A major duty of field personnel is the proper, accurate, and timely staking of control points on the project. The importance of staking and handling of related fieldwork cannot be over emphasized because the contractor's progress often depends on adequate staking. Information concerning staking operations preformed by the contractor’s personnel is contained in EPG 238.4.27.2. Information concerning MoDOT’s quality assurance checks of the contractor’s surveying work is contained in EPG 238.4.29. To ensure proper accounting for each of the various surveying tasks involved with construction surveying, the correct coding must always be used.
When contracts are awarded for improvement projects, the contractors must be contacted to determine their work schedule. This will enable staking activities to be completed in advance of their operations. The contractor will furnish the stakes necessary for this work. Arrangements must be made for immediate delivery.
It is essential the contractor's personnel understand the staking methods to be used and the information that is shown on the stakes. Carefully explain this information. If there is any doubt of complete understanding, the contractor is given a written explanation on "Documentation Record", Form C-258. This written record can ensure the contractor’s work is successfully completed.
Before staking begins, a preliminary field check is conducted with the plans to become familiar with project expectations. This check may identify additional requirements that are necessary to serve properties not shown on the plans that may have been in existence at the time right of way for the project was secured. No additions, deletions, or revisions are made to entrances to property that was obtained by condemnation or to controlled access right of way without written approval of the district engineer.
All field notes are recorded directly in the computer using the Survey Module Incorporated (SMI) system (refer to MoDOT survey training materials). Additional information (i.e., lists and descriptions of control points and chains, bench marks, etc.) is placed in standard field notebooks, available by requisition from the district office. Do not use loose-leaf books. Each notebook must be identified on the front cover as to subject, (alignment, cross sections, etc.), project, job number, route, and county. The name and work address of the resident engineer is shown on the first page of the book to ensure it’s return in case of loss. A table of contents is shown on the second page. The date, weather, and names of field personnel are included as part of the SMI entry for each day's work.
On larger projects, separate notebooks are used for each operation (i.e., alignment, cross sections, structures, etc.). On smaller projects, several items such as pre-construction cross sections, bench levels, slope stakes, and final cross sections may be combined in one field notebook. This is not only economical but saves filing space.
Legibly record notes so others may readily interpret the information. When it is necessary to revise or delete any information entered in the field book, the entry is crossed through, initialed, and an explanation for the revision or deletion is made unless the reason is apparent. Good complete notebooks are valuable project records. They must always be kept clean and dry, and stored in a fireproof safe.
When six or more field books (excluding diaries) may be used for a project, a master index of all field data is kept in a separate field book. The master index is prepared by listing all items in the same sequence as in the contract. Several items may be listed on a page depending on the number of entries anticipated for each item. Additional recorded data other than pay items (e.g. alignment notes, bench levels, cross sections, slope stakes, structure stakes and similar items) can be easily located if they are included in the master index.
The master index should be brought up-to-date at least monthly. Otherwise, the recording of information will become unduly time consuming and the effectiveness of the index will be reduced. The master index, completed in detail, will be submitted with the final plans. Each individual field book shall also be indexed.
The plans, including all curve data, are checked and notebooks prepared before staking begins. A set of plans must be available to the staking party at all times. Plan errors, found during staking, are made on field plans as well as in the notebooks. The resident engineer and all effected project personnel must be promptly informed of these errors.
A well-prepared field book permits the survey party to proceed without delay. Alignment can be recorded in the same field book or included in a separate field book. Leave plenty of space in the notebook. Crowding of notes can lead to inadequate information. An accepted method for recording information in the notebook is available.
Obtain the beginning station number of the project from the plans. This station number is inserted on a line near the bottom of the second or third left-hand page of the field book. List stations up the page consecutively from the beginning station on every fourth line (For metric jobs, use every fifth line, listing stations at 25 m intervals, such as 1+000, 1+025, 1+050, etc.). Enter the station and offset of useful control points computed or shown on plans such as P.O.T. (point on tangent), P.C. (point of curvature), and P.T. (point of tangency), including the corresponding coordinate information. Insert them at the proper place in the field book according to station numbers. List control point numbers and chains.
It is advisable to plot right of way and easement lines, showing widths on each side of the centerline, on the right hand page of the alignment book.
The construction staking party has three main functions:
A survey party usually consists of four people; an instrument operator, a data collector operator, and two survey assistants. The party chief generally acts as note keeper and computer operator. The survey assistants must be agile, since they perform much of the legwork necessary in survey. Regardless of the makeup of the survey party, all construction surveying activities within MoDOT right of way must be performed under the supervision of a professional land surveyor (PLS) or a professional engineer (PE).
Members of the survey party must dress for outdoor work in keeping with the season. They must remember that sudden weather changes are common. At times, overshoes or heavy boots may be necessary. A piece of lumberman's chalk (called “keel”), felt tipped marking pens, and spray paint are carried to mark required information on stakes, turning points, etc.
The construction survey party reruns survey lines, establishing location and grade of structures and pavements, and takes cross sections necessary to measure materials moved in construction of the project. Members of the survey party must be familiar with the equipment, the method, and the order of work to accomplish the required tasks since the members of the party are often too far apart to effectively communicate. Hand signals are used in these situations.
The resident engineer organizes the staking party according to field conditions and available personnel rather than maintaining a set number on each party.
It is important to provide all necessary equipment to the survey party when it is organized. Important equipment includes the total station (the EDM and the survey data collector software) the prism pole and the level. The EDM can also be used as a level. Other tools such as tape measures of various types, range poles, level rods, plumb bobs, sledges, axes, brush knives, etc., are required as necessary dependent on the particular project.
Available equipment must be checked to be sure it is in good condition. The EDM is adjusted for current weather conditions using a thermometer and barometer. It is annually cleaned and calibrated by a certified technician. Checks against known controls are made quarterly, or more often if needed, at the project office and documented using the Survey Information Manager (SIM).
Stakes are made from a good grade of lumber. They are planed on both sides to permit clear marking. They are 1" x 4" x 18" in size, cut diagonally. These are satisfactory for right of way stakes, slope stakes, guard stakes, etc. Hubs for permanent points and for staking culverts are 2" x 2" x 18" while hubs for bridge staking are 2" x 2" x 24" to 30", or 2" x 4" x 24". Where hubs are to be driven in rocky soil, shorter hardwood stakes can be used. Paving stakes are 2" x 2" or 2" diameter hardwood of a length to ensure they will not be disturbed during construction operations. In rocky subgrade, railroad spikes, rebar, and 80d nails can be used.
Various hand signals may be used during the survey when the radios are not available. When setting a point on a line, the instrument person signals the survey assistant to move left or right to set the point by a wave of the hand or arm in the required direction. The longer the wave, the more movement is necessary. When only a very small movement is required, the signal is a sharp movement of the hand. A white cloth can be used when visibility is poor.
When leveling, once the instrument operator has taken the rod reading, a wave of the hand tells the survey assistant that they can proceed to the next rod location. When a turn is desired, the instrument operator makes a rotating motion with one arm directly overhead.
Information concerning computation of curve data can be found in a number of engineering handbooks. Computations are generally performed on a computer or the survey data collector.
A spiral transition at each end of circular curve provides a gradual transition from tangent roadway to the full shper elevated curve. The spiral transition has the property of ever-increasing curvature, starting with an infinite radius and ending with the same radius as the horizontal curve. Spiral and super elevation information is found on Standard Drawings 203.20 and 203.21. Generally, only those curves with a radius of 2864.79 ft or less have spiral transitions. Computations are generally performed on a computer or the survey data collector.
Accepted survey methods are used in staking and establishing horizontal control. Control points are set using the Total Station and recorded in the field book. The coordinate information is stored in the survey data collector for future use. If control points are lost, or are not referenced, they must be set from known points that can be located. All control points set must be referenced. All ties for these points are recorded in the field book for future use.
On occasion an alignment will contain a station equation. An equation refers to a point on the survey that has 2 station numbers. For example 185+60.3 (back) = 185+24.7 (ahead). This is a plus equation of 35.6 ft. All equations shown on plans must be observed.
Specifications describe the method of measuring clearing and grubbing units (Section 201 of the Missouri Standard Specification for Highway Construction). When required by specification, the number of units must be determined. The area of each unit is laid out and only those containing clearing are counted. Consider those areas that are marked on the plans to be undisturbed. At this time, it can be determined which clearing units are to be grubbed, based on proposed cut or fill in each unit. A complete record is made in the field notebook of the units counted. The contractor's representative will be present when the count for the record is made. If the contractor's representative is not present, a memorandum from the contractor stating this fact is necessary.
