Publications of the University of Texas Publications Committee: F. W. GRAFF R. H. GRIFFITH G. C. BUTTE J. L. HENDERSON D. B. CASTEEL E. J. MATHEWS FREDERIC DUNCALF C. E. ROWE The University publishes bulletins six times a month, so numbered that the first two digits of the number show the year of issue ; the last two the position in the yearly series. (For example, No.1701 is the first bulletin of the year 1917.) These comprise the official publications of the University, publications on humanistic and scientific subjects, bulletins prepared by the Department of Extension and by the Bureau of Municipal Research and Reference, and other bulletins of general educational interest. With the exception of special numbers, any bulletin will be sent to a citizen of Texas free on request. All communications about Univer­sity publications should be addressed to the Chairman of the Publications Committee, University of Texas, Austin. 446-2282-919-!m University of Texas Bulletin No. 1922: April 15, 1919 ROADS AND PAVEMENTS Papen Presented Before the Short Course in Highway Engineering Held at the University of Texas, March 31-April 12, 1919, Under the Auspices of the Departmentof Engineering PUBLISHED BY THE UNIVERSITY SIX TIMBS A MONTH, AND ENTERED Al SBCOND-CLASS MATTER AT THE POSTOFFICE AT AUSTIN, TEXAS, UNDER THE ACT OF AUGUST 24, 1'12 The hene&t. of education and of aaeful lmowledse. senerau,. clilfaaed tlaroqta a community, are •seatial to tile preservation of a fr-pYel'll• meat. Sam Houston Culti...ated mind is the s•rcliaa senius of democrac,.. , . . It is the onl,. dictator that fr-men ac:lmowl· edce aad the onl,. security that free· men desire. Mirabeau B. Lamar CONTENTS PAGE Earth Roads. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 R. G. TYLER, Adjunct Professor -of Highway and Sanitary Engineering. The Preparation of Road Plans Involving State or Fed­eral Aid........................................ 15 M. C. WELBORN, Road Engineer, State Highway Department. Drainage Areas and Culverts. . . . . . . . . . . . . . . . . . . . . . . 22 G. G. WICKLINE, Bridge Engineer, State Highway Department. Preparation of Specifications and Contracts. . . . . . . . . 28 R. G. TYLER, Adjunct Professor of Highway and Sanitary Engineering. Road Surfaces. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 J. D. FAUNTLEROY, District Engineer, Bureau of Public Roads. Bituminated Roads. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 M. C. WELBORN, Road Engineer, State Highway Department. Penetration Bituminous Pavements.. . . . . . . . . . . . . . . . . 53 R. G. TYLER, Adjunct Professor of Highway and Sanitary Engineering. Trap Rock as the Mineral Aggregate in Hard-Surfaced Roads and Streets. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 A. H. Mum and E. L. DENNIS, JR., of the Texas Trap Rock Company. Concrete Construction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 JULiAN MONTGOMERY, Division Engineer, State Highway Department. ROADS AND PAVEMENTS EARTH ROADS BY R. G. TYLER Adjunct Professor of Highway and Sanitary Engineering It will be many years before even the majority of the highways of Texas are improved by the construction of a permanent road surface, and it is necessary, therefore, to consider at the beginning of this short course in Highway Engineering the subject of the construction and mainte­nance of earth roads. Every engineer in charge of work for a county or a road district will have, in addition to his duties of constructing permanent road surfaces, a con­siderable amount of work to do with the ordinary earth highway. The importance of this subject, then, is due to the very large comparative mileage of this type of road at present in use. Below is given the mileage of the various classes of road surfaces in Texas as obtained from the State Highway Department, and is as nearly accurate as any information available on this subject at the present time. From this, it will be seen that 85 per cent of the roads of Texas are earth roads. An engineer, therefore, who is un­informed on this class of construction is poorly equipped to practice his profession under existing conditions. Total miles of read in Texas . ..... ..... ....... 148,000 Earth roads ............. ........... .........126,000 Sand-clay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12,818 Gravel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7,325 Shell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . J,138 Bituminous surfaced . . . . . . . . . . . . . . . . . . . . . . . . . 395 Macadam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276 Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Wood-block . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . 2 Brick . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . 0.33 An earth road is a very desirable type of road so long as it is dry. It is usually quite smooth, and, except with certain classes of soil, may not be extremely dusty. It is to be preferred for horse-drawn traffic to the harder road surface during suitable weather conditions. Its disadvan­tages are principally due to the effect of wet weather, when it is practically impassable. A further disadvantage lies in the excessive cost of proper maintenance. There are certain preliminary investigations which should be undertaken before locating an earth road, and these same investigations should, of course, be considered in questions of relocation. Since the location of a road of any kind is one of the permanent f ea tures of its construction, the im­portance of a thorough study of all considerations having a bearing thereon is evident. Although the earth road is considered a cheap type of construction, it is probable that a location, when once determined upon, will not be ma­terially changed, even when the road is eventually im­proved. All the factors, therefore, that are considered in the location of a permanent highway should be considered at this time. It is probable that more freedom may be had in the loca­tion of an earth road than