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    SECTION 02570

    INSTRUMENTATION MONITORING SYSTEMS AND SURVEYS

   PART 1 - GENERAL

   1.01 SECTION INCLUDES

    A. Furnishing, installing, monitoring, reading, interpreting data, maintaining and removing geotechnical instrumentation used during open cut, cut and cover, and tunnel excavation operations. Data will be collected and interpreted by the Contractor and furnished to the Engineer as described herein. All data and its interpretation will be made available to the Engineer.

    B. The purpose of the monitoring systems specified herein is to monitor ground behavior and to provide a timely warning for the implementation of remedial measures to prevent possible damage to structures, equipment and utilities.

   1.02 RELATED SECTIONS

    A. Section 02220 - Structural Excavation and Backfilling.

    B. Section 02221 - Excavation, Trenching and Backfilling for Utilities.

    C. Section 02750 - Tunnel Excavation for Interceptor Sewers.

   1.03 SUBMITTALS

    A. Within 15 days of receipt of Notice to Proceed, the Contractor shall submit the qualification of the personnel specified herein; the proposed schedule and procedure for installing instruments and for performing the other work of this section.

    B. Manufacturer's information on each instrument type proposed for use, including calibration and monitoring procedures and samples of typical data calculations; materials and mix proportions for bentonite-cement grout and cement grout, when required; and the manufacturer's recommended procedure for the installation of each instrument.

    C. All submittals shall be provided to the Engineer at least 15 days before beginning work and must be approved by the Engineer prior to installation of any instrument or survey/roadway markers. Geotechnical instrumentation shall not be installed until all submittals specified herein and required prior to installation of instrumentation have been received and reviewed by the Engineer and at least one copy of each submittal has been returned to the Contractor.

    D. Field Boring logs for all instrument installations shall include a concise and accurate description of lithology, weathering and any natural discontinuities including joints, shears and in-filling. In addition, recovery and rock quality designation (RQD) shall be included on the boring log.

    E. After the instruments have been installed, the Contractor shall submit updated working drawings showing the installed location of each instrument identification number, installation date, instrument installation station and offset, and tip or sensor elevation and instrument length, if applicable. Working drawings shall also indicate details of installed instruments, accessories and protective measures, showing fully all dimensions and material used.

    F. Submit as specified in PART 4.0, the pre-construction assessment reports on buildings and other structures within 75 feet of the tunnel alignment centerline and the closest edge of the access shafts.

    G. Monitoring Documentation

    1. Submit proposed forms to be used for recording observations, monitoring and reporting of data. Submit a sample showing proposed format for recording of readings, calculations, and plots.

    2. Submit within 12 hours after monitoring any instrument to the Engineer the following:

    a. A copy of the data sheet containing a cumulative history of all readings, including weather conditions at time of each reading.

    b. A copy of the plot of measured values versus time, which also incudes a time history of construction activity likely to influence such readings (e.g. depth of excavation, location of tunnel bore, presence of heavy equipment)

    3. Submit weekly a brief narrative of instrumentation activity of the preceding week in a format approved by the Engineer.

   1.04 QUALIFICATIONS

    A. Preconstruction assessments shall be done by a recognized authority in this field retained by the Contractor.

    B. The Contractor shall retain a Geotechnical Consultant to design, install, and monitor the instrumentation systems specified in the Contract Drawings and Specifications.

    C. All survey monitoring shall be done by public surveyor licensed in the State of Tennesse and retained by the Contractor.

    D. The subcontract companies and individuals performing the instrumentation work shall be subject to the Engineer's review and approval.

   1.05 NOTIFICATION

    A. The Contractor shall notify the Engineer at least 5 days before the planned installation of any of the instrumentation or prior to grouting existing boreholes specified herein.

   1.06 ACCESS TO INSTRUMENTATION

    A. The Engineer shall have access to all instrumentation installed by the Contractor and shall have access to and use of equipment used to read the instrumentation to allow the Engineer to make periodic readings of the instrumentation.

    B. The Contractor shall provide access to the work for such independent installations and shall protect said instrumentation from damage due to his construction activities or those of his subcontractors.

   1.07 DESCRIPTION OF INSTRUMENTATION SYSTEMS

    A. Convergence Measurement Tape Extensometer System:

    1. Convergence Reference Section - An array of convergence reference points located within the same plane. These points should be located at the top, bottom and springline of the tunnel liner at 500 foot intervals.

    2. Convergence Reference Point - An anchor consisting of a specially threaded bolt.

    3. Tape Extensometer - A precision instrument for measuring distances between convergence reference points.

    B. Inclinometer Casing

    1. A casing will be installed within vertically drilled boreholes to selected elevations. A sensor shall be lowered within the inclinometer casing to periodically measure lateral ground movements at shaft locations.

   1.08 DESCRIPTION OF SURVEY MONITORING SYSTEMS

    A. Settlement Probe - Rebar placed and grouted within borehole installation to monitor deep subsurface settlement, See Detail on Exhibit 1.

    B. Wall and Column Marker - Marker established on bridge columns and fences to monitor settlement and lateral column and wall (horizontal and vertical control monitoring). See Contract Drawings for locations.

    C. Survey Marker - Surface Survey Marker established at Inclinometers and Settlement Probes to monitor instrument movement and settlement. See Contract Drawings for instrument locations.

    D. Ground Surface and Roadway Settlement Markers to be established at each baseline station noted in 1.9C to monitor settlement at ground surface. Markers to be established at centerline, and approximately 10-foot spacings for a distance of 50 feet on each side of the centerline.

   1.09 INSTRUMENT LOCATIONS

    A. Inclinometers at the following shaft locations:

    SHAFT NO. STATION OFFSET

    B. Convergence - At 500 foot centers along tunnel section.

    C. Ground Surface - Roadway Settlement Marker Locations every 200 feet along the tunnel section of the alignment. Between sewer stations 77+00 and 85+00 roadway settlement markers shall be located every 100 feet. In addition, the survey line locations are required on one shoulder of each railroad, highway and road crossed by the tunnel, and at each settlement probe location.

    D. Settlement Probes at the following locations:

    TIP ELEV. STATION OFFSET

    E. Horizontal and Vertical Survey Monitoring at the following locations:

    STATION OFFSET

   1.10 ACCEPTABLE TOLERANCE FOR INSTRUMENTATION LOCATIONS

    A. All instruments, settlement probes and markers shall be installed within one foot of the locations specified herein or as shown on the Contract Drawings unless movement of the instrumentation is required by a.) the Engineer, b.) underground or overhead obstructions, and/or c.) construction excavations. Specific locations shall be approved by the Engineer.

    B. Utilities in close proximity to the instruments and settlement probes shall be uncovered and tied in with surveyed coordinates to allow installation of all instruments and settlement probes at the specified location (or as close as possible, offset only to provide safe clearance of underground utility lines).

   PART 2 - PRODUCTS

   2.01 MATERIALS

    A. Each instrument specified herein is to be the product of an acceptable manufacturer currently engaged in manufacturing geotechnical instrumentation hardware of this type.

    B. Tape Extensometer System

    1. Convergence Reference Points: Measuring bolts made of ripped steel with galvanic surface protection with threaded stainless steel measuring stop. Provide Type KV 20/250 manufactured by Geotechnical Instruments, Inc. or approved equal.

    2. Calibration Frame: Provide a rigid member compatible with the tape extensometer. Clearly identify the frame and secure it loosely to support brackets in the tunnel to prevent it from being disturbed or damaged by construction activities and to allow free movement due to temperature variations.

    3. Tape Extensometer Unit: Provide two units, with protective carrying case, Model KM 15 manufactured by Geotechnical Instruments, Inc., Gaithersburg, MD, or approved equal.

    4. Provide protective coverings for each convergence reference point to protect from damage due to construction operations and adverse environmental conditions. In streets, the protective casing shall be rated for high traffic applications.

    C. Inclinometer

    1. Casings and Couplings: Casings shall be made of thick wall PVC plastic, the non-telescoping type. Couplings shall be made of the same material with a nominal outside coupling diameter not greater than three inches. The casing shall be fitted with a bottom cap and a top cap; however, the top cap shall not be considered as adequate protection for the inclinometer casing. Casings shall be furnished in lengths of ten feet and capable of supporting the weight of 50 feet of inclinometer casing freely suspended inside a drill hole. Wall thickness shall be sufficient to withstand external ground pressure and have sufficient flexibility to accurately reflect horizontal ground movements. Casings shall have four internal broached longitudinal keyway grooves spaced 90 degrees apart with a tolerance equal to or less than one degree in ten feet that are compatible with the inclinometer sensor and external alignment groove. Couplings shall be compatible with casing and have internally broached alignment groove and keyways. Non-telescoping couplings shall be used.