Before running levels or establishing elevations for construction use, a set of levels must be run to check elevations of bench marks shown on plans and to establish additional bench marks. During this check, length of foresights and backsights are kept approximately equal thus minimizing any error introduced by a level out of adjustment. Each benchmark is used as a turning point. It is not advisable to accumulate small variations found in elevations of original benchmarks. In these instances, levels must be corrected before proceeding (see an example).
Payment for Class A excavation is usually based on plan quantities, so pre-construction cross sections are generally not required. However, the original plan cross sections are checked for accuracy while setting slope stakes. If they are found to be reasonably accurate, the original sections may be used if recomputed quantities in any balance become necessary. If a one-foot average deviation is found in the original cross section, new shots are taken and used in lieu of the plan section to compute the new excavation quantities. Elevations are established to the nearest one-tenth of a foot. Distance from centerline need not be closer than the nearest one-half foot. The contractor is notified in writing when a revision in excavation quantities is anticipated due to errors in ground elevations, change of grade, or typical section. An example of cross section notes is available.
The principles described in the paragraph above (EPG 238.4.1.15) also apply to channel changes and channel cleanouts where quantities have been computed. Since plan quantities are not used to pay for borrow excavation, borrow areas must be staked and original cross sections taken before the contractor begins work in the area.
If rock is encountered, the rock area is cross-sectioned as soon as overburden has been removed. In case of extreme variation of the rock surface (i.e. pinnacle formation) where a line of demarcation between rock and earth cannot be established, the area engineer, resident engineer, and contractor's representative must agree as soon as practicable on a percentage factor of rock classification for this area. The Construction Division is advised so a field liaison engineer may be present when percentage factors are determined on large areas. This method of classification is only used when it is impossible to establish lines of demarcation. Any decision must be confirmed by letter or documentation record.
Shots are taken on the exposed rock surface. After rock has been excavated, and before any backfill is placed, shots are taken on the “new” rock surface to show the lower limits of rock excavation. It is not necessary for the rock broken below limits required for undergrading to be completely removed from the lower portion of cuts prior to taking the shots. However, the broken rock must be sufficiently removed to expose an area of at least one-half the width of the cut so shots can be taken. After collecting the data from this half, the remaining half must be similarly exposed and shots taken. Once entered in the computational software, final rock sections are taken at the locations where original rock cross sections were taken, plus any additional sections needed to arrive at the correct volume of rock excavation.
As soon as practicable after completion of any part of the work, the final surface shots are taken where required for computation of final pay quantities. The final surface shots extend beyond the original surface limits to produce a tie point between original and final surfaces. Low lying excavation areas which might be materially altered by high water or overflow (channel changes, borrow pits, etc.) are cross-sectioned immediately after excavation is completed. These sections must be taken at exactly the same stations where preconstruction sections were taken.
Slope stakes are an important part of the staking job as they control lines and grades to which the grading contractor will work. Gradeline, typical section, and roadway cross sections are studied to be entirely familiar with the section involved before staking starts. The grade to which the road is to be constructed is computed for each station, and each half station on sharp vertical or horizontal curves, and as needed in rock cuts and other locations. The grade line is a system of tangent lines with parabolic curves at the intersections. Tangent grade is shown as a percentage, such as 4.50%, which means 4.5 ft. rise or fall per 100 feet. Going with the stationing, the ascending grades are marked plus, and the descending grades are marked minus. The vertical curves are shown in lengths (i.e. 200 ft., 300 ft., etc.). Before manually computing vertical curve corrections, check tangent grades by starting at the first intersection of tangent grades near the beginning of project. Computation of grade elevations on a summit vertical curve with tangents of equal lengths is shown in Figure 5. A vertical sag curve is computed in a similar manner except that the offset is added to tangent grade instead of being subtracted. The survey data collector is used for quick and accurate determination of offsets and elevations.
Examples of slope stake notes and the location, and marking of stakes are available. Slope stake elevations are read to the nearest 0.1 ft. Distances are measured to the nearest 0.1 ft. All work is checked for errors by comparing slope stake distances as computed in the field against cross sections in the plans.