in that of the more permanent types of highways, because, in the first place, the road is to be located through virgin territory, where no road at present exists. In the case of the more permanent types, it is probable that an earth road will have already been con­structed near the desired location, and it may be difficult to make a change in the location when improving the road, as farm houses will have been located with reference to this road and fences and property lines established with refer­ence thereto. There are certain fixed points, such as cities, permanent bridges, etc., which are determining factors in the location of the highway, but the engineer should be given considerable latitude in the location between these points. The same principles apply as in railroad location to a considerable extent, in that the road must be laid out so that it will serve the maximum traffic and be the shortest distance between the termini consistent with the proper grades and drainage. Itis not always desirable to locate the road along the line of existing maximum travel, as this traffic may not be following the logical route. The direction of traffic often shifts materially after the improvement of a highway. Drainage is the most important consideration arising in the study of the problem of locating or relocating high­ways. The effect of water on the road may be either the softening of the surface by the water standing immediately upon the surface of the roadway; the washing and cutting of side-ditches, due to excessive flow or steep grades; the softening of the foundation from seepage, where water is permitted to stand along side the road ; or the overflow and washing of the surface of the road itself. To remedy these conditions, it is necessary to provide for surface drainage, cross-drainage, and underdrainage. The surface drainage is taken care of as far as the immediate road surface is concerned by giving the roadway the proper crown. This crown should be sufficient to remove the water quickly from the road surface, and should be as flat as possible consistent. with good drainage. Steep crowns are objectionable, as they cause traffic to track or localize along one narrow area down the center of the roadway. With a flatter crown, traffic is encouraged to distribute itself over the roadway, thus preventing the formation of ruts and the excessive wear which results in wheel tracks down tb~ center of the road. The amount of crown for any road, therefore, de­pends on the degree of permeability of the road surface, and is expressed in inches fall per foot of half-width. For earth road, the crown is usually about one inch per foot of half-width. A 24-foot roadway, then, would be twelve inches higher in the center than at the shoulders. After the water has been removed from the road surface, it must be carried away by means of side-ditches. These ditches should be wide and shallow, and, preferably, have sufficient grade to be self-cleaning. The ditch as cut by the road grader has a very desirable shape, in that the maximum depth, which is the point of maximum velocity and also of greatest cutting from the water, will be on the side farthest from the roadway, while the side adjacent to the road is shallow and therefore will not cut appreciably during fioods. If the longitudinal grade of the ditch is greater than from three to five per cent, depending upon the class of soil, it will cut and erode rapidly; and it will be necessary to take steps to prevent such action, since, if permitted to continue unchecked, the roadway itself will eventually be entirely cut out and only a drainage ditch will remain. A number of low cross-walls made by driving 2x8 lumber at right angles to the ditch will provide a series of steps or drops, which will localize the washing and allow the grade to flatten out between. The tops of these walls should be low enough to provide ample area of waterway above, so as to prevent damming and flooding the road, and should extend far enough into the ground to prevent being undermined by the action of the water pouring over them. In some locations the grade of the center line of the road may be absolutely level and the drainage taken care of entirely by giving the side-ditches proper slope. It is de­sirable to give these ditches at least a one per cent grade, as they will be very troublesome due to the growth of vege­tation, and will require constant cleaning, if constructed on a flatter grade. Another feature which is frequently overlooked is to pre­vent water from being carried a considerable distance on the uphill side of a road. This water should be carried through the roadway at frequent intervals by means of proper cross-drainage structures, so that the road shall not be overflowed by too great an accumulation. A large amount·of water on the downhill side of the road is not so troublesome, as the crown of the road is higher than the adjacent property in most cases, and any overflow from the ditches would spread out over the property rather than the roadway itself. It has been the practice in the past, and continues to be in the present, to drain all farming land as much as possible on to the highways. The roads are made to act as drainage ditches for adjacent property. This is exactly the reverse of what the conditions should be. Since the road surface is much more expensive than an equal area of farm land, it is desirable to drain the water away from the roadway at frequent intervals, and never should it be allowed to be carried along the road and accumulate in sufficient amounts to cause damage from washing. Water should be carried by the shortest route possible to the creeks and principal drainage-ways. Where water stands on the surface of the road due to a layer of impervious material beneath, no amount of work­ing of the surface will appreciably benefit the situation. No amount of working on the surface of a tub filled with mud will cause it to become dry and firm, though a hole in the bottom of the tub will quickly bring about