottoms of the tunnels were filled in and floored over with a massive slab of concrete, leaving the openings of the size required for permanent flood control. At Englewood the spillway is at the west end of the dam, while at Germantown it is in a saddle in the hills at some distance from the dam.
The other type of outlet structure, which was used a the Lockington, Taylorsville, and Huffman Dams, was first built virtually as a gap, or great trough, through the dam from toe to toe, formed by two massive walls of concrete facing each other with a concrete floor between. This gap through the dam gave ample waterway for the passage of floods of considerable size, during the construction period. After the dam embankment had been raised to the elevation where there was not further danger of overtopping by floods, a concrete cross dam was built between the two side walls of the outlet structure, leaving openings, or conduits, at the bottom of such size as is required for permanent flood control. The tops of the cross dam, which constitute the spillways, are from 12 to 15 feet below the tops of the earth embankments.
The spillway question was a vexing one. The “forty per cent greater flood than 1913,” for which the entire project is designed, will only bring the water up to the elevation of the top of the spillways, and will not put water through them. The studies made and the history of floods in the past all indicate that this “forty percent greater” flood is larger than actually can occur. It is very probable that the spillways will never be used. Considerable thought was given to a plan which omitted them, but it was decided that the dams would not contain that absolute element of safety that was promised the people of the valley, unless these safety valves were included in the design. They are built as strongly as if a torrent of water were expected to go through them every year, and as they stand are ready for instant service.
As highways cross the valleys on top of the dams, the spillways are all spanned by substantial concrete bridges, strong enough to allow two twenty-ton trucks to pass each other (trucks twice as large as any now permitted by state laws.)
During flood stages, with the basins nearly filled, the water will emerge from the conduit tunnels with high velocity. To break up this velocity a carefully designed structure built to utilize the hydraulic jump, is placed at the lower end of the conduits. The hydraulic jump uses up energy when the water lifts itself in the standing wave, and the attendant pools also use up energy when the water swirls about within them. The water leaves the lower end of the structure quietly, with low velocity. The experiments leading up to the adoption of this design, and the theory of the hydraulic jump, are discussed in detail in Part 3 of the Technical Reports published by the District, entitled Theory of the Hydraulic Jump and the Backwater Curves.
Excavation for the outlet structures was performed by dragline machines. A large part of it had to be first loosened by blasting. The vertical sides of the rock excavation were trimmed down to the final lines by hand, and the concrete laid directly against the rough rock, thus forming a tight bond between the two.
Gravel suitable for concrete was found close at hand, and in one case (Lockington) enough was excavated in uncovering the rock foundation to furnish all the concrete material needed. The natural gravel was excavated by dragline, and brought to a gravel plant close to the site of the work, where it was dumped into a hopper, elevated by a belt conveyor to the top of the plant, then washed by water under pressure, and separated into three sizes, sand, fine gravel, and coarse gravel. Excess and oversize material was discarded. The proper proportion of material was delivered to a one-yard concrete mixer in the same building. Cement came from a shed close at hand. The resulting concrete was delivered to the site of the work by narrow gauge trains operated by gasoline locomotives, and either “chuted” into place, or hoisted in buckets by means of steel derricks, as the location permitted. The mix of concrete varied from about 1-13/4-3 ½ in conduit linings to about 1-3-6 in the bodies of the heavy retaining walls. Collapsible sectional forms were used in the tunnel type of outlet structure, while movable panel forms were used in the other type, and in the spillways. Wherever possible, equipment and forms were standardized. The cement and concrete were under the control of chemical and physical tests at all times.
In constructing the earth embankments, stream control during construction was an important factor. While the conduits, as first constructed, could take care of moderate floods, the menace of another 1913 flood was ever present. The dams are so large that they could not be built in one season, between flood periods. It was very desirable that the work on them be started before the conduits were finished. The procedure at Englewood well illustrates the methods used to accomplish the ends desired, and to meet the flood danger.
While the conduits were being constructed on the west bank of the river a section of the earth embankment, containing something over one million cubic yards, was constructed on the east bank, using a cross dam along the river bank to hold the semi-fluid hydraulic core in place. The old river channel remained open through he winter of 1919-1920, so as to take care of the possible extraordinary flood contingency. After the acute flood season of 1920 was passed, another section of the embankment, containing another million yards, was placed across the old river channel, and over the conduits, and a temporary spillway was closed, the dam finished to its full height, the conduits reduced to their normal size, and the dam made ready to safely handle any flood that might come along. A similar procedure, varying somewhat with the local condition, was gone through with at each dam, care being taken that the critical periods, that is, the closure of the river channels, should not occur simultaneously at any two of the dams.
