amount of relief. On comparatively level land the individual elevations should be preserved on the map. These elevations are especially valuable in depressions and along ridges. 14. Classification of irrigable lands.-Topographic maps of irrigable lands should show, in addition to the topography, a classification of the lands. Notes should be made of the character of the soil, vegetation, etc., including information as to the areas covered by timber, wood, and brush. Depth of soil should be noted if less than 4 feet, as shallow soil often makes proper leveling of the surface impracticable. With reference to irrigability, the land will be divided into two general classes, irrigable and nonirrigable. This can be best done on a piece of tracing cloth placed over the map and showing the public land subdivisions by 40-acre tracts or lots. Irrigable land will be classified as first, second, and third class. First and second class lands are both irrigable and agricultural, and third class land is irrigable, but not agricultural, owing to infertility or presence of excessive quantities of alkali or water. By nonirrigable land is meant land that is too high or too rocky or broken to permit of successful irrigation. On the tracing cloth the classification should be indicated in colors. The land under cultivation should be shown in its appropriate color with fine black lines drawn across it. In addition to the color sheet there should be detail notes kept, describing the soil, topography, and vegetation of the various subdivisions on the tracing, the subdivisions being referred to by numbers. All wells should be located and the distance to water from the surface of the ground noted. LEVELING. 15. Primary levels.-The following rules for primary leveling should be closely adhered to: (a) No sight more than 300 feet in length should be taken, except under unavoidable circumstances. (b) Record distance in feet for both fore and back sights and keep them as nearly equal as possible. (c) Avoid lines of sight that are less than 2 feet from the ground surface at any point, particularly when the air is "boiling." (d) Levelmen and rodmen should keep their notes strictly independently and in such a manner that they will not turn the leaves of their note books at the same time. (e) Give complete information regarding source from which initial elevation was taken. (f) Establish bench marks for each mile run. Standard bench marks (posts and tablets) should not average more than 3 miles apart. (g) Be careful to use firm turning points. (h) All primary level circuits must close with an error not exceeding 0.05 D, where D is the length of circuit in miles. 16. Secondary levels. On secondary or flying level lines, lengths of sights are not limited, turning pins are not required and every effort should be made to save time. Benches should be left at fre quent intervals and should be well described, but standard benchmark posts must not be established on such lines. Elevations of topographic control points along the line, such as road corners, summits, and depressions, bridges and water levels, should be determined and marked in some way so that they will be readily found and read by the topographer. No limit of error is prescribed for this work, the general understanding being that a closure within a fifth of the contour interval used is sufficient. 17. Triangulation.-Where it is necessary to measure the angles of a system of triangulation for the control of the topography of a large reservoir site or of a large area of irrigable land, and where the instrument used reads to 20 or 30 seconds, the following method is generally of sufficient accuracy, the signals being in the order A BC-A: First set: Telescope direct-read on A B C — A. Shift the limb 90°. Second set: Telescope reversed-read on A B C — A. If more than two sets are necessary the limb should be shifted, between sets, 180° divided by the number of sets. In all cases read both verniers. Observations on Polaris for azimuth should be made at the beginning and end of the triangulation and the entire system should be properly adjusted. Each triangulation point should be permanently preserved by means of a stone or concrete monument. INVESTIGATION OF MATERIAL AND FOUNDATIONS. 18. Investigation of material.-On all surveys of dam sites and of canal lines on which estimates are to be made care should be taken to ascertain the character of the material to be moved and to indicate upon the map the class under which it falls. So far as practicable the standard classification for excavation adopted by the service should be used. 19. Borings and test pits.-Borings and test pits should be made to determine the depth to bed rock or the character of foundation at proposed dam sites, and the character of material along proposed canal lines. Careful records should be kept of the material encountered in sinking pits and borings and samples should be collected and diamond drill cores saved. Each sample should be carefully marked with the depth from which it has been obtained, as well as with the location of the hole. WITHDRAWAL AND CLASSIFICATION OF LANDS. 20. Reports on examination of projects.-On completion of the examination of a proposed irrigation project, complete recommendations relating to action to be taken in connection therewith should be made to the director. If reservoir sites or the irrigation of lands have been considered feasible, all lands included therein should be recommended for preliminary withdrawal, the description thereof being given by entire townships if necessary. Lands for reservoir sites should be listed separately from irrigable lands. One of the most essential parts of the work of preliminary investigation for an irrigation project to be constructed under the reclamation act is to record and report the amounts of water diverted by the various ditches and reservoirs taking water from the proposed source of supply; also the maximum capacity of each of such ditches or reservoirs in use. Any information relating to legal decisions concerning water rights and the best sources of information concerning them will be of great value in subsequent investigations. 21. Reports on lands required for reservoirs.-As soon as the maximum elevations of the water surfaces of proposed reservoirs have been determined, the flow line should be located and connected where possible with the public land surveys, and the engineer should thereupon forward to the Washington office a list of the lands required by the reservoir and appurtenant structures, including such unflooded marginal strip as may be necessary, not less than 100 feet wide. A wider strip may be provided if necessary for the proper maintenance and protection of the reservoir and headworks. 