    2. Inclinometer Sensor: The sensor shall be water proof and shall be compatible with the inclinometer casing. The sensor shall have a 2 feet gauge length and shall be capable of measuring the angle of inclination in two orthogonal directions. Provide Geotechnical Instruments, Inc. Torpedo INS 4.1A or approved equal.

    3. Provide one manual readout unit Geotechnical Instruments, Inc., Model INS 5.1 and a Model INS 5.2 Inclinometer Data Logger unit with operating software or approved equals.

    4. Cable: Cable shall be a minimum of 150 feet in length, waterproof, and compatible with sensor and readout unit. The cable should have permanently affixed divisions of feet and inches. Suitable cable reels and grips shall be provided.

    5. Protective Coverings: Provide lockable traffic rated watertight protective coverings to protect from traffic, construction activities, vandalism and adverse environmental conditions.

    D. Settlement Probes

    1. Probes: The settlement probe shall consist of No. 4 rebar. The probe shall be encased in casing. See Exhibit 1 at end of this Section for detail. See 1.9D and Contract Drawings for locations.

    2. Casing: Casing shall consist of one inch diameter PVC plastic pipe.

    3. Protective Covering: Provide traffic rated watertight protective coverings to protect from traffic, construction activities, vandalism and adverse environmental conditions.

    E. Survey Monitoring Markers

    1. Settlement wall markers, survey markers and roadway markers shall consist of suitable survey pins installed flush with pavement surface. Pins in concrete shall be installed in predrilled holes to avoid spalling of concrete. Markers installed in unpaved areas shall consist of No. 4 rebar driven a minimum of three (3) feet below ground surface. Top of bar to be flush with ground surface. The survey points shall not be painted except where approved by Engineer. 

    2. All Wall Markers, all bridge Column Markers and all Settlement Probes shall consist of survey pins engraved with cross hairs and shall be suitable for accurate horizontal and vertical control monitoring. Required accuracy to be + 0.01 feet for all horizontal and vertical control monitoring.

    F. Benchmarks

    1. Existing benchmarks indicated on Contract Drawings may be used as reference during survey monitoring provided benchmarks are at least 100 feet from edge of tunnel or shaft. The same benchmark used to initialize each survey monitoring point shall be used throughout the entire construction operation.

    2. The benchmark to be used for each set of markers shall be identified on data submittal sheets.

   PART 3 - EXECUTION

   3.01 GENERAL

    A. This part shall include the placing of all specified materials at the locations and elevations as shown on the Contract Drawings or as established by the Engineer.

    B. The work performed hereunder shall conform in every respect to the Contract Documents, the applicable City requirements, the applicable local ordinances and sanitary codes, the regulations of the State Health Department, the regulations of the Occupational Safety and Health Administration (OSHA) and the regulations of the Environmental Protection Agency (EPA).

   3.02 REMEDIAL MEASURES

    A. The Contractor shall institute remedial measure required based on results of instrumentation and general observation including modifications of construction procedures if necessary.

   3.03 EMERGENCY MEASURES

    A. Whenever there is a condition which is likely to endanger the stability of the excavation, adjacent structures or utilities, as indicated by the instrumentation data or by visual observations, the Contractor shall operate with a full crew on a 24 hours a day basis, including weekends and holidays, without intermission until those conditions no longer jeopardize the stability of the work.

   3.04 INSTRUMENT ACCESS

    A. The Contractor shall provide and facilitate safe access to all instruments for the Engineer including ladders, mechanical truck mounted working platforms with operator and all other necessary labor and facilities, and removal thereof. Work shall be scheduled in a manner to permit the Engineer to perform readings safely as required.

   3.05 EXISTING WATER WELLS

    A. Water levels shall be recorded in all existing water wells within 500 feet of the sewer alignment.

    B. Water level readings in the water wells shall be made before construction begins, quarterly, and after completion of construction.

   3.06 INSTRUMENT INSTALLATION

    A. A professional engineer or engineering geologist, with a minimum of two (2) years experience in the installation of the instrumentation specified in this section, shall be responsible for instrument installation and rock core logging.

    B. The Contractor shall submit an instrumentation and initialization schedule within 21 days after receiving notice to proceed. Inclinometers shall be installed at least 14 days prior to excavation of the tunnel shafts. Settlement probes shall be installed at least 21 days prior to the advancement of the tunnel bore within 100 feet of the probe. Survey points shall be installed at least three (3) days prior to the open cuts or when tunnel excavations are within 100 feet of the survey markers.