The hydraulic fill method owes its origin to placer mining. It was first developed in the West, where it became well known and much used long before it was introduced into the Middle West and the East. Where materials are suitable, as they are at the Miami Valley dam sites, and proper methods are employed, a very satisfactory dam is produced. It is made up of an impervious clay and silt core in the center of the dam, running unbroken from top to bottom, held in place by massive banks of sand, gravel and boulders. For instance, at the bottom of the Englewood embankment the core is 125 feet thick, and the banks on each side 330 feet thick; half way up, the core is 62 feet thick, and the banks each 156 feet thick; at spillway elevation the core is 16 feet thick, and the banks each 39 feet thick.
In the hydraulic method, the natural borrow pit materials are thoroughly broken up by water and are carried by moving water, either under pressure in pipes, or in open sluices built on a steep grade so as to give the stream of water a high velocity, to the outside edges of the embankment under construction, where the water with its burdens of material is dumped on the outside edge. The water, released from pressure, flows towards the center of the dam over the sloping banks by gravity. The heaviest material carried (rock) drops out of the stream first, as the velocity decreases, then the coarse gravel, then the sand, until when the central portion, or core, is reached, only the fine material is being carried along by the water. A pool of still water, somewhat wider than the core, is maintained in the center. When the water flowing over the beaches on each side hits this dead water the last remaining velocity is taken out of it, and the fine material still being carried is deposited in the central section. This fine material is semi-liquid mud just below the water line of the pool, but at greater depths it soon loses all the characteristics of a fluid, and becomes a solid dense mass, through which water will not percolate. The water level in the pool is controlled by a drain at one end, which draws off the surplus water from the top of the pond. The dam is built up in layers of only a few feet in thickness, the central pool being carried up with it. The hydraulic method utilizes natural methods, and produces a dam as solid and free from settlement as the very hills themselves, and a good deal more water-tight than some of them.
At the five dams built by the District the mixed materials from the river bottom were well suited to the hydraulic process. The location of the borrow pits, in most cases below the top of the dam, forced the use of dredge pumps and pressure pipe lines to lift the water and its burden of material up into the dam.
The machine most generally used in breaking up the borrow pit material and thoroughly incorporating it with water is the hydraulic giant. It looks like a cannon, and shoots a two to five inch stream of water under heavy pressure. At Lockington and Taylorsville the topography of the ground made it possible to mount the giants in the borrow pits, to tear down the hillsides with the powerful streams, and to transport the water and material through open sluices to the dredge pumps, where it was picked up, and forced under pressure through 15-inch pipe lines, up into the dam. At the other places it was necessary to excavate the material by dragline, load it into standard gauge 12-yard dump cars, haul it by locomotives to a central point and dump it into a shallow pit, known, for want of a better name, as a “hog box.” In this box the hydraulic giants played their streams upon the earth dumped from the cars, broke it up, and pushed it to a sump at one side of the hog box, where the dredge pumps picked it up and delivered it as at the other dams.
The rate of progress made, varied with the equipment used. Day and night shifts were employed at all of the dams. At. Germantown, with one dragline machine in the borrow pit, and one dredge pump, an average month’s work was 60,000 to 70,000 cubic yards, while the largest month’s work was 91,500 cubic yards. At. Taylorsville, with four giants in the borrow pits, and two dredge pumps, the highest monthly output was 107,000 cubic yards. At Englewood, with three dragline machines in the borrow pits, and two dredge pumps, the monthly record of hydraulic fill often reached 150,000 cubic yards, and during one month it amounted to 180,000 cubic yards.
The use of dredge pumps made it impossible to transport boulders larger than 6 inches in diameter, as nothing larger would go through the pumps satisfactorily. This prevented the placing of a blanket of big stone on the outer slopes, as is often done on hydraulic dams. Since there is danger of the rainfall washing gullies in the gravel slopes as they now stand, vines and grasses are being planted to prevent erosion, although the lack of soil makes it a difficult job to get plants to grow on the slopes.
It can readily be appreciated that the mixture put through the pumps and pipes, would wear them out very rapidly. In the course of the work special shells for the 15-inch centrifugal dredge pumps, made in some cases of manganese steel, and in others, of white iron, were developed. Removable manganese shoes were used on the runner blades. Special dredge pipe of high carbon and manganese steel, electrically welded, was also developed. These features greatly increased the life of both pumps and pipe, and kept down the cost, as well as expedited the work.
MOVING THE RAILROADS: The land now included within the Huffman Basin was traversed by the Big Four, Erie, and Ohio Electric Railways; while the land within the Taylorsville Basin was traversed by the Baltimore and Ohio. Not only was it necessary to move these lines in the basins to higher elevations to avoid flooding by backwater during floods, but also to get them out of the way of the dams themselves. It was necessary to start the relocations at the north end of Dayton in order to secure length enough to climb to a sufficient elevation by the time the dams were reached without exceeding the ruling grades. Fifty-five miles of track was involved. The changes were made at the expense of the District, under general directions of the railroad companies. It was necessary in every case to complete the new lines, ready for traffic, before the old lines could be abandoned. The old lines then became the property of the district, the rail and ties being salvaged for what they would bring.