thorough draining and a satisfactory condition of the material. The same thing applies to a roadway. An underdrain must be provided where seepage occurs, to intercept or carry off the water as it accumulates, in order to hope to maintain suc­cessfully any type of road surface. These seeps must fre­quently occur on hillsides, where water is brought to the surface by an outcropping of clay, rock, or other impervious material. It is customary to place the underdrains below the side-ditches, but these on steep grades are likely to wash ~:mt, as the material of the newly filled ditch will cut more easily than the adjacent soil. These underdrains should also be carried away from the road as quickly as possible. As a general rule, it is well to avoid cuts, as they are hard to maintain. It is better to raise the grade slightly and build the entire roadway on a slight fill, or to go around some of the hills, rather than to cut through, as the material gradually washes down the steep slopes of the cut, and con­tinuous maintenance is required to keep the side-ditches clean and in working order. Where a cut is necessary, a ditch should be placed on the uphill side above the cut to intercept surface drainage and prevent unnecessary damage to the side slopes of the cut itself. Wherever possible, it is advisable to follow a ridge rather than to go across it, as a minimum of drainage ditching and drainage structures will be required in this case. It is ad­visable under some conditions to swing a little out of the general direction desired in order thus to decrease the diffi­culties due to improper drainage. Obviously, mashes and sand should be avoided as much as possible. It is undesirable also to lay out a road parallel and adjacent to a stream, unless this location is absolutely necessary, for it is impossible to maintain such a roadway properly, as the foundation will be soft from seepage and the road in danger of damage from floods. It is advisable to cross all river bottoms as nearly at right angles as pos­sible, so that the minimum mileage of roadway will be lo­cated in low lying lands subject to overflow. The question of grades comes up next for consideration. The steepest grade on a road will limit the size of the load that can be hauled over that road, since the load that a team can pull on various grades decreases rapidly as the percent­age of grade increases. It is desirable to keep the maxi­mum grade within reasonable limits. Usually the maxi­mum permissible grade is taken at from 3 to 5 per cent. A two-horse team can pull about 4,000 pounds on the level on a good earth road. On a B per cent grade, the same team can pull only 2,200 pounds ; while on a 5 per cent grade, it can pull only 1,600 pounds. From these figures, it is seen that a team's pulling power is cut in half by a 3 per cent grade, and approximately to one-third by a 5 per cent grade. This shows the necessity of cutting down the steeper grades to a reasonable maximum limit. It is sometimes advisable to go around a hill rather than to go over it, as the distance around may not be any farther than that over the hill. While the latter is usually termed a straight line, it is straight only with regard to horizontal dimensions, and may be very crooked with regard to ver­tical dimensions. Since this matter of grades is usually determined once and for all, and is not changed materially with a change of road surface, it may be considered one of the permanent f ea tures of the construction, and a proper proportion of highway funds spent thereon. While tangents are usually desired in determining tht> alignment of a highway, curves are not always objection­able, unless very sharp and of too short radius for the type of traffic to be handled, or with an obstructed view. It is desirable wherever possible to arrange so that a 500-foot clear view is available. A discussion 8f the construction of an earth road resolves itself principally into a discussion of road-building equip­ment. Before the construction is started, however, it is nec­essary that certain surveys be made. Such surveys have been thought superfluous in the case of earth roads in the past, and the lack of them accounts for the usual poor loca­tion of this type of highway. It is essential that the drain­age areas should be run out in order that the proper size drainage structures may be put in. Furthermore, a profile should be made of the proposed road in order that longi­tudinal drainage may be properly taken care of. These two classes of surveys should at least be undertaken before any kind of road is located. Much of the earth road construction work can be done by means of a road-grader with the assistance of a grading­plow. This machine will shape up the road surface in a satisfactory manner, unless a considerable amount of cut and fill is required, ·. in which case the earth can be most economically moved by slip or drag scrapers and fresnos for short hauls up to about 100 feet. It is perhaps ad­visable to use wheeler-scrapers for hauls of from 100 to. 600 feet, and wagons of some of the numerous types of dump beds for distances above 600 feet. A discussion of this equipment will not be gone into, as it is something with which you are all familiar. The maintenance of the highway after it has been con­structed is one of the most important problems, and one which has been most sadly neglected in the past. If an earth road is properly maintained, this work is very simple in character and does not require a great amount of skill in its performance. The machine most often used in main­taining earth roads iB the road-drag, which may be con­structed of wood or of the more modern type made up of some twns: Whenever earth grading quantities are to be calculated, cross-sections shall be taken, and plotted, at intervals of 100 feet or less. In case it is found that the work may be done with a road machine, cross-sections need be taken only every thousand feet. The sections shall be plotted from the bottom of the sheet upward and so as not to interfere unduly with one another. The ground and grade elevation shall be shown at each section, together with proper station number. Show the area of each section and the yardage between sections. Structural P"lans: Structural plans shall be submitted for all structures included in the project. When standard designs issued by this department are used, blue prints of such designs may be obtained upon request. Binding of Plans: All sheets should be arranged in their numerical order and securely bound on the left hand mar­gin. In binding the sheets, care should be taken that all sheets are properly arranged and evenly matched before binding. In General: In brief, a set of road plans should contain all information necessary to enable the engineer who checks your plans also to check up the items listed on your esti­mate sheet. Please avoid errors in arithmetic. From the foregoing, it will be seen that, in order to proP­erly prepare a set of road plans, much field work must be done. In many respects, highway construction differs widely from railway construction, but the actual field work on the surveys is very similar to that required for railway location. The termini and often several intermediate points are determined before any field work has been done, and often before the engineer has been employed, so his work of lo­cating will involve merely the con:necting up of these points with the most feasible route upon which the road can be economically constructed and maintained. Before any field work is started, it will be necessary for the engineer to make a careful and studied reconnaissance. Sometimes this reconnaissance will consist merely of choos­ing between one or more definite existing roads. After the general location of the line has been determined upon, it is then necessary to make a careful location survey, which should be made as follows: Make the center line survey, measuring all angles and running in all curves. A stake should be set at each J.00 foot station, and closer on curves. On new location and where the stakes will not be disturbed, set them on the center line. Where the located center line is within the Roads and Pavements limits of the traveled way, set stakes on an offset line and record their distance from the center line. To this location line, tie on all topography for a distance of 500 feet on each side. Run center line levels, establishing, bench marks not far­ther apart than 2,000 feet. From the information now in hand, the location plan and center line profile can be made and a tentative grade line established. From this drawing, it can be determined what portions of the work can be done with a blade grader, and what portions must be figured as yardage. On those portions upon which yardage is to be figured, take cross-sections at each 100-foot station, and take any intermediate sections that may be necessary to calculate accurately the amount of earth work to be done. These sections must be plotted as previously described, and the earth work computed from them. For each drainage structure, the boundaries of the drain­age basin must be actually surveyed and its area carefully ascertained, from which information the size of the drain­age structure will be determined. After the surveys have been made, the alignment has been plotted, the grade line tentatively laid, quantities have been figured and the sizes and types of drainage structures tentatively determined upon, call upon the highway engi­neer to have an inspection of the plans made by one of his division engineers. This inspection is made by the division engineer in company with the county engineer, and the ground is carefully gone over, plans in hand and the in­formation on the plans being compared with conditions on the ground. The grade line should never be inked in until after this inspection has been made and the grade line approved by a representative of the Highway Engineering Department. Also, where you are in doubt about any part of your loca­tion or other features of your plans, do not ink in until these features are definitely determined upon by consultation with the Highway Department's engineer. DRAINAGE AREAS AND CULVERTS BY G. G. WICKLINE Bridge Engineer, State Highway Department Drainage Areas: In determining the type of drainage structure for a particular location there are a number of things to be taken into consideration, as the amount and frequency of rain storms, stream characteristics, watershed area and the slopes, whether they are prairie, timber, or cultivated, or whether they are steep or flat, and the grade line of the stream bed and other elements affecting the safety of the culvert or bridge. An observation of existing structures on the same stream or in the same locality, will furnish some information that will be of assistance in de­termining' the proper size and type of structure to be used. Formulas: Where data on existing structures are not available on the same stream, there are a number of form­ulas which may be used that will give the approximate area necessary, provided care is taken in using the proper terms in the formula to fit the local conditions; but, wherever possible, the area so calculated by a formula should be com­pared to the area of an existing structure for a similar lo­cation, if there be any. Particular attention should be paid to ascertaining the high-water marks by the observa­tion of drift or by interviewing the residents in the vicinity. In the selection of the proper waterway area, the engineer should make careful field observations and use his best judgment. There are a number of waterway area formulas and tables, no two of which will give the same results for all conditions. Most of them are prepared for special con­ditions in some particular locality, and do not fit other lo­calities, unless conditions are the same. The use of tables and formulas should not be made unless, as stated above, all conditions affecting them are known. Duns Drainage Table: This table was devised by James Dun of the A. T. & S. F. Railroad, and is widely used by the railroads in the Middle West. Dun's drainage table is intended to be used for all sized structures. The slopes are not taken into consideration as much as the Talbot formula. Talbot's Formula: This formula was devised by Pro­fessor A. N. Talbot, and is used extensively for the deter­mination of waterway area for highway culverts by the Federal Bureau of Public Roads and various state highway departments. Since the greater portion of the work of the State Highway Department is in conjunction with the Fed­eral Bureau of Public Roads, Talbot's formula is used al­most exclusively for the determination of waterway drain­age structures and is stated as­ 4/ 3 .4=Cv' M Where A represents the area of the opening of culvert in square feet; M, the watershed area in acres; and C, a co­efficient depending upon the slope, soil, and vegetation of the watershed area. Professor Talbot recommends the following values for C: 1.0 for abrupt slopes; 1/3 for rolling agricultural country; and 1/ 5 for fairly level country. Provision should be made 1n the selection of the water area of culverts for all ordinary floods, with a good margin of safety. The Talbot formula as given above is supposed to provide for this margin of safety, but, as indicated above, it is well to compare the results with those of other structures upstream or down­stream from the proposed structure. There are a great number of waterway area formulas that are used for de­termining the storm water run-off for sewer designs, and should not be used in connection with the design of culverts, unless a very long culvert is to be used in which the water on the upstream side can be impounded by the roadway embankment, so that no danger of overflowing the road will result. Grade Line of Stream Bed: The grade line of the stream bed should be taken into consideration for the upstream and downstream sides of the culvert. Should the downstream side have a flat grade, there is danger of the stream channel becoming filled with silt, and the flow line of the culvert being raised, thereby decreasing the waterway area of the culvert. In most cases, it is possible to clean out the chan­nel so that the flow line may be maintained at a constant elevation. Character of Watershed Area: If the watershed area is cultivated land, prairie, wooded, or covered with vegetation, judgment should be used in the selection of the proper size of water area for culverts, for cultivated land is likely to carry considerable amount of silt. In watershed areas upon which there is a heavy growth of weeds and vegetation there is likelihood of trash accumulating at the upstream end of the culvert, restricting the flow of water through the culvert. The channel of the stream should be cleared and opened on each side of the culvert a sufficient distance to admit an amount of the storm water to develop the full capacity of the culvert. A contracted rough, irregular, channel has considerable effect on the carrying capacity of the culvert. Selection of Proper Type of Culvert: For the small cul­vert requiring only a few square feet of water area, the circular type is usually selected. A box type of concrete culvert of a minimum size of 2x2 concrete culvert can be built with a special type of collapsible form. A smaller type than this is usually of the· precase circular type, if concrete is used. All small culverts should have a good margin of safety in size of waterway area, for the cost for the different sizes will not vary greatly. On most high­ways through the flat prairie country, clear height of cul­vert can not be obtained without making the grade of road­way higher than necessary. Low wide waterway areas are preferable to high narrow ones. From the principle of hydraulics, a criterion is established that for a rectangular opening of equal perimeter a maximum discharge is given when the width is twice the height. The ordinary box cul­vert as shown in the plans of the State Highway Depart­ment conform approximately to this rule. Pipe Culverts: Pipe culverts may be constructed of con­crete, brick, stone, vitrified clay tile blocks, segmental clay tile blocks, corrugated galvanized iron, each material having more or less merit, dependfog upon the locality in which it is to be used. All of the foregoing types of culverts should be ccnstruc:te·1. " ' t'-ie best r :f tte 1 esne~:ti.ve materials. in a careful" workmanlike manner. For further information, see the specifications (Item 23), and the plans for pipe cul­verts of the State Highway Department. Head Walls: All pipe culverts should be provided with substantial head walls of a type equally permanent and sub­stantial as the culvert itself. See plan of the State High­way Department. Vitrified Tile, Corrugated Iron, Cast Iron, Pipe: These types of circular culverts require special care in arrange­ment of bed for placing, in order to secure an even bearing. The back-fill around the lower portion of the culvert should be thoroughly tamped. It is also important that a proper depth of fill be provided over the culvert. Stone Culverts: Stone culverts can be used to advantage in certain lo'calities where ledge stone of good quality is plentiful, and if properly built give good results. Concrete mortar should be used wherever possible, although many railroad companies have built stone culverts without the use of mortar. Stone culverts may have the top slab of ledge stone, if of the proper thickness. The bridge engi­neer of the Federal Bureau of Public Roads recommends the following thickness for small culverts: Span Thickness Width Length in Feet in Inches in Inches in Inches 2 10 20 4 3 12 24 5 4 15 30 6 In most localities, it would be difficult to secure ledge stone that would conform to the requirements of the fore­going table, so it would probably be better to provide for a reinforced concrete top slab. See Plan G 250, on file in the State Highway Department. Concrete Cufrerts: The monolithic type of reinforced concrete culvert is strong and durable, and a very popular