Section 02400 GEOTECHNICAL INSTRUMENTATION AND MONITORING

Section 02400

GEOTECHNICAL INSTRUMENTATION AND MONITORING

PART 1 - GENERAL

1.1 THE REQUIREMENT

A. This section only covers furnishing, installing, and monitoring geotechnical instrumentation for the tunnel 17 structure, 72” trickling effluent pipeline and between digesters 10 and 13 (tunnel 29) structures as indicated herein in addition to the points required for monitoring the protection system (shoring).

1.2 DEFINITIONS

A. Displacement Reference Point (DRP): Established point on the ground surface monitored by optical survey methods to determine vertical displacements, if any, occurring during construction.

B. Lateral Displacement Reference Point (LDRP): Established point on top of the shoring, and monitored by optical survey methods to determine horizontal displacements, if any occurs during construction.

C. Structure Movement Monitoring Point (SMMP): Established point on the structure wall and monitored by optical survey methods to determine vertical and horizontal displacements occurring during construction.

D. Inclinometer: Special casing installed and grouted within vertical borings in the in situ soil materials. A probe, lowered within the casing, is used to monitor any horizontal displacements occurring during construction relative to a fixed reference point at the top and bottom.

1.3 RELATED WORK SPECIFIED ELSEWHERE

A. The requirements of the following sections and divisions apply to the Work of this section. Other sections and divisions of the Specifications, not referenced below, shall also apply to the extent required for proper performance of this Work.

1. Section 02164, Tieback Anchors

2. Section 02361, Steel Sheet Piling

3. Section 02200, Earthwork

4. Section 02624, Existing Utilities

All Work specified herein shall conform to or exceed the applicable requirements of the referenced portions of the following publications to the extent that the provisions thereof are not in conflict with other provisions of these Specifications.

Comply with the applicable editions of the following codes, regulations, and standards. National Bureau of Standards

1.4 CONTRACTOR SUBMITTALS

A. Submittals shall be made in accordance with the General Requirements, Additional

General Requirements, and as specified herein.

B. Working Drawings:

1. Submit working drawings showing the proposed location, tip elevation, and surface elevation of any geotechnical monitoring devices proposed by the CONTRACTOR and accepted by the ENGINEER as required hereafter.

2. Proposed schedule and procedures for installation of inclinometer, LDRPs, DRPs, and SMMPs.

3. The proposed drilling equipment and techniques for installation of inclinometers.

4. Schedule for initial surveys.

5. Details of proposed protective housing over inclinometer casings.

6. After instrumentation installation is completed, submit as-built drawings. The information shown on these as-built drawings shall include:

a. Instrument identification numbers and locations, with initial elevations, and coordinates, as applicable for each instrument.

b. Information obtained during installation procedures, including drilling logs.

c. As-built installation details of each instrument, including depths, lengths, elevations, materials used, and dimensions of key elements.

C. Product Data:

1. Manufacturers' applicable literature for instrumentation and testing equipment, including:

a. Operating manuals and technical specifications. b. Range and accuracy of measurements.

c. Installation instructions. D. Quality Control Submittals:

1. Qualifications and experience of the personnel to install the instrumentation.

2. Qualifications and experience of personnel performing the monitoring and data reduction.

3. Calibration certificates for equipment supplied.

4. Quality control inspection checklist certificates.

1.5 SEQUENCING AND SCHEDULING

A. Do not perform any excavation below grade level until all instrumentation as shown on the accepted submittal shop drawings has been installed.

B. Unless noted otherwise on the drawings, Inclinometers shall be installed before installation of shoring within 100 feet of inclinometer.

C. Inclinometers shall be removed after the sheet piles installation in the areas next to tunnel 17 and the trickling filter effluent pipe. . Inclinometers in the digesters area shall remain until the construction of tunnel 29 is complete.

1.6 QUALITY ASSURANCE

A. Installation shall be performed in the presence of the ENGINEER. Manufacturer's supervision shall be provided for as many installations as necessary to train the CONTRACTOR’s personnel to install these devices properly without such supervision.

B. Contractor Qualifications:

1. Installation and monitoring of survey points (including DRPs, LDRPs, and

SMMPs shall be performed by a Land Surveyor licensed in the State of California.

2. Installation of instruments shall be performed by qualified technicians with at least 2 years experience in geotechnical instrument installation within the last 5 years.

PART 2 - PRODUCTS

2.1 MATERIALS

A. Any of the following methods may be used to establish DRPs and LDRPs:

1. The DRPs shall consist of a reinforcing bar installed in the existing soil adjacent to the pipeline. The locations of the DRPs and their construction shall be indicated on the submittal drawings.

2. The LDRPs shall consist of a survey prism welded or connected to the shoring. B. SMMPs shall consist of a scribed brass disc attached to the top of the wall.

2.2 EQUIPMENT

A. Inclinometer Casings

1. ABS semi-rigid plastic with an outside diameter of 2.75 inches with snap together couplings and with sufficient flexibility to accurately reflect horizontal ground movement.

2. The casings shall have four internal longitudinal grooves equally spaced, at 90 degrees.

3. Casings shall be Slope Indicator Company Model 51150210 with accessories, Or

Equal, from itmsoil.

4. Bottom caps shall be of ABS semi-rigid plastic to form a watertight seal. B. Inclinometer Probe

1. The inclinometer probe shall provide measurements in English Units and be a

Durham Geo Slope Indicator Model 50302500, Or Equal from itmsoil.

2. The control cable supplied with the inclinometer probe shall be as manufactured by Durham Geo Slope Indicator, Or Equal.

C. Readout Device

1. The readout device for the inclinometer probe shall be Durham Geo Slope

Indicator Digitilt Datamate Readout, Model No. 50310900, Or Equal, from itmsoil.

2.3 MIXES

A. Cement grout for inclinometer casings shall be as recommended by the manufacturer.

2.4 SOURCE QUALITY CONTROL

A. A final quality assurance inspection and calibration shall be made of each instrument prior to shipment. During the inspection, a check list shall be completed to indicate each inspection and test detail.

B. The manufacturer shall provide certification that products, materials and equipment meet the specified requirements. A completed copy of the check list shall be supplied with each instrument. Certification shall be provided to indicate that the manufacturer's test equipment is calibrated to meet the standards established by the National Bureau of Standards.

PART 3 - EXECUTION

3.1 GENERAL

A. The instrumentation program and the data derived shall not relieve the CONTRACTOR of its responsibility to protect adjacent structures and facilities, and to provide an adequate sheet pile tieback support system.

B. All instrumentation hardware, protective covers, read-out equipment, and equipment and material necessary to conduct the monitoring program shall be provided by the CONTRACTOR. Prior to installation, all materials and equipment shall be available for inspection by the ENGINEER.

C. Except where otherwise specified, the CONTRACTOR shall maintain or construct access to all monitoring points, instruments and monitoring facilities to ensure as a minimum that instruments can be monitored at the frequencies specified herein.

D. Responsibility

1. The CONTRACTOR shall be fully responsible for the furnishing, installation, testing, calibration, and maintenance of all instrumentation, unless specified otherwise.

2. The CONTRACTOR shall retain a qualified geotechnical firm to monitor all DRPs, LDRPs, MMPs and inclinometers, interpret data, and furnish the ENGINEER with a copy of the results.

E. Additional instrumentation shall be installed as directed by the ENGINEER for an event that may require supplemental instrumentation and monitoring.

3.2 PREPARATION

A. Prior to construction, the CONTRACTOR shall establish survey bench marks and baselines necessary to monitor displacement reference points, lateral displacement reference points, and pipeline movement monitoring points to the tolerances stated herein.

B. Benchmarks shall be located outside the zone of influence of all excavations.

3.3 DISPLACEMENT REFERENCE POINTS AND LATERAL DISPLACEMENT REFERENCE POINTS

A. Install DRPs, LDRPs, and SMMPs at the locations indicated on the proposed working drawings prepared by the CONTRACTOR and accepted by the ENGINEER..

B. Survey position and elevation of these points to the tolerances specified herein prior to performing any excavation at the site.

C. Periodically monitor position and elevation of these points as follows:

1. Monitor continuously all installed and identified reference points during installation of protection system for all locations.

2. Monitor weekly, thereafter, after the excavation is complete and construction has been initiated on tunnel 29 and the points on the protection system. Monitoring on a daily basis if, in the opinion of the ENGINEER, excessive movements are taking place.

3. Survey data taken by the CONTRACTOR shall be made available to the

ENGINEER within 1 hour after the readings are taken.

4. The ENGINEER reserves the right to modify the monitoring schedule.

D. Records the survey and inclinometer monitoring data and make such interpretations available to the ENGINEER within 1 hour. Survey and inclinometer monitoring data shall be submitted in a graphical format that indicates movement relative to time and elevation of excavation.

E. Survey Tolerances:

1. Establish initial elevation and position of each DRP to 0.01 foot.

2. Establish the initial position of each LDRP to 0.01 foot.

3. Record subsequent elevation and position of each DRP to 0.01 foot.

4. Record subsequent position of each LDRP to 0.01 foot.

5. Establish initial elevation and position of each SMMP to 0.01 foot.

6. Establish subsequent elevation and position of each SMMP to 0.01 foot.

7. If, in the opinion of the ENGINEER, excessive movement is taking place relative to the limiting displacement criteria specified in the table below, the CONTRACTOR shall provide supplemental support and modify construction procedures, as necessary, to minimize additional ground displacement as accepted by the ENGINEER. If the movement of the structure reaches the limiting displacement criteria listed in the table below, the CONTRACTOR shall stop excavation, and not resume work until the ENGINEER has determined the required remedial measures.

Monitoring Point

Designation Limiting Displacement Criteria

DRP 0.10 percent of supported excavation depth

LDRP 0.10 percent of supported excavation depth

MMP Resultant of vertical and horizontal displacement not to exceed 0.5 inch between two adjacent pipe joints (typical pipe joint spacing is 20 feet) or the as a change in building elevation from initial reading

Supported excavation depth is defined as the difference between ground surface behind the shoring and the ground surface in front of the shoring when the reading of the monitoring device was recorded.

3.4 INCLINOMETERS A. Installation

1. Install inclinometers at the locations shown on the submittal drawings or at locations accepted by the ENGINEER. Survey the position and elevation of the top of the casing to the tolerances specified herein immediately following installation. The position and elevation of the top of the existing casing shown on the drawings shall also be surveyed.

2. Install inclinometer casing in a minimum 5-inch diameter, vertical borehole extended at least 20 feet below the base of the excavation at the face of the shoring and at least 15 feet into medium dense to dense sand or firm to stiff native soils. A continuous inclinometer boring log of observations shall be made concerning subsurface conditions encountered during drilling. The boring shall be advanced and cleaned by rotary wash boring methods. Stabilize borehole with temporary casing or drilling mud as required. Remove temporary casing during installation of the inclinometer casing.

3. A protective cap shall be placed on the bottom of inclinometer casing so that a waterproof seal is formed.

4. Additional sections of inclinometer casing shall be installed using appropriate couplings and lowered down the hole. Telescoping couplings, if used, shall be fully extended. All couplings shall provide a watertight seal to casing sections.

5. Add clear water to the inside of inclinometer casing to facilitate lowering the inclinometer casing through water or drilling mud in the borehole.

6. Orient casing so that the orthogonal grooves are positioned parallel and perpendicular to the excavation wall.

7. Grout annulus between inclinometer casing and borehole with ENGINEER accepted grout mix per manufacturer's recommendations, Place grout using a detachable, flexible tremie pipe or grout pipe attached to the bottom of the inclinometer casing, ensuring an intimate ground/grout contact.

8. Immediately after grouting, jet and flush the inclinometer casing with clear water.

9. Establish survey reference point by scribing a mark in the top edge of casing.

10. Install approved protective housing. B. Frequency of Monitoring

1. The CONTRACTOR shall monitor inclinometers daily during excavation and shoring installation and weekly thereafter until the excavation has been backfilled.

2. The ENGINEER reserves the right to modify the monitoring schedule. C. Survey Tolerances

1. Establish initial elevation and position of the top each inclinometer casing to 0.01 foot.

2. Record subsequent elevation and position of top of each casing to 0.01 foot.

3. Install inclinometer casings within two percent of vertical for the entire length.

D. The CONTRACTOR shall also scribe the top of each inclinometer casing and use it as a DRP.

3.5 PROTECTION AND REPLACEMENT

A. Take every practical measure to prevent damage to the instruments and ancillary equipment during handling, installation and construction operations. Maintain all the instruments required for long term monitoring in a satisfactory working order.

B. All damage resulting from construction operations, weather, traffic, or vandalism shall be repaired or replaced and installed at no additional cost to OCSD within 48 hours.

C. Instrumentation or supporting hardware found to be malfunctioning at any time shall be replaced within 48 hours at no additional cost to OCSD.

D. The top of the inclinometer installations shall be enclosed within approved protective housing units. The top of the protective housing unit for the inclinometer installations shall protrude no more than 24 inches above the existing ground surface.