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    SECTION 02570

    INSTRUMENTATION

   PART 1 GENERAL

   1.01 SECTION INCLUDES

    A. This Section includes furnishing, installing, monitoring, reading, interpreting data, reporting, maintaining and removing geotechnical instrumentation used during open-cut, shaft, diversion structure, and tunnel excavation operations. Data will be collected and interpreted by an experienced geotechnical engineer employed 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 program 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 02222 - Excavation.

    B. 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 qualifications of the personnel specified herein; the proposed schedule and procedure for installing instruments and 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. Submittals for all instrumentation 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. The Engineer will promptly review the submittals and respond prior to the Contractor beginning instrument installation. 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 soil types, groundwater levels encountered during drilling, 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 the pre-construction assessment reports on buildings and other structures as specified in PART 4.0.

    G. The Contractor shall prepare and submit a detailed blasting and vibration monitoring plan. Submittals for the blasting and vibration monitoring plan shall be provided to the Engineer at least 15 days before beginning work and must be approved by the Engineer prior to initiating blasting operations.

    H. Monitoring Documentation

    1. Submit proposed forms to be used for recording observations, monitoring and reporting of data at least 15 days before installing instruments. Submit a sample showing proposed format for recording of readings, calculations, and graphic plots for approval by the engineer.

    2. Submit weekly to the Owner and Engineer one copy each of the following after instrumentation is installed:

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

    b. The graphic plot of measured values versus time, which also includes 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 summary of instrumentation activity of the preceding week in a format approved by the Engineer.

    I. Daily Log: Record daily, on an approved form, a log of construction events and observations to include at least the following:

    1. Detailed progress of sewer/tunnel and shaft excavation operations, including bottom of excavation elevation at the end of each day, and location, type, and time of installation of excavation supports.

    2. Tunnel driving progress including stationing of the increments completed and the time of excavation.

    3. Construction loading in the vicinity of the instruments.

    4. Amount and description of the seepage of water, if any is observed in the excavation.

    5. Incidence of extraordinary ground loss, ground water flow, instability, or other unusual events.

    6. Duration and cause of interruptions or delays to shaft or sewer/tunnel excavation.

    7. Temperature, precipitation type and amount, and other environmental factors that may affect instrument readings or results.

   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 blasting and vibration monitoring consultant to design the blasting operations and provide a vibration monitoring program as specified in the Contract Drawings and Specifications.

    C. All survey monitoring shall be done by Registered Professional Surveyor licensed in the State of Tennessee 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 constructing activities or those of his subcontractors.

   1.07 DESCRIPTION OF INSTRUMENTATION SYSTEMS

    A. Convergence Measurement Tape Extensometer System (TE)

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

    2. Sets of convergence reference points will be installed as shown on plans.

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

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

    B. Inclinometer Casing (I)

    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.

    C. Multi-Position Borehole Extensometer (MPBX)

    1. An array of rods extending to various depths and grouted into place. Used to measure movement of the rock or soil at the anchor points relative to a fixed reference head.

    D. Ground Water Monitoring Devices

    1. Simple Standpipe Piezometer (PZ): an open standpipe with a well screen or filter at the lower end, sealed into a borehole. Used to measure groundwater level.

    2. Pneumatic Piezometer (PN): a pressure cell enclosed within a porous filter, with two tubes that extend to the surface. Provides a direct, accurate measurement of pore water pressure within soils.

    3. Ground Water Monitoring Well (MW): similar to simple standpipe piezometer, but large enough to develop and obtain water samples for water quality testing.

    E. Settlement Monuments (SM)

    1. A monument embedded in the soil or a point fixed on an existing permanent feature used to measure elevations. Allows measurement of surface movements to evaluate ground loss or slope movements during construction activities.

   1.08 VIBRATION MONITORING

    A. The Contractor's vibration monitoring consultant shall provide vibration monitoring services in accordance with the approved vibration monitoring plan at all locations where blasting is being performed. The Contractor's vibration monitoring plan shall identify potential locations for blast monitoring equipment. The Contractor's consultant shall setup, install, and operate equipment capable of detecting and recording ground vibrations and air-blast overpressure at selected locations while blasting operations are in progress. Such vibration monitoring equipment may be portable or permanently installed.