There are several satisfactory methods of showing information on slope stakes. The intent is to provide the contractor with the following information:
This is the minimum information to be shown on a slope stake. Additional information may be shown, but it is not to be overdone to the point of confusion. The documentation record explains the stake markings.
Slope stakes are set on all volume grading sections at each station (100 ft) and at any plus station where they may be necessary due to curvature or rough topography. On sections of work that have varying slopes, it is beneficial to indicate the slope on each stake in addition to the other markings. Slope stakes are not set for linear grading.
Slope stakes are also set for channel changes and special ditches where there is a grade and typical section. Slope stakes may be necessary in borrow pits that are excavated to certain grades. Slope stakes are not always necessary for road approaches; however, they are set where special grades are designed.
Where rock is encountered, new slope stakes are set on top of rock for the rock slope as shown on the typical section or as determined by redesign. Care is taken to assure that the same proposed grade used for original staking, except in the case of redesign, is used when setting subsequent lines of slope stakes.
Shoulder elevations can be computed using the survey data collector, computational software on the computer or manually. On tangents where both shoulders are of equal elevation, shoulder elevations are calculated by applying a constant difference to profile grade. On curves, grades of shoulders are not equal due to superelevation. The amount of superelevation for the various curves is shown on Standard Drawings 203.20 and 203.21. Elevations of each shoulder must be recorded in the slope stake book along with any ditch and slope information that may be designated on roadway cross sections.
Finished grade stakes are used to check not only earth subgrade but also finished grade of aggregate base and final roadway surface grade. Finished grade stakes are also needed on grading work of projects where stage construction is used, with paving to be done on a later project.
Finished grade stakes are generally set at 50 ft intervals offset from the edge of pavement or shoulder, and are marked with a cut or fill amount to finished pavement grade. The contractor is consulted to determine the amount of required offset, if any, and whether any additional finished grade stakes are desired. It may be necessary to set them at closer intervals in some cases due to abrupt alignment, steep grades, and spiral transition curves. All elevations are to be determined and markings for cut or fill are to be made to the nearest 0.0l ft. It is not necessary to set finished grade stakes in linear grading sections.
OpenRoads Designer is a comprehensive software package that covers every construction phase from staking through final plans. The software works with the MicroStation graphic environment to provide dynamic on screen visualization for the user. OpenRoads Designer chains and cross sections created by Design can be exported directly to HP48/SMI for staking. Using OpenRoads Designer can ensure consistency and accuracy of construction and generate significant time savings in the overall effort of staking and payment calculation. Guidelines for the use of OpenRoads Designer applied to construction processes are provided in the Construction CADD Manual.
A detailed study of plans is made to become thoroughly familiar with each structure before staking begins. All bridges have separate plans showing dimensions, elevations, and other information necessary for staking the bridge. An error in staking a structure will not occur if the staking procedure is thoroughly checked and some form of verification is used.
Field notebooks for structures are prepared in advance and all necessary data placed in the book so it will be available when staking begins.
Culvert books are prepared by using a separate page for each structure. Show station of structure, type, size and length. Staking diagrams, showing all dimensions and staked distances, are made. Include a sketch showing elevations of flow lines. This information is taken from culvert plans that show station, size, type, length and skew angle. Leave space for sufficient cross sections and elevations to ensure properly computed structure excavation when required. Cross sections in the plans indicate the length of culvert each side of centerline and flow line elevations. If the culvert is a corrugated metal pipe, the length is to the ends of the pipe. If the pipe is a concrete pipe with flared end sections, the length includes a portion of the end section. The length of a concrete box culvert is to inside faces of headwalls. Additional information can be found on Standard Plans 731.10 and 732.00. The “angle” of the culvert is shown as 90 degrees if at right angles to the centerline, or a certain degree skew from right angles if other than 90 degrees. The skew is written RA or LA, meaning right ahead or left ahead. Right or left is determined by the direction of increasing station.
Generally 2 hubs centerline are all that are required to establish centerline for a pipe culvert. Set one hub at each end and offset a definite distance from the end of proposed pipe. If there is a break in the flowline grade, set 2 hubs - one right and one left of culvert centerline at the break, to mark this location. From the nearest benchmark determine the elevation of the top of each hub and compute the cut or fill from it to the respective flowline point. Set a guard stake behind each hub marked with its identity, offset distance, and cut or fill to the flowline elevation.