type of construction at the pr~sent time. The following plans are used by the State Highway Department: C 1, reinforced top and bottom slabs with plain side walls and plain head walls parallel to the center line of roadway. C 2, reinforced top and bottom slab with reinforced wing walls at right angles to the center line of roadway. For low small clear heights, this type of culvert is the most economical, but it has the objection that when carrying its full capacity the water has a tendency to slop over the sides of the downstream wing w~lls and wash away the embank­ment slope, particularly where new embankment is con­structed. If a small amount of rip-rap is used, or the em­bankment sodded with bermuda grass, this objection can be eliminated. C 3, with reinforced top and bottom slabs and reinforced wing walls at an angle of sixty degrees with the center line of roadway gives a very good type of culvert and is most commonly used on state and federal aid projects. The flar­ing wing walls allow the water to spread out after leaving the culvert, without damage to the embankment slopes on the downstream side. C 4, reinforced concrete top slab plain side walls resting on a spread footing with a reinforced wing walls at an angle of sixty degrees with the center line of roadway. This type of culvert is adapted to localities which have good foundation of shale or clay, and the danger of undermin­ing is not very great. Segemental Clay Tile Bwck Culverts: Plan SB 1 of the State Highway Department provides for the use of seg­mental clay tile blocks. A test was recently made on this type of culvert which demonstrates that, if properly con­structed with the proper amount of fill over top, this type of culvert would have ample strength, and doubtless this type of culvert can be used to advantage in many parts of the state. Corrugated Galvanized Iron Culverts: This type is widely used and easily placed, and great claims for per­manency and strength are made by its manufacturer.s. No doubt if pure ingot iron, properly galvanized, and rivets equally permanent are used, this type can be emplbyed to good advantage for various types of highway construction. Some slight allowance should be made in calculating water­way area for the corrugations. Plain Concrete Arch Culverts: This type of culvert can be used in some localities where rock foundations can be secured and where the concrete aggregates necessary can be laid down at the culvert side at a low price. See Plan G 248-249 of the Federal Bureau of Public Roads, on file in the State Highway Department. Timber Culverts: These culverts should not be used on permanent road construction, but may be used temporarily in localities where timber of the proper kind is available locally and where the culverts to be built are a considerable distance from the railroad. There are some localities in East Texas where the land is poor and available money for highway construction is very limited that use timber cul­verts to fair advantage. Paved Concrete Fords or Dips: This is a type of over­flow crossing, and is used in the place of culverts in certain localities where the rainfall run-off is rapid. This type is more particularly adapted to West Texas, where rain storms are infrequent. They may be concrete, flat stone, asphalt, macadem, or a good compacted quality of gravel. Good judgment should be exercised in the use of concrete dips, as they should not be used if there is any liability of the stream's filling up on the downstream side and leaving the dip covered with mud. Maintenance of Stream Channel: All culverts should be inspected at regular intervals after floods. The stream channel should be kept clear from drift and trash. Depos­its of silt should be removed both upstream and down­stream, more particularly on the downstream side. There are some localities in Texas where a number of culverts are completely choked up with silt and trash and where water has washed out the road. This illustrates the necessity of providing plenty of head room and a slight margin of safety in the size of the w:::i.ter­way area selected. PREPARATION OF SPECIFICATIONS AND CON­ TRACTS BY R. G. TYLER, Adjunct Professor of Highway and Sanitary Engineering Specification-writing is as difficult as it is important. All too frequently, rather than go to the trouble of making a thorough study of the problem in hand so as to be able to specify intelligently just what is desired, the engineer patches up so-called Standard Specifications to meet local conditions, lets his contract, and finds later that they may or may not fit. A thorough knowledge of materials and methods is neces­sary for the proper construction of specifications. It is absolutely essential that the engineer should have a clear and definite conception of just what he wants, and be thor­oughly familiar with all of the details entering into the problem in hand, in order to set down these details in a clear and concise manner. The ideal to be striven after in preparing the specifications is to state exactly what is de­sired, and in euch accu,rate, specific, and adequate language that it will be impossible to mistake his meaning and give it a wrong interpretation. The practice which formerly prevailed, of inserting ambiguous blanket-clauses in a:a at­tempt to cover a point upon which the engineer was not en­tirely clear in his own mind, is to be condemned as being unfair to the contractor and likely to bring about misunder­standing between the contractor and the engineer. As highway construction is not an exact science like mathematics, it is to be expected that there will be differ­ences of opinion among the authorities and leading engi­neers in this branch of work. With regard to many of the details as to materials and methods of construction, and in preparing specifications, it is well to study the various opin­ions of experts in passing judgment on the problems being considered. It is customary to include several documents in what may be termed the general contract, each of these documents being important and necessary thereto. These documents are usually as follows : 1. The advertisment for proposals. 