    B. The vibration monitoring plan shall require the Contractor to advise the neighboring property owners of the pending construction. Blasting and vibration monitoring operations shall be described to them.

   1.09 INSTRUMENT LOCATIONS

    A. Instrument locations shall be installed at the locations and to the depths indicated on the attached Instrumentation Schedule.

    B. All instruments shall be installed within one foot of the horizontal 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.

    C. 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 GENERAL

    A. This part shall include the furnishing of all materials of the dimensions and types as shown on the Drawings or as established by the Engineer.

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

   2.02 MATERIALS

    A. Tape Extensometer System:

    1. Convergence Reference Points: Stainless steel eyebolts with lock nuts rigid enough to resist bending under the tape tensioning loads. Provide No. 6 reinforcing steel, six inches long which is drilled and tapped for 1/4-20 thread and compatible with the eyebolts.

    2. Calibration Frame: Provide a rigid steel member ten (10) feet long with permanently attached anchors at each end. 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 51811500 manufactured by Slope Indicator Co., Seattle, WA, or approved equal.

    4. Provide protective covering for each convergence reference point to protect from damage due to construction operations and adverse environmental conditions.

    B. Inclinometer (See Figure 1 - Inclinometer Casing, attached):

    1. Casings and Couplings: Casings shall be made of semi-rigid ABS plastic, the non-telescoping type, and with 2.75-inch outside diameter. 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 55 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 longitudinal grooves space 90 degrees apart with a tolerance equal to or less than one degree in ten feet that are compatible with the inclinometer sensor. Telescoping couplings compatible with casing shall have a range of 6 inches in both tension and compression in soil. Non-telescoping couplings shall be used in rock. Casings and telescoping couplings, and non-telescoping couplings shall be Model Number 51111100, 51111200, and 51111400, respectively, manufactured by Slope Indicator Company, Seattle, WA, or approved equal. 

    2. Inclinometer Sensor: The sensor shall be waterproof and shall be compatible with the inclinometer casing. The sensor shall be capable of measuring the angle of inclination in two orthogonal directions. Provide Model Number 50325-E manufactured by Slope Indicator Company, Seattle, WA, or approved equal.

    3. Cable: Cable shall be a minimum of 65 feet in length, waterproof and compatible with sensor and readout unit. Provide Model Number 5060100 manufactured by Slope Indicator Company, Seattle, WA, or approved equal.

    4. Pulley Assembly: Pulley assembly shall be compatible with inclinometer sensor and casing and shall be sufficiently strong to lift inclinometer sensor. Provide Model Number 51104606 manufactured by Slope Indicator Company, Seattle, WA, or approved equal.

    5. Readout Unit: Readout Unit shall be compatible with the inclinometer sensor and shall provide a digital display in English units with automatic polarity signs. Provide Model Number 50368 manufactured by Slope Indicator Company, Seattle, WA, or approved equal.

    6. Protective Covering: Provide lockable protective covering to protect from traffic, construction activities, vandalism and adverse environmental conditions.

    7. Dummy Probe: Equal in dimension to the inclinometer sensor, but shall not contain any internal electronics and shall be compatible with the casing and coupling and be model 50304800 Slope Indicator Company or approved equal.

    8. Bottom Caps: ABS semi-rigid plastic to form a water tight seal.

    C. Multiple-Position Borehole Extensometer (See Figure 2 - Multi-Position Borehole Extensometer, attached):

    1. Untensioned mechanical rod-type; three anchors; a fixed reference head; an access box; removable mechanical readout; insensitive to traffic vibrations; sealed against intrusion of dirt, grout, and water; corrosion resisting; able to operate in water; able to operate correctly whether installed vertically or inclined; with a minimum service life of three years. MPBX shall be as manufactured by Slope Indicator Co., Seattle, WA, or approved equal, and shall have the following characteristics:

    a. Able to measure movements of the anchors relative to the reference head to a sensitivity of 0.001 inch over a range of two inches without resetting.

    b. Range extendable by resetting.

    c. Maximum variation of 0.005 inch from the mean of a repeated succession of readings (repeatability).

    d. Reference head permits easy cleaning of the measuring surfaces.

    e. Anchor assemblies fit into a drill hole having a maximum diameter of three inches and are grouted in place.

    f. Stainless steel rods encased in oil or grease filled plastic tubes with stainless steel tips for the exposed ends of the rods.

    g. Deformed or grooved anchors for secure anchorage with the grout.

    D. Readout Units for MPBX:

    1. Mechanical depth micrometer with a lock to hold the reading until release.

    2. Two readout units total, plus one standard gauge block for periodic checks of the accuracy of the readout units.

    3. Range 0-6 inches

    4. Stainless steel reference points.

    E. Surface Access Vault for MPBX (See Figure 3 - Instrument Surface Access Box, attached):

    1. Designed to accommodate the instrument and allow easy reading and maintenance of the instrument.

    2. The access vault shall be a PEMCO lockable vault model No. 104-242424, or equal. The PEMCO vault is available from:

    Drillers Equipment Supply, Inc.

    1015 Portwest Drive

    St. Charles, Mo. 63303

    3. The access lid shall be of medium duty iron casting in non-traffic areas and heavy duty if subjected to vehicle loading, equipped with a locking device to prevent unauthorized opening.

    4. Removable top for major work on the instrument.

    5. Six inch cast-in-place vault slab isolated from the instrument and provided with an adequate footing below base slab with a minimum of 6 inches of compacted backfill.

    6. Vault slab isolated from vault walls by a one-inch styrofoam board.

    7. Equipped with an adequate drain, placed as far from the reference head as possible, augured at as great an angle from vertical as possible, away from the direction the instrument hole is drilled and filled with pea gravel.

    F. Monitoring Wells and Standpipe Piezometers (See Figure 4 - Simple Standpipe Piezometer and Figure 5 - Monitoring Well, attached):

    1. Riser shall consist of Schedule 40 PVC, flush threaded, with O-ring seals, factory cleaned with protective wrapping for cleanliness, manufactured for this purpose.

    2. Monitoring well risers and screens shall be a minimum 2 inch inside diameter, and standpipe piezometer risers and screens shall be a minimum 1 inch inside diameter.

    3. Well screen shall consist of PVC with 0.01 inch slots, flush threaded, O-ring seals, factory cleaned with protective wrapping for cleanliness, manufactured for this purpose and fitted with a screw on end cap.

    4. Sand shall be clean silica sand and shall extend at least 2 feet above the top of the well screen.

    5. The sodium bentonite seal shall extend at least 2 feet above the sand and shall be hydrated with distilled water.

    6. The borehole diameter for well installation shall be not less than 3 times the well screen diameter. At least 6 inches of clean silica sand shall be placed at the bottom of the borehole beneath the end of the well screen.

    7. The annular space above the bentonite plug shall be grouted with cement-bentonite grout that contains 3% to 5% bentonite by weight and potable water.

    8. Manholes for monitoring wells shall be DSI Model 100C-8 "0 x 12", part no. 560 LMHC 8 DSI, or equal. Manholes are available from:

    Drillers Service, Inc.

    P.O. Drawer 1407

    Hickory, N.C. 28603

    (704) 322-1100

    9. The wells shall be flush mounted in manholes and fitted with locking caps. The manholes shall be embedded in concrete that extends at least 18 inches below ground surface and is sloped to drain water away from the well head.

    10. Provide two electronic water level indicators capable of measuring water level to the nearest 0.01 foot.

    11. Decontaminate all tools, riser, screen as needed in accordance with EPA guidelines.

    12. Develop the well until water is visibly clear by hand bailing or pumping.

    G. Pneumatic Piezometers (See Figure 6 - Pneumatic Piezometer, attached):

    1. Shall consist of Slope Indicator Company (Sinco), 1 inch piezometer, Model No. 51417802 with minimum of 100 feet of tubing or approved equal.

    2. Provide suitable, lockable terminal pipe or lockable terminal box to accommodate 6 pneumatic piezometers.

    3. Provide one pneumatic pressure indicator, Slope Indicator Company (Sinco) Model 211 with 0.1% gauge or approved equal.

