SPECIAL PROVISION Excavation

Transcription

1 SPECIAL PROVISION Excavation For this project, Item 110, Excavation, of the Standard Specifications, is hereby amended with respect to the clauses cited below, and no other clauses or requirements of this Item are waived or changed hereby. This special provision covers the following items of work: Rock blasting for construction of the North Main Street Bridge in Fort Worth, TX. Article Construction is supplemented by the following: D. Blasting The Contractor shall comply with the applicable rules, regulations and standards established by the Regulatory Agencies, codes and professional societies listed herein, including rules and regulations for storage, transportation, handling, and use of explosives. These rules and standards include but are not limited to the following: a. The Federal Occupational Safety and Health Act of 1970 and the Construction Safety Act of 1969, as amended. b. Safe Explosives Act, Title XI, Subtitle C of Public Law , Interim Final Rule. c. OSHA of 1970, 29 U.S.C., Section 651 et seq., including safety and health regulations for construction. d. CFR 27, U.S. Department of Justice, Alcohol, Tobacco, Firearms and Explosives Division (ATF). 27 CFR Part 555, Implementation of the Safe Explosives Act, Title XI, Subtitle C of Public Law ; Interim Final Rule. e. Organized Crime Control Act of 1970, Title XI, Public Law , approved October 15, 1970, as amended. f. CFR 49, Parts (DOT RSPA); (DOT FHA). g. City of Fort Worth, Fire Department Explosive Permit Rules; (817) h. Non-regulating Industry Support Organizations Definitions 1. Vibration Subcommittee of the International Society of Explosive Engineers (ISEE), blast monitoring equipment operation standards (1999). 2. IME (Institute of Makers of Explosives) Safety Library Publications (SLPs). a. Blaster-in-Charge: The single designated and licensed person with complete responsibility and total authority over all decisions involving safe handling, use and on-site security of explosives. c. Blasting Consultant: A person with specialized experience and academic knowledge of commercial explosives, controlled blasting applications, vibration and air-overpressure

2 control; and uses this knowledge to evaluate, plan, and oversee the safe use of explosives in commercial applications in accordance with blasting industry and regulatory standards. d. Charge-per-Delay: For vibration control, any charges firing within any 8-millisecond time period are considered to have a cumulative effect on vibration and air-overpressure effects. Therefore, the charge-per-delay (W) is the sum of the weight of all charges firing within any 8-millisecond time period. For example, if two 100-lb. charges fire at 100 ms and one 115-lb charge fires at 105 ms, the charge per delay would be 315 lbs. e. Controlled Blasting: Excavation of rock using explosives, wherein the blast is carefully designed and controlled to provide a distribution of charge that will excavate the rock to the required limits but minimize overbreak, stressing, and fracturing of rock beyond the design lines. Controlled blasting techniques are generally limited to the perimeter of the excavation. Cushion blasting, smoothwall blasting, presplitting, and light blasting combined with line drilling are examples of controlled blasting techniques. Controlled blasting is required in all structure excavations. f. Cushion or Trim Blasting: A blasting technique in which the line of holes along the boundary of the excavation is detonated during the last delay period of the blast. The main burden is moved from the face by the main production holes leaving only a small burden to be removed by the line holes on the perimeter. Charges in holes along the final perimeter are lighter than charges used for holes in the mass blasting area. g. Decking: Separating the charge in a single hole into two or more portions separated by stemming, air gap, or void. h. Line Drilling: A method of overbreak control in which a series of very closely spaced holes is drilled at the perimeter of the excavation. These holes are not loaded with explosives. i. Occupied Building: Structure on or off construction limits that is occupied by humans or livestock. j. Peak Particle Velocity (PPV): The maximum of the three ground vibration velocities measured in the vertical, longitudinal and transverse directions. PPV measurement units are expressed in inches per second (in/s). k. Perimeter Holes: The blast holes drilled along the final limit of the excavation. l. Presplitting: A drilling and blasting technique wherein small diameter holes are drilled on close spacing along the neat excavation lines. The charges are small in diameter, specially prepared for presplitting, and are detonated ahead of the main production charges. This technique requires free relief of the perimeter and may require advance excavation of the production area to provide that relief. m. Primary Initiation: The method whereby the blaster initiates the blast(s) from a remote and safe location. Primary initiation systems use non-electric shock-tubes to convey firing energy from the point of initiation to blast locations. n. Production Holes: Blast holes in the main body of the rock mass being removed by drilling and blasting