2. Instructions to bidders. 3. The proposal submitted by the contractor. 4. The specifications. 5. The contract proper. The law requires that municipalities and other units of government shall advertise for bids on all work or pur­chases costing $500 or more. These advertisements should appear in the leading papers published in the locality where the work is to be done, and should be published a given length of time before the opening of bids. The engineer who desires to secure the best results for his employer will advertise his contemplated work where it will receive the attention of the largest number of. contractors in the par­ticular line of work in which he is engaged, in order that he may secure as many bids as possible, thereby insuring a fair price for the municipality or county by which he is engaged. It is desirable to let the work in large enough contracts to invite contractors having strong and well organized con­cerns to submit bids, and to keep the cost of shipping-in the necessary plant from running up the unit cost to any con­siderable amount. There are other considerations, also, which should be taken into account in deciding upon the size of the contract, such as the amount of work which can be done in one working season and the desirability of mak­ing the contracts small enough to permit the more numer­ous smaller contracting firms to enter the competition. These questions must be given thorough consideration by the engineer, and local conditions will assist in deciding what should be done. The tendency now is, however, to let road work in larger contracts, thereby inviting the stronger and better equipped firms, who are able to carry out a larger amount of work in a given season, to submit bids. Obviously, the contractor who can work on a large scale can give a closer price, since he is not forced to figure on prices of material and labor conditions so far in the fu­ture as the smaller contractor, and it is to the advantage of the municipality or county to have its work done quickly in order to be as small an inconvenience as possible to the local population. As to the advertisement itself, there are two general classes in use. One is brief, and states merely that bids will be received for a given type of work at a fixed time and place, and the amount of the certified check which must accompany the bid. This class of advertisement specifies that complete plans, specifications, and contract covering the work in question may be seen in the offices of the en­gineer, and it has the advantage that the contractor is re­ferred directly to the source of authentic information, so that he can get all the information desired and that there shall be no misunderstanding arising from a possible con­flict in statement between the advertisement and the speci­fications. The second type of advertisement is longer, and gives a condensed statement of the kind of work to be done, the schedule of quantity of work involved, and various other particulars pertaining to the contract to be let. This class has the advantage of giving the prospective bidder enough information so that he can determine without going over the plans and specifications whether the work will be of the kind or amount which he is equipped to handle. This longer form of advertisement is sometimes reuired by law, but, if not, the shorter form usually' seems preferable, as it refers the inquirer directly to the official source of infor­mation as above mentioned, thereby avoiding all possible confusion. From a standpoint of cost, also, this is desirable and is often a matter of some importance. INSTRUCTION TO BIDDERS The instructions to bidders should include only such in­formation as may be necessary to assist the bidder in properly and intelligently preparing and submitting his proposal. It is proper in the instructions to refer to the specifications and contract for all general and detailed in­formation concerning the work to be done but it should not be permitted to overlap in any way the field of the specifications and contract. It should be made as brief as possible, and its usefulness should be at an end when the contract has been signed. PROPOSAL The proposal should contain definite statements as to what the bidder proposes to do. He should submit both unit prices and totals for each item specified, and it is customary to put these amounts both in writing and in figures in order to avoid error. The total costs are figured on the approximate quantities given in the engineer's esti­mate, and these quantities are subject to change under the conditions set forth in the specifications. The proposal, also, contains the address of the bidder, and is accompanied by a certified check payable to the order of the contractee ; the check to be returned to the bidder if he i& unsuccessful or upon the execution of the contract and the filing of the bond called for by the contract. SPECIFICATIONS There are three general classes of engineering specifi­ cations. In the first class, the engineer specifies in detail the class of materials which he desires to be used, and the methods which, in his judgment, will bring about the desired result. In the second class, the engineer specifies as to the results to be obtained, leaving the materials and methods, at least partially, to the judgment of the con­ tractor. In the third class, the engineer specifies both as to the materials and methods and as to the results to be obtained. Either of the first two classes of specifications is permis­ sible, and the one may be chosen which the engineer believes will produce the best results. The third class, however, though frequently met with, should never be tolerated, as it is obviously unfair to the contractor to specify what ma­terials he shall use and exactly the methods to be followed, and then demand that certain results be obtained. Ob­viously, it is entirely possible that the result desired