The culvert as designed is checked during staking to see that it fits existing conditions. In most cases it will be found that the culvert as planned will function satisfactorily. It is not intended to encourage habitual revision of culvert plans but when occasional revision is necessary, it is made as early as possible. Collect sufficient data for computation of revised excavation quantities if justified by a change in location or flowline elevation. Usually, a single section along the culvert centerline is sufficient, but if additional sections are necessary, they are to be taken parallel to culvert centerline.
Concrete box culverts are staked using the same method used to stake pipe culverts except additional stakes must be set for the inside face of each headwall. A stake marked "inside headwall" is set well beyond the construction limits on each side of the culvert, with a tack for line.
The box culvert as designed is checked against existing conditions, as earlier discussed. Remember that changes are to be avoided if possible. If a revision of the flowline elevation appears warranted, it must be determined whether commitments have been made to agencies or individuals outside MoDOT concerning the flowline elevation as designed before any changes can be made. A culvert, classified as a bridge, is not to be changed in any respect without prior approval by Divisions of Construction and Bridge.
Bridge field notebooks are prepared in a manner similar to that used for culverts. A separate page is used for each bent of the structure, with the staking diagram showing required dimensions and staked distances. A sketch showing an elevation of the bent together with critical elevations is included. The left hand page of the book is used for recording required level data.
Typical MoDOT practice is to stake and reference only those centerlines and layout lines used as dimensional references on the plans. These lines include the following:
Specific structure element locations such as piles, edge of footing, end of wall or other details that can be located from staked lines and plan dimensions are not to be staked. These are established by the contractor and checked by MoDOT personnel.
Station numbers shown on the plans are the stations at the ends of bridge, usually at the fill face of the end bents. At least 2 substantial tacked hubs are set well past each end of the bridge, preferably on high ground that will not be disturbed during construction. This gives 4 points on centerline of bridge. If one is lost or destroyed, the line may still be recreated. From the station at the end of the bridge, location of the first bent or abutment can be determined. The work line for end bents is generally the fill face. At least 2-tacked hubs are set on each side of the bridge clear of all construction activities, for each pier, bent, or abutment and on each side of a footing.
Bridges over wide expanses of water may require the use of triangulation to fix the location of water piers, and to determine exact location of substructure units on the landfall ahead. Triangulation is accomplished in a manner set forth in any recognized survey handbook. EDM equipment may be used to accurately locate mid water piers directly without the use of triangulation net works.
A good benchmark that will not be disturbed is established at each bridge site. Elevation of this benchmark must be thoroughly checked. It is used to set all control elevations at the bridge. After staking is complete, each footing it laid out and sufficient ground elevations are obtained to compute structure excavation quantities. Grades are set to show elevation of the bottom of footing as noted on the plans. A guard stake is set by each hub. This includes accurate written information regarding the hub, what point or line it marks, the offset distance, distance to grade and other necessary data.
A thorough check of all measurements, angles and elevations must be made to ensure no errors exist. Persons, other than those who did the original staking will checking these measurements using different methods if possible. Always be certain the staking is correct and check the plans for errors.
It is important to preserve all land monuments of section corners, subdivision corners and all U. S. Government monuments within the right of way. All engineers and surveyors use these markers. It is MoDOT policy to cooperate in their preservation. An examination of plans is made for the location of section lines or subdivision lines crossing or intersecting other such lines within the right of way. Plans may also indicate land monuments. Office notations are made in field notebooks of indicated monuments and land line intersections so locations may be investigated for existing monuments.
All monuments that will, or may, be disturbed by construction operations must be referenced and re-established by a professional land surveyor. Forms and instructions for surveyors may be obtained from the:
Missouri Land Survey P. O. Box 250 Rolla, Missouri 65401
MoDOT employees who are professional land surveyors may be used where feasible. Employees who are not registered will not do the referencing or re-establishment of corners. If it is to MoDOT’s advantage, it is permissible to use independent professional surveyors.
A U.S. Geological Survey monument may serve as both a level monument and a traverse monument. If it becomes necessary to move one of these monuments, immediately notify:
United States Geological Survey, MCMC l400 Independence Road, MS-800 Rolla, Missouri 65401 Telephone No.: 573-341-0940
In the notification, give a general description of the area in which the monument is located, together with the designation stamped on the bronze plate. The U.S.G.S. will either send a party to move it, or send forms on which to enter the description of the new location and field notes for revision of data. If project forces move a level monument, the difference in elevation only need be recorded with proper field notes to substantiate the difference. To preserve accuracy as nearly as possible, the difference in elevation is given to the one-thousandth of a foot. For a traverse monument, the determined data is true bearing to the nearest l/2 degree, with horizontal distance to the nearest one-tenth foot from old to new location. Where true bearing is not available, reference the monument with some accurate transit ties so exact location can be re-established. Send this information to U.S.G.S. so they can reset the monument with their own forces.
At times the plans for an improvement project may require the contractor to provide the necessary surveying and staking for the successful completion of their work.
When this occurs, staking must be done in accordance with general accepted surveying practices and provisions contained in the contract. The requirements contained in this article may be used as guidance.
The contractor will preserve all right of way monuments, benchmarks control points and reference marks set in the field. If any monuments are damaged, destroyed or disturbed by the contractor, the cost of replacement will be at the contractor’s expense and will be deducted from payment for the work.
All surveying by the contractor will be documented in a written form acceptable to MoDOT’s resident engineer. During performance of the work, all surveying documents must be available and supplied to the resident engineer upon request, at the contractor’s expense. All documents will be labeled with the route, state job number, county, contractor name, survey party supervisor and date.
The resident engineer will furnish and set control points with known coordinates. The resident engineer will furnish all coordinate data to layout the job and locate benchmarks as shown on the plans. The contractor will provide all other staking necessary for the successful completion of the work. All alignment control established by the contractor must be referenced, and a copy furnished to the resident engineer.
The resident engineer will perform any surveying or measurements necessary for computing pay quantities. The contractor will notify the resident engineer at least two working days prior to disturbing any areas used to calculate pay quantities.
All surveying work performed by the contractor must be sufficient and accurate to construct the work in accordance with the contract documents. Any delays or additional costs to the project that result from insufficient or inaccurate staking or time lost for corrective action will be considered a nonexcusable and noncompensable delay.
The construction centerline shown on the plans must be accurately established and the control points of all curves will be referenced. If it is necessary to introduce an equation in order to match the plan stationing or if a plan equation is changed, the change will be at the written direction of the resident engineer.
Adjustments necessary to provide accurate staking or match improvements to existing features shall be immediately brought to the attention of the engineer. The engineer will determine the nature of the discrepancy and make revisions to the plans as necessary. The contractor shall perform any restaking required by such revisions. Any reimbursement due to the contractor for additional staking due to design errors will be in accordance with Section 109.4.3 of the Missouri Standard Specification for Highway Construction.
After the centerline has been established and referenced, centerline elevations will be taken at all stations and at any other points required to ensure the computation of accurate quantities. Centerline elevations will be based on the plan datum. All benchmarks shown on the plans will be checked.
In the event a difference of plus or minus 0.01 ft exists in elevation for any benchmark shown on the plans, check levels must be run and shown in the notes. The elevations will be corrected to plan elevation at each benchmark where any difference occurs, and will be noted in the field notes. If a plan benchmark has been disturbed or if correction of the plan elevation is not feasible, a full explanation must be made in the notes. The contractor will furnish the resident engineer a listing of benchmarks prior to beginning construction.
If original plan cross sections differ from existing conditions by an average deviation in excess of one ft, the contractor must immediately notify the engineer. The resident engineer will be responsible for taking cross-sections where deviations are determined to exist.
After completing any bridge, box culvert or retaining wall staking, the contractor will furnish the resident engineer structural layout plan sheets that show the location of all points that have been staked. At the time of furnishing the marked layout sheets, the contractor will meet with the resident engineer a minimum of two working days before construction begins to review the layout.
Upon completion of the project, the contractor will provide the resident engineer all original surveying field notes, layouts and computations in standard bound survey notebooks or in an acceptable form.
All surveying and staking work performed by the contractor as part of the construction contract will be paid for at the contract lump sum price. It will be considered full compensation for the following:
Payment for contractor furnished surveying and staking completed, not to exceed the contract item amount, will be made upon written request by the contractor. This request must be submitted to the resident engineer two business days prior to the progress estimate date.