    4. Grout and sand shall meet the requirements stated for monitoring wells.

    H. Settlement Monuments (See Figure 7 - Settlement Monument, attached):

    1. Shall consist of Grade 60, No. 4, 3 foot long reinforcing steel, embedded in 3000 psi concrete.

   PART 3 EXECUTION

   3.01 GENERAL

    A. This part shall include the placing of all specified instruments 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 local ordinances and sanitary codes, the regulations of the Department of Environment and Conservation, 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 measures as he deems necessary, subject to approval by the engineer, 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 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 if required.

   3.05 EXISTING WATER WELLS

    A. The Contractor shall locate and record water levels 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 the 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 15 days after receiving notice to proceed. Inclinometer casings shall be installed and baseline readings established at least 14 days prior to excavation. MPBX shall be installed at least 14 days prior to the advancement of the tunnel bore within 200 feet of the probe. Settlement monuments shall be installed at least 7 days prior to the open cuts or when tunnel excavations are within 200 feet of the settlement monuments.

    C. Method of Installation: Instrument installation shall be as recommended by the manufacturer and as detailed herein.

    1. Installation of Tape Extensometer Points:

    a. Drill three holes 10 inches deep at the crown and left and right spring lines at the locations indicated on the drawings following completion of tunnel excavation at each location.

    b. 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.

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

    2. Installation of Inclinometer Casing:

    a. The inclinometer casing shall be installed at the locations indicated on the Contract Drawings to depths of 5.0 feet below the bedrock soil interface.

    b. Use a borehole size recommended by the instrument manufacturer. Case the hole through overburden into rock using casing if required to prevent caving, and remove the casing after installation and grouting of the inclinometer casing.

    c. The rock formation shall be cored continuously from the top of the 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.

    d. The inclinometer casing shall be installed so that the pairs of grooves in the casing are aligned approximately parallel and perpendicular to the sewer alignment and to nearby structures that could be affected by ground movements.

    e. The casing shall be installed as vertically as possible and shall not be inclined more than 2 degrees from vertical.

    f. 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. Drilling and Installation of MPBX:

    a. Install MPBX as detailed herein and according to the manufacturer's recommended installation procedure.

    b. Use a minimum 3 inch diameter borehole for the MPBX. The use of drilling mud, oil, or other materials that would adversely affect the bond between rock, grout, and extensometer anchors shall not be permitted in the hole. Case the hole through overburden into rock, using minimum four inch PVC pipe. PVC pipe casing shall be left in place as recommended by the instrument manufacturer. 

    c. Advance the hole in rock by rotary drilling methods and recover 2-1/8 inch diameter (NX size) rock cores using a series M double tube core barrel. Drill in conformance to the applicable portions of ASTM D-2113. Place core in 5 foot long wooded boxes and deliver to a storage site approved by the Engineer.

    d. Drill MPBXs vertically or at a incline from the location shown to intersect the opening. Extend the holes to within 2 feet elevation above the estimated crown of the tunnel excavation at the point of intersection.

    e. Grout the extensometer anchors, attached rods, and protective tubing within the borehole. Use an approved grout mix. Grout from the bottom of the borehole until the borehole is filled. Do not interrupt grouting until the installation is complete. Ensure intimate rock-grout contact.

    f. Terminate the top of the extensometer rods and protective tubing within the extensometer head.

    g. Clearly identify on the extensometer head, the instrument identification number for each extensometer anchor and connecting rod.

    h. Install the extensometer access box and cover on the MPBX. Backfill around the box with suitable material and patch the surrounding area to match the existing conditions.

    4. Installation of standpipe piezometers:

    a. PZs shall be installed at the locations and to the depths indicated on the Instrument Schedule and the Contract Drawings.

    b. Advance the hole in rock by rotary drilling methods and recover 2-1/8 inch diameter (NX size) rock cores using a series M double tube core barrel. Drill in conformance to the applicable portions of ASTM D-2113. Place core in 5 foot long wooded boxes and deliver to a storage site approved by the Engineer.

    c. Use a minimum borehole size of 3 inches. Case the hole through the overburden soil and into rock as necessary to prevent caving.

    d. The riser shall be installed as vertically as possible and shall not be inclined more than 2 degrees from vertical.

    e. Remove the casing after installation and place screen, riser, sand, bentonite plug, and concrete as required.

    f. Clearly identify on the piezometer access box the instrument identification number.

    g. Install the piezometer access box and cover on the PZ. Backfill around the box with suitable material and patch the surrounding area to match the existing conditions.

    5. Installation of monitoring wells:

    a. Monitoring wells shall be installed using EPA standard methods as outlined in the RCRA Technical Enforcement Guidance Document.

    b. MWs shall be installed at the locations and to the depths indicated on the Instrument Schedule and the Contract Drawings.

    c. Advance the hole in rock by rotary drilling methods and recover 2-1/8 inch diameter (NX size) rock cores using a series M double tube core barrel. Drill in conformance to the applicable portions of ASTM D-2113. Place core in 5 foot long wooded boxes and deliver to a storage site approved by the Engineer.

    d. Use a minimum borehole size 3 times the diameter of the riser (2 inch riser requires 6 inch diameter borehole). Case the hole through the overburden soil and into rock as necessary to prevent caving.

    e. The riser and screen shall be installed as vertically as possible and shall not be inclined more than 2 degrees from vertical.

    f. Remove the casing after installation and place screen, riser, sand, bentonite plug, and concrete as required.

    g. Clearly identify on the monitoring well access box the instrument identification number.

    h. Install the monitoring well access box and cover on the MW. Backfill around the box with suitable material and patch the surrounding area to match the existing conditions.

    6. Installation of pneumatic piezometers:

    a. PNs shall be installed at the locations and to the depths indicated on the Instrument Schedule and the Contract Drawings.

    b. Use a minimum borehole size of 3 inches. Case the hole through the overburden soil to rock as necessary to prevent caving.

    c. Protect the double pneumatic tubing with PVC casing or similar material.

    d. Place the pneumatic transducer and sand pack as required.

    e. Clearly identify on the PN terminal box the instrument identification number.

    f. Install the PN terminal box as recommended by the manufacturer. Backfill around the box with suitable material and patch the surrounding area to match the existing conditions.

    7. Installation of Settlement Monuments:

    a. Settlement monuments shall be installed at the locations indicated on the Instrument Schedule and the Contract Drawings.

    b. If necessary the locations can be adjusted to avoid conflict with obstructions.

   3.07 INSTALLATION TOLERANCES

    A. Establish the initial elevation of the instruments and settlement monuments to 0.005 feet.

    B. 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.

    C. Establish survey turning points so that backsite and foresight distances 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 5 days of notification.

    C. All terminal boxes and covers shall be lockable and keyed alike. Provide 3 sets of keys to the Engineer.

    D. 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 2 feet of inclinometer casings, MPBXs, PZs, PNs, MWs, SMs, and the protective covers; plug remaining open portions, if any, with concrete. Backfill casings with grout, full depth, filling from the bottom to the top.

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

    C. Remove reference points and paint marks on buildings and patch any holes on walls resulting from reference point removal.

   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 and subject to approval of the Engineer and the Contractor's insurance carrier, 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.

    B. The Contractor will perform a pre-blasting assessment of all structures within 500 feet of any area where blasting will be performed. Pre-blast inspections shall be made by qualified specialist retained by the Contractor and subject to approval of the Engineer and the Contractor's insurance carrier, 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.

    C. The assessments shall include a reconnaissance of the structures located entirely or partially within the above specified distances.

    1. The assessments shall include identification and documentation of all visible structural and cosmetic defects with written descriptions, videography, photographs, diagrams and measurements, including the location, length, spacing and separation width of all visible cracks (hairline width or greater).

    2. The assessment shall also establish water levels of existing water wells within 500 feet of the tunnel operations or shaft excavations.

    3. Structures having no exterior cracks or other damage shall be photographed on the exterior only. The preconstruction or pre-blast inspections for structures showing exterior cracks or other damage shall produce diagrams of all walls, partitions, floors and ceilings showing existing cracks, descriptions of interior basement or foundation cracks, elevations, photographs of exterior cracks or damage, and such other data as is applicable to locate and define the amount and extent of existing damage.

    4. The Contractor shall prepare and deliver to the Engineer two (2) bound copies of the preconstruction and pre-blast inspections containing all field notes taken, sketches and diagrams prepared, photographs and video-tapes obtained, descriptions and reports, all signed and witnessed by those taking part in the inspection.

    5. Thereafter, as construction progresses, the Contractor shall reinspect as often as is necessary, or as requested by the Engineer, to verify the adequacy of his construction methods for prevention of damage and to obtain sufficient evidence for use in defense against possible claims for damage from third parties. Data obtained by the Contractor from each reinspection shall be promptly delivered to the Engineer.

    6. Inspection reports shall be submitted to the Engineer before any shaft, tunnel or sewer excavations proceeds closer than 500 feet to areas scheduled for inspection per the criteria contained herein.

    D. 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.

    E. In the event that any property owner denies access for the survey of structures and facilities within the specified limits, the Contractor shall notify such property owner, by certified mail, of the intent of the survey. If after two (2) weeks access is still denied, the Contractor shall notify the property owner once again by certified mail, stating that this is the final notification. Submit copies of all correspondences between the Contractor and the Property owner(s) to the Engineer. The Engineer, upon review of the submitted correspondences, may waive requirements set forth in Article 4.01.A. of this section of the specifications. However, the Contractor is fully responsible for claims and damage arising from his construction operation.

    F. A post construction assessment shall be made by the Contractor to document and note changes in the conditions of the structures surveyed prior to construction. One copy of this document shall be provided to the Engineer.

   PART 5 CONSTRUCTION MONITORING

   5.01 INITIALIZATION OF INSTRUMENTS

    A. The initial elevations of all instrument and settlement monuments shall be established in accordance with the following schedule unless otherwise directed by the Engineer.

    1. Twenty-four (24) hours after installation. Instruments will be approved and considered initialized after two consecutive readings within ± 0.01 feet of each other are obtained at each location. Instruments must be properly initialized and approved by Engineer.

   5.02 FREQUENCY OF INSTRUMENT MONITORING

    A. Tape extensometer points shall be read daily for one week following installation and then once weekly until the final liner is installed.

    B. Multi-position borehole extensometers shall be read on the following schedule:

    1. Daily, while tunnel excavating and construction activity is taking place within 200 feet up and down station of the monitoring point. Twice daily, while the excavation face is within 50 feet of the instrument. Weekly monitoring shall be continued until the final liner is in place.

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

    3. If total cumulative movement in excess of one-eighth (0.125) inch occurs, the Engineer will be notified immediately and the MPBX shall be monitored twice daily until directed otherwise by the Engineer.

    C. Inclinometer, piezometers, pneumatic piezometers, and monitoring wells shall be monitored on the following schedule after initialization:

    1. Twice daily, while construction activity is within 75 feet of baseline station.

    2. Daily while construction activity is within 75 to 200 feet of baseline station.

    3. Once Weekly until construction activity is complete.

    D. Settlement monuments shall be read daily if construction activity is within 100 feet of the baseline station and once per month if construction activity is more than 100 feet away.

    E. Vibration measurements and air overpressure readings shall be taken for all blasting operations, in accordance with the Contractor's approved blasting and vibration monitoring plan.

   5.03 REPORTS

    A. Readings shall be recorded according to the schedule listed in Paragraph 5.02. The Contractor shall review the readings upon receipt. Anomalous readings shall be immediately reported to the Owner and Engineer and transmitted in writing within twenty four (24) hours. All instrument readings, summaries, and graphs shall be transmitted in writing to the Owner and the Engineer as described in 1.03 H.2. at least once weekly.

    B. Anomalous reading could include significant changes from previous readings, trends toward dangerous water levels or magnitudes of deflection, and unexpected directions of deflection. Total cumulative differential movements for Is, TEs, MPBXs, or SMs at any location in excess of one-quarter (0.25) inch (one-quarter inch differential from initialized reading) shall be reported to the Engineer immediately (same workday). Cumulative movements in excess of one-quarter (0.25) inch shall require additional survey monitoring to verify adequacy of the contractor's operations. Total cumulative differential elevation change of water levels for PZs, PNs, or MWs at any location in excess of 1 foot (1 foot differential from initialized reading) shall be reported to the Engineer immediately (same workday).