may not be secured by the use of the specified materials and methods, and either one or the other should be covered in the specifications, but not both. In highway work where the type of road to be built is of a standard form, and where the materials and methods have been standardized by years of experience and paving practice, it is preferable to use the first type of specifica­tions. Here the engineer is supposed to have sufficient ex­perience to be able to state what he desires in the way of materials and how he wishes the work to be done. The result that will be obtained depends largely upon the ex­perience of the engineer, and so long as he properly su­pervises the work and supplies the necessary inspections to see that his specifications are carried out, he should as­sume the responsibility as to the results to be secured. It is unfair, also, to expect a contractor to guarantee work done under this type of specifications, and he should not be expected to do so. Where, however, the type of construction is patented, or some of the methods to be employed or the materials to be used are new, it is advisable to use the second type of spec­ ifications, and state only as to the results to be obtained rather than as to materials and methods to be employed. In this class, it is perfectly proper and legitimate to require the contractor to furnish bond guaranteeing the work to come up to certain standards and to insist upon the making good of any defects which may appear after the completion of the contract and during the life of the guarantee. In this case, the work is being done with materials or methods based upon the judgment of the contractor, and he should assume the responsibility as to the results obtained. In writing up specifications covering patented pavements or processes, it is not usually advisable to copy in the speci­ Roads and Pa'vements fications furnished by the patentor, as he will naturally make his specifications as brief as possible, and not bind himself down any more than he thinks absolutely necessary to secure the contract. While firms that have been doing business on a large scale undoubtedly present specifications which are fair, and which can be relied upon, there are times when such specifications may be carefully drawn up so as to evade final responsibility. It is desirable, there­fore, that the engineer should use his own judgment and make any changes that he may deem necessary in these specifications, leaving it up to the company concerned as to whether they desire to submit a bid on his revised specifi­cations covering their patented process or products. Very often specifications are encountered whiih are one­~ided and manifestly unfair. In the drafting of specifica­tions, this, naturally, should be avoided; but there is a tend­ency to bind the contractor in every way possible, and to make the requirements so binding and drastic as to prevent many bidders from submitting figures on the work. And the prices received will be higher than they would have been had the contractor had a reasonable assurance of re­ceiving a square deal. The rights and authority of each party to the contract should be accurately set forth, so that there shall be no possibility of a misunderstanding. It has been customary in many cases to specify that the engineer shall be the final authority on all questions arising between the city or the county and the contractor. This, however, is often unwise, and perhaps illegal. The reason for such a clause in speci­fications is the supposition that the engineer is a disinter­ested party in the transaction, and one who is competent to pass judgment on the questions which arise. The engi­neer, however, is not always disinterested, as it is his desire, and properly so, to secure the best results for his client for the funds available. He is paid by his employer to look out for his interests, and may be inclined to loot at all questions from this point of view. It is true that his sense of justice and professional honor will in the majority of cases cause him to pass a fair judgment upon the ques­tions involved, but no engineer desires to be placed in so difficult a position, and it is both unfair and unvdsc to re­quire him to assume it. There are, however, some matters where the deciciion of the engineer should be final, unless improper motives can be shown. He should be the final judge as to "\Yl1ether the quality of the materials and grade of workrnar.ship are in accordance with specifications, and as to the quantity of work which has been actually performed. Methods of measuring the work completed and paying therefor should be stated in a definite manner, as careless­ness in this feature may be the source of misunderstanding and disputes. The method of determining prices to be p'1.id for extra work should, also, be set forth, as it is impossible to forsee all contingencies which may arise and require prices on every feature which may be encountered. A quite satisfactory method of meeting this situation is to specify that the contractor shall be paid cost plus a given percent­age which would allow a fair profit for all work for which unit prices had not been submitted. It is desirable, how­ever, to require that prices be submitted on each class of work which it is contemplated shall be done, and upon all features which may arise during the performance of the work. This seems better than submitting a price of so much per square yard of completed road surface, as the contractor is able to submit a price on each individual item which may arise, and is not required to make additions for such items as can not be readily foreseen, and the prices so submitted are likely to be fairer to both parties than in the latter case. The relationship existing between the engineer and con­tractor should be one of cooperation, and it should be the engineer's desire to assist the contractor in every way pos­sible in securing the results desired at the lowest possible cost consistent with good workmanship and materials. No en