Complete payment will not be made until the contractor has provided all of the original surveying field notes, layouts, computations and notebooks to the engineer.
When a bid item for construction surveying is included in the contract, the contractor will provide the necessary surveying and staking for the successful completion of the work in accordance with Section 627 of the Missouri Standard Specification for Highway Construction.
The contractor’s surveyor is expected to perform the staking required by the contract. MoDOT surveyors are not to be used as back-ups if the contractor’s surveyors are unavailable. MoDOT will furnish the contractor’s surveyor with additional working points and benchmarks prior to the beginning of construction if needed. The contractor’s surveyor will make working points available to MoDOT upon request. MoDOT will check all staking of larger structures such as box culverts and bridges (try to give 2-days notice when these will be ready for checking). MoDOT will spot-check the staking of smaller structures, slope stakes and paving grades. If the contractors surveying is outside of tolerance they will be notified in writing to correct it. The contractor is responsible for final line and grade of the end product. The contractor’s surveyor will provide enough information and staking upon request so MoDOT can adequately check the staking on the project. Staking the profile outlined in the Specifications may not be required for each project, depending on the scope of the work. The clearing limits are generally marked 10’ beyond the planned slope line to allow for grading and the adjustment of slope-stakes to fit original ground. MoDOT will survey everything directly related to pay. The contractor will maintain adequate working points during and after construction (working points may be needed for staking R/W after construction is completed). The surveyor is considered a subcontractor with the same requirements of any subcontractor with the exception of certified payrolls. This work is considered a non-regulated job so no prevailing wage rates are required. Utilities that may have to be staked will be done by MoDOT or will be considered additional work by the contractor with additional compensation. These guidelines are further described as the pre-construction checklist.
When surveying and setting construction stakes is the responsibility of the resident engineer, the contractor will give the resident engineer reasonable notice of their intent to perform work in a particular area of the project in order to afford the resident engineer sufficient time to set construction stakes establishing lines, slopes and profile grade. For roadway work, the resident engineer will set construction stakes establishing lines, slopes and profile grade and will furnish the contractor with all necessary information relating to these lines, slopes and grades. These stakes and marks will constitute the field control by and in accordance with which the contractor will establish other necessary controls and perform the work. For structures, the resident engineer will stake and reference those centerlines and layout lines used as dimensional references on the plans and will provide a benchmark at each structure location. The resident engineer will provide and mark haunching information for the contractor's use in forming of all bridge decks. The contractor will provide all other lines, locations, alignment, grade elevations and any other necessary controls by use of engineering instruments or other tools or methods as required to build the structure.
The contractor will preserve all stakes and marks, and if any of the construction stakes or marks are destroyed or disturbed the cost of replacing them may be charged to the contractor by deducting the cost from payment for the work.
The contractor will furnish and deliver at their expense the size, quality and quantity of stakes required by the resident engineer. If the stakes have not been delivered at the time and place required for use, the resident engineer may purchase the stakes and deduct the entire cost from any payment to the contractor.
Upon the written request of the resident engineer, the contractor will furnish assistance as may be necessary for the purpose of making measurements and for driving stakes. The Commission will reimburse the contractor by regular payment estimate for assistance by the contractor's employees that was requested in writing by the resident engineer prior to its actual performance.
The resident engineer will perform surveying and setting of construction stakes except when a bid item for this work is included in the contract.
Quality assurance checks by MODOT do not relieve the contractor of their responsibility to construct the project to the specified lines and grades. MoDOT checks are to identify any contractor staking errors to minimize any adverse impacts to the project. They are also to help spot any plan errors.
All equipment used to verify the contractors methods and/or stakes must be independent equipment using project files generated from MoDOT design data, or in the rare circumstance that an Alternate Concept or Value Engineering proposal has been approved, the data supplied by the contractor’s engineer. Under no circumstance should equipment rented, borrowed or loaned to MODOT by the contractor constitute an independent check.
The MoDOT construction inspector and the contractor responsible for surveying activities on the project should discuss procedures of localization and calibration with the MoDOT design surveyor.