    C. Instrument Locations: Instruments shall be installed at tentative locations shown on the Contract Drawings or as directed by the Engineer. Actual instrument locations shall be approved by the Engineer after existing underground utility lines and any other existing underground construction have been located and cleared by the Contractor and the limits of the proposed shaft excavations have been established.

    D. Method of Installation: Instrument installation shall be in strict conformance with the instructions and procedures of the manufacturer and as detailed herein.

    1. Drilling and Installation of Settlement Probes: The settlement probes shall be installed at the locations indicated on the Contract Drawings and to the depths specified herein unless offset required and approved by Engineer to avoid existing underground utility line or other underground construction.

    Drill a minimum 4 inch diameter borehole to the required tip elevation. Case the hole if necessary to prevent caving. Cut rebar so that bar will be a minimum of 3 inches below the ground surface when installed. Grout the bottom 2 feet of the borehole with quick setting, non-shrink grout. Install the rebar vertically in the center of the borehole and hold stationary until grout sets.

    After grout is set, pour in approximately 9 inches of sand around the rebar. Install 1 inch PVC pipe over rod making sure 3 to 4 inches of rebar sticks up over casing. Pour sand around outside of PVC casing up to a depth of about 4 feet below the ground surface. Grout the next 3 feet of the borehole with a lean cement-bentonite grout. Install protective covering such that the top of the rod is a minimum of 3 inches below the cover. A detail of the installation is shown on Exhibit 1.

    2. Installation of Convergence Reference Points: Drill four holes 10 inches deep at the crown, bottom and left and right spring lines at about 500 foot intervals along tunnel following completion of tunnel excavation at each location. Holes shall be drilled a minimum of 0.5 inches larger than the bolt and the bolt secured in place using quick setting epoxy. Bolt shall be set flush with the rock surface and affix protective cover.

    Maintain access to the reference point by providing a blockout to create a recess in shotcrete or tunnel liner where applicable and required by the Engineer.

    3. Installation of Inclinometer Casing: The inclinometer casing shall be installed at the locations indicated on the Contract Drawings to depths of 15 feet below the bottom of the tunnel shaft. If necessary, the locations may be adjusted to avoid intersection of existing underground utilities or other underground construction. Final location to be approved by Engineer. Use a hole size recommended by instrument manufacturer. Case the hole through overburden into rock using steel casing if required to prevent caving, and remove the casing after installation and grouting of the inclinometer casing. Intermittent sampling shall be performed in the overburden soils while the rock formation shall be cored continuously from the top of rock to the total depth of the inclinometer. Drilling mud shall be used to prevent caving and to keep borehole open until casing is installed.

    The inclinometer casing shall be installed so that the pairs of grooves in the casing are aligned approximately parallel and perpendicular to the centerline of the shaft and to the structure nearest the shaft that could be affected by ground movements. The casing shall be installed as vertically as possible and shall not be inclined more than 5 degrees from vertical.

    The inclinometer casing annulus shall be backfilled with an approved slow-setting bentonite-cement grout mix with a compressive strength between 10 and 20 psi.

   3.07 TOLERANCES

    A. Settlement probes and inclinometer casings shall be installed within one foot of the horizontal location shown, unless offset is required to clear underground utility lines, anchors, etc. or as otherwise directed by the Engineer. Settlement probe tips, and inclinometer casings shall be installed within 0.5 foot of elevations indicated.

    B. Should actual field conditions or existing underground construction prohibit installation at the location and elevations specified in this section, obtain prior approval from the Engineer for new instrument location and elevation.

    C. Establish the initial elevation of settlement markers and settlement probes to 0.005 feet.

    D. Record subsequent elevations of settlement markers and settlement probes to 0.005 feet. Achieve level circuit closure with an error of closure of 0.01 foot or less.

    E. Establish survey turning points so that backsite and foresight are kept approximately equal.

   3.08 INSTRUMENT PROTECTION MAINTENANCE AND REPLACEMENT

    A. Protect and maintain instruments by keeping protective covers locked and watertight. Provide suitable protective barriers around instruments during installation in high traffic or work areas.

    B. Repair or replace damaged or missing instrument components, or entire instruments, as required within five days of notification.

    C. All protective covers in city streets, drives, parking lots, and alleys shall be traffic rated, watertight and approved by the Engineer prior to installation.

   3.09 REMOVAL OF INSTRUMENTS

    A. Prior to final acceptance of the work and subject to review of the Engineer, remove and dispose of the top two feet of inclinometer casings, settlement probes and casings, and the protective covers; plug remaining open portions, if any, with concrete. Backfill casing excavations with grout.