22. Reports on nonirrigable lands.-When the irrigable lands have been determined by the survey, the engineer shall forward to the Washington office a list of the nonirrigable lands included in the preliminary withdrawal. 23. Avoidance of publicity. In making a reconnoissance or preliminary survey publicity should be avoided concerning the details of the project and especially the land that may be temporarily withdrawn pending survey. It usually takes two or three weeks for the order of withdrawal to reach the local land office after the request has been made by the director. If the information becomes public before the order of withdrawal is made the lands will be subject to speculative entry and difficulties may result. 24. Description of lands.-In describing lands for withdrawal for reservoir sites and for restoration to entry the subdivisions used may be smaller than the smallest legal subdivision (40-acre tracts, or lots). They should, however, be consolidated as much as possible, using whole sections, quarter sections, or half quarter sections where possible. In describing lands the following general rule should be observed: The townships should be given in order of ranges; for instance, T. 1 N., R. 1 E., R. 2 E., R. 3 E., etc. The quarter sections should be placed in the following order: NE., NW., SE., and SW. Always insert "and" before the last subdivision of each section. Lot numbers should be given first and half sections last. Always state the principal meridian of the survey and the State in which the land lies. The following is a specimen for arrangement, order of description, and punctuation: Where the public-land surveys have not been extended over the lands in question, but are not far distant, it will be advisable to project the public-land surveys, making liberal allowance for possible variance in the final land-office surveys. When the public-land surveys are at a considerable distance the descriptions should be made with a view to their being plotted on the State maps issued by the General Land Office. The fact that any tract is included in one of the so-called "school sections" should not prevent a recommendation for its withdrawal, because the status of such lands depends upon a variety of conditions, and the decision in the matter must be left to the General Land Office. 25. Examination of land titles.-The examination of title to the lands involved in the various irrigation projects must be made at some time during the investigation. It is necessary before construction can begin to know as to each tract whether it is public or private land; while in connection with the purchase of right of way for canals or of lands to be flooded in reservoirs, a complete abstract of title will be required. The first step will be to obtain a copy of the record of the local land office to show the present status of each tract. It will not, of course, be necessary to copy notes of entries that have been canceled, or contests that have been decided, or the like. This record will give the nature and number of the entry, a description of the land, the name and post-office address of the entryman, and other details. Such a record will show what land is vacant, what land is entered, and what land has been patented. A book has been prepared for making these abstracts and can be obtained on application. LAND SUBDIVISION SURVEYS. 26. Authority for making supplemental land surveys. The first section of the act of Congress entitled "An act providing for the subdivision of lands entered under the reclamation act, and for other purposes," approved June 27, 1906 (34 Stat., 519), authorizes the Secretary of the Interior to fix a lesser area than 40 acres as the minimum entry whenever, owing to market conditions and the special fitness of the soil and climate for the growth of fruit and garden produce, a lesser area than 40 acres may be sufficient for the support of a family. The size of such entry or farm unit shall be not less than 10 nor more than 160 acres. Whenever it may be necessary, for the purpose of accurate description, to further subdivide the lands to be irrigated under the provisions of the reclamation act, the director of the Reclamation Service may cause subdivision surveys to be made by the engineers of the service. These subdivisions shall be rectangular in form, except in cases where irregular subdivisions may be necessary in order to provide for practicable and economical irrigation. All subdivision surveys differing from the regular fractional method of subdivision of a section must be approved by the Commissioner of the General Land Office, and field notes and plats thereof must be filed in his office as supplemental surveys. The Secretary has authorized the service to make resurveys and resubdivisions of the areas required for reservoirs or other irrigation works and the areas bordering thereon, and to prepare supplemental plats of these areas, designating them as lots. Before proceeding with a supplemental survey, the project manager will advise the Washington office of the nature and necessity of said survey and furnish all important data relative thereto, together with a rough diagram. Whereupon the Washington office will prepare detailed instructions, outlining the method of procedure, and transmit same to the project office. The chief of construction will designate an engineer, assistant engineer, junior engineer, or competent surveyman to make such subdivision surveys, subject to the approval of the director or chief engineer. But, if surveys are necessary to identify parts of legal subdivisions to be released from reclamation withdrawals, which can not be described in terms of legal subdivisions, such surveys are to be made by the General Land Office, the cost thereof to be payable from the regular appropriation for surveying the public lands. (See also Restorations.) 27. Subdivision into small farm units.-When it is advisable to make field subdivisions into rectangular farm units of less than 40 acres, the officer designated shall make the necessary surveys and establish the corners in strict accordance with the requirements of the current "Manual of Surveying Instructions for the Survey of the Public Lands of the United States and Private Land Claims," issued by the General Land Office, and in the reestablishment of corners and subdivisions of sections shall be governed by the current circular of the General Land Office on "Restoration of Lost and Obliterated Corners and Subdivision of Sections." Full and complete field notes of all lines run and a careful record of the sizes and descriptions of all corners in regular subdivisional surveys or surveys for the restoration of lost or obliterated corners should be filed in the offices of the chief of construction and project manager, |