The following guidelines can be used when performing quality assurance checks:
A quality assurance check should be performed on all control points including the control established by design survey. The inspector responsible for surveying activities should establish additional control points within sections of a project where existing control will be destroyed during construction operations. Before checking the accuracy of a control point, the project inspector should visually inspect the point to ensure that it is installed according to EPG 238.3.17 or EPG 238.3.18. The point should be placed in an area capable of acquiring satellite signal for the purpose of GPS base setup. The quality assurance check should be within 0.04 ft. horizontal tolerance. The elevation on a 3D control point should be compared to that of nearby benchmarks. The vertical tolerance for a 3D control point shall be 0.01 ft.
A survey of the clearing limits for quality assurance purposes may not be necessary since most are designated by marking existing vegetation with marking tape. However, a brief inspection of the clearing limits should be performed. The inspector should ensure that the clearing limits were calculated properly and do not go beyond the limits of the right of way.
Checking template at 500 ft. intervals is sufficient. Greater or lesser intervals may be considered if agreed to by the contractor and RE based on the conditions of the project. Catch points should be within 0.2 ft. horizontal and 0.1 ft. vertical as well as each break in the template. Ditch grades should allow proper drainage. The vertical tolerance for ditches with grades less than 0.1% should be 0.05 ft.
If GPS machine control is used in lieu of conventional staking to construct the project, the inspector should record random shots taken with either a GPS/RTK or Total Station using properly configured project files. These shots would be used to compare the data from the field to the plan cross-section to determine whether the project is being constructed correctly. If the software in the data collector does not utilize full width templates, the recorded shots may be compared manually by calculating plan grade utilizing the same methods used for slope stake calculation.
When using machine controlled grade, the cross-section should be checked at certain odd locations, such as between break points of the templates, to determine if the software is interpolating between cross-sections properly. Good locations for this determination include vertical curves and super elevation transitions. The interpolation shall be based on the horizontal control and profile grade, not a straight line distance between template points.
A visual inspection should be performed of the staking at each and every drainage structure before construction to verify if the alignment and grade properly matches the stream or drain. The vertical alignment should never be adjusted without consulting the design engineer or project manager. If the structure is an extension to an existing the grade should be checked against the existing structure to ensure proper drainage. The project inspector should check at least 15% of the pipe or culvert stakes on the project. More checks may be considered if problems are found during the initial check. Staking tolerances should vary according to application. The vertical grade should compare within 0.1 ft., yet a slope ensuring proper drainage is to be verified for relatively flat slopes.
Quality Assurance checks of the location of a bridge or bridge culvert should be within 0.1 ft. of plan location. Any stakes checked for the structure shall compare within 0.01 ft. of the remaining stakes for that particular structure. Any vertical or horizontal grade stake for a bridge structure should be within 0.03 ft. Inspectors should ensure that stakes detailing end bents are labeled correctly and staked at the fill face, not the centerline of the bent. The inspector should also verify that centerline stakes are properly labeled as to centerline structure or centerline roadway.
Written documentation should be produced detailing the staking scheme to assure the surveyor, paving contractor, grading contactor and inspectors are in concurrence. The project inspector should check a minimum of 10% of the paving stakes. The inspector should check the grade line at random locations, checking several consecutive stakes at each location. Quality assurance tolerances should be 0.1 ft. horizontal and 0.04 ft. vertical with only a 0.01 ft. vertical difference between consecutive stakes. The engineer shall approve any adjustment to vertical grade in order to meet existing pavement or a bridge structure. Vertical grade adjustments should not be greater than 0.04 ft. per 50 ft.
If the contractor chooses to construct pavement by stakeless method, the quality assurance inspector shall verify location and grade of finished base material or finished pavement. Thickness of base material and pavement are verified by QC/QA specification as well as pavement smoothness.
If the quality assurance checks do not compare within tolerance, the inspector should review the documentation submitted by the surveyor to determine the methods used for the staking. The field notes or electronic raw data files should be reviewed for obvious errors. If the error remains uncertain, then the stakes should be checked with a third instrument.
If the project is constructed by GPS machine control and a comparison is not within tolerance, the system localization should be checked on a control point. If the systems show the same XYZ for a specific point, then the proposed grade should be checked against the cross-sections to determine which system is in error.
If it becomes necessary to set or reset any marking that occurs on a MoDOT boundary line that separates MoDOT owned property from property owned by others, this marking must be performed under the supervision of a professional land surveyor (PLS). Construction staff identifing this need should contact their district land survey manager for assistance.
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