    B. Restore ground surfaces to the condition existing prior to installation of the instruments.

   PART 4 - PRECONSTRUCTION PROPERTY DAMAGE SURVEY

   4.01 PRECONSTRUCTION ASSESSMENT AND PROPERTY DAMAGE SURVEY

    A. The Contractor will perform a pre-construction assessment of all structures within 75 feet of the tunnel alignment centerline or the closest edge of the access shafts. Preconstruction inspections shall be made by qualified specialist retained by the Contractor to observe the condition of existing structures and facilities in the vicinity of the work specified herein. The inspections shall include the entire structure located entirely or partially within the distance specified on each side of the tunnel or shaft.

    1. The assessment shall include a reconnaissance of the exterior portions of the structure within 75 feet of the tunnel alignment centerline or the closest edge of the access shafts and identification and documentation of all visible structural and cosmetic defects with written descriptions, photographs, diagrams and measurements including the location, length, spacing and separation width of all visible cracks (hairline width or greater). The assessment shall also establish water levels of water wells used within 500 feet of the tunnel operations or shaft excavations.

    2. Each survey shall be documented in a bound report.

    3. The intent of this assessment is to provide protection against claims and to clearly identify actual damages that may occur during construction.

    4. The Owner will be solely responsible for obtaining access to privately owned buildings for the assessment and for the establishment of instrumentation and survey monitoring points.

    5. Nothing contained herein shall relieve the Contractor of responsibility for claims arising from his construction operations. Failure to inspect any structure, whether or not required by these Contract Documents, or inadequacy of the inspections, shall not relieve the Contractor of his responsibility.

    6. A post construction assessment by the Contractor shall be made to document and note changes in the conditions of the structures surveyed prior to construction.

   PART 5 - CONSTRUCTION MONITORING

   5.01 FREQUENCY OF SURVEY MONITORING

    A. The elevations of all survey markers and roadway markers shall be established in accordance with the following schedule unless otherwise directed by the Engineer.

    1. Twenty-four (24) hours after installation. Markers will be approved and considered initialized after two consecutive readings (+ 0.01 feet) are obtained at each monitoring point. Markers must be properly initialized and approved by Engineer.

    2. Daily, while tunnel excavation activity is within 100 feet of baseline station as tunnel approaches baseline station.

    3. Daily, while tunnel excavation activity is within 200 feet of baseline station as tunnel excavation departs or extends beyond baseline station.

    4. Monthly, when tunnel excavation activity is beyond limits specified for daily readings until pipeline is in place.

    5. Final reading after completion of construction.

    B. The elevations and horizontal coordinates (vertical and horizontal control) of all Wall Markers, Column Markers and all Settlement Probe locations shall be established in accordance with the following schedule unless otherwise directed by the Engineer.

    1. Twenty-four (24) hours after installation. Markers will be approved and considered initialized after two consecutive readings (+ 0.01 feet) are obtained at each monitoring point. Markers must be properly initialized and approved by Engineer.

    2. Daily, while tunnel excavation and construction activity is taking place within 100 feet up and down station of the monitoring point. Weekly monitoring shall be continued until the final liner is in place.

    3. Monthly, for six months after final liner is in place.

    Note: If total cumulative wall or column movement in excess of one-eighth inch occurs, the Contractor will be notified immediately. If total cumulative wall movement in excess of one-quarter inch occurs, all tunnel and shaft excavation activities shall cease and the wall or bridge column secured at the direction of, and to the satisfaction of the Engineer.

    C. A Survey Marker is initialized when two consecutive repeatable readings (+ 0.01 feet) can be obtained at all horizontal and vertical control monitoring points. Additional readings shall be obtained at twenty-four hour intervals if repeatable readings are not obtained during the 24 hour initialization.

    D. All horizontal and vertical control monitor readings shall be reported within twenty-four (24) hours. Total cumulative differential movements at any location in excess of one-quarter inch (one-quarter inch differential from initialized reading) shall be reported to the Engineer immediately (same workday). Cumulative movements in excess of one-quarter inch shall require additional survey monitoring to verify adequacy of operations (means and methods).

   PART 6 - MEASUREMENT AND PAYMENT

    A. No separate measurement and payment will be made for work covered under this section. Work and materials covered under this section shall not be paid for directly, but shall be considered subsidiary to the various bid items required to complete the project.

    END OF SECTION