CHANNEL IMPROVEMENT: As explained in the paragraph entitled The Official Plan for Flood Protection, channel improvement is an essential part of the scheme. By removing bars and islands and by deepening, widening, or straightening channels, much was gained at moderate expense. At Dayton, however, the numerous concrete bridges, and the valuable property adjacent to the river, placed a very definite limit to channel enlargement. The same condition existed at Hamilton, save that at one point a considerable enlargement of the channel, which had been severely encroached upon by industrial plants, was absolutely necessary, although it involved heavy expense.
Three general methods of channel improvement were required. First, that in which channel excavation is the most prominent feature and levee raising is a minor item, as at Hamilton and Dayton; second, that in which the work is confined almost entirely to levee construction, as at West Carrollton, Miamisburg, Franklin, and Middletown; and third, a combination of these two features, as at Troy and Piqua. Cutoff channels helped the situation, also, at Troy and at Middletown. Clearing out trees and other obstructions was worth while in several places.
In the first method, having determined upon the channel capacity and size, the problem was to build a uniform channel section on a uniform grade, so as to give uniform velocities of flow, or as nearly uniform as conditions permitted. Changes in velocity are undesirable since they cause increased losses of heads, and make for the formation of bars and islands. Thus it was necessary to actually narrow up the old channel at certain points in order to prevent changes in velocity. The standard improved channel section at Dayton and Hamilton has a low water channel about 150 feet wide, with flat slopes of beaches on either side, extending out to the toes of the levees. The low water channel is located in the center of the river, where the latter is straight, and near the outside of the bends, where the channel is curved. The levees are parallel to each other, and of equal height. As the improvements on the channel in most cases will result in increased velocities of flow, concrete revetment is used at critical points to protect the banks. Elsewhere sod is employed. Concrete walls were built at narrow places in order to get the required waterway without encroaching on valuable property, as, for example between Third and Fifth Streets in Dayton.
The second and third methods require little explanation. To protect by a levee simply means building a wall of earth high enough and strong enough to hold out the water.
The presence of the Miami and Erie canal,city sewers, and power canals at various places complicated matters. In general they are taken care of by building flood gates where the levees cross them. These flood gates remain open at ordinary stages, but are closed when flood waters threaten to enter through the canal openings, or back up through the sewers.
The dragline excavator was the principal piece of excavating equipment used. In removing material from the river, several methods were used. At most of the towns material to build the levees could be obtained by excavating in the river channel, or in borrow pits using a dragline with a long boom, and depositing the dirt directly into the levees. At other points the draggling could not reach far enough in one turn, or “throw,” so cast the dirt in a long windrow as far over as it could, and picked it up a second, or even a third time, finally depositing it in the levee.
At Dayton and Hamilton, however, the channel excavation was so much in excess of levee requirements that a large portion of the excavated material had to be disposed of in waste banks. A part of this was deposited directly by the draglines, but most of it was located in parts of town where the land adjacent to the levees was of such value as to preclude its use as a waste bank. It was necessary, therefore, to transport this extra material by some means. At Hamilton the nature of the channel was such that a construction track could be built within the river channel but high enough above the normal water surface to be out of danger from moderate floods. The waste material, therefore, was loaded into 12-yard dump cars, and hauled off to the waste banks by means of 40-ton standard gauge locomotives. This method was also possible at the lower end of the work at Dayton across the river at the mouth of Wolf Creek, sufficient in height to give backwater deep enough to float scows and a steamboat. It was even found practicable for a certain portion of the work to mount one of the large draglines on a scow and take out some of the excavation with this floating equipment. The scows, loaded by draglines, were towed away to the waste banks by the tug, where they were unloaded by another dragline.
Every town had its special problem. Sometimes contracts were let for small portions of specialized work. Sections could occasionally be built by teams to advantage. Water and gas mains had to be lowered. Bridges had to be raised and lengthened, and even moved. At two towns new bridges were called for as an extra feature, the town themselves paying the extra cost.
The limits of this article prevent the inclusion of many interesting features. Indeed, such a bird’s eye view as the above, can only give the prosaic outline, and must, perforce, omit the details, which are by far the most interesting part of the picture. The handling, housing and feeding of the men, the endless experiments that were made to speed up and cheapen the work, the story of how this or that particular difficult job was accomplished, the social significance of this great co-operative enterprise, are all worthy of individual stories. Many of them have been already told in the Conservancy Bulletins, and in the technical reports.
The schedule of work, as laid down at the start of the construction period, called for the completion of the last dam on June 1, 1923. Despite delays due to moving the railroad lines, the last dam was completed on December 31, 1921, thus giving the valley protection against a 1913 flood a year ahead of time. Some work of planting slopes and graveling roads remains to be done this spring. Considerable work remains to be done during the summer of 1922 on the various channel improvements. The work already done in the town, with the help of the dams, will take care of a 1913 flood; protection against a 40 percent greater flood will be an accomplished fact in the fall of 1922. Whenever the hour of danger comes again, and it will surely come, perhaps tomorrow, perhaps a century hence, the dams and levees will be ready, for they have been built for all time.