3 o. Prohibited Persons: Persons prohibited from handling or possessing explosive materials as defined by the seven categories described in Section of 27 CFR (ATF Rules). p. Residential Building: Includes single and family dwellings, hotels, motels and any other structure containing sleeping quarters. q. Scaled Distance: A calculated value describing relative vibration energy based on distance and charge-per-delay. For ground vibration control and prediction purposes, Scaled Distance (Ds) is obtained by dividing the distance of concern (D) by the square root of the charge-per-delay (W), Ds = D/W 0.5 or W = (D/Ds) 2. Minimum scaled distance limits are used to establish charge weights and the units of scaled distance (Ds) are ft-lb For example, if a blast is designed to meet a minimum scaled distance of 60, the maximum charge-per-delay for a blast located 1000 feet from the structure of concern would be pounds [(1000/60) 2 ]. r. Smoothwall Blasting: A drilling and blasting technique using reduced hole-spacing similar to presplitting, except that the reduced charges in holes at the perimeter of the blast are detonated with adjacent mass-blast holes using the highest delay times. This technique requires free relief of the perimeter and may require advance excavation of the production area to provide that relief. s. Stemming: Crushed stone, tamped clay or other inert earth material placed in the unloaded collar area of blastholes for the purpose of confining explosive charges and limiting rock movement and air-overpressure (noise). Drill cuttings generated from potential NOA containing materials shall not be used as stemming. t. Subdrilling: The portion of the blasthole that is drilled below or beyond the desired excavation depth or limit. Subdrilling is generally required to prevent the occurrence of high or tight areas of rock between blastholes. Submittals a. General Blasting Plan, which shall include the following: 1. Explosives Transportation, Handling, and Storage Plan: at least 20 days before any explosives are brought to the site submit a plan describing proposed methods for transportation, handling, storage, and use of explosives. This plan shall include: a. A scaled map showing locations where explosives will be kept in temporary day boxes or delivery vehicles while on site. b. Include a copy of delivery records and other inventory report forms that will be used to document quantities of explosives and detonators delivered, used and removed from the site on days blasting work occurs. c. Indicate how explosives will be inventoried, secured and guarded to prevent theft or unauthorized use of explosives. 2. Describe general drilling and blasting methods including narrative regarding drilling equipment including model numbers, hole size, explosives, detonators, type and amount of stemming, method of primary initiation, and technical specifications (size and weight) of blast mats used to cover blasts

4 3. Manufacturer's data on material and equipment including type of explosive, cartridge size, detonator, seismographs, lightening detectors, blast initiation devices, plus other equipment required to perform the blast. 4. Include narrative and sample calculations that define how charge-weight-per-delay will be limited based on distance to structures of concern. 5. Include sample copies of the vibration/air-overpressure monitoring reports that will be submitted as required for this work. 6. Submit certificates of calibration for all monitoring equipment including recorders, sensors and microphones. b. A signed letter from the Contractor s blasting consultant confirming they have reviewed and approved the General Blast Plan. c. A resume and three references for projects completed in the last five years by the Blasterin-Charge in direct charge of the blasting operations shall be submitted to the TxDOT Representative with the Contractor s general blasting plan. d. Submit the resume of the independent Blasting Consultant with experience conforming to requirements of Part 1.05.B. e. Obtain two complete printed copies of all applicable codes, regulations, ordinances and monitoring standards, keep a copy in the project files at all times, and provide TxDOT Representative or his/her designated representative with a complete set of all applicable regulations. The Contractor s Safety Representative shall ensure that ongoing blasting work complies with all applicable regulations. f. Blasting Safety Plan for Use of Explosives: The Blasting Safety Plan shall include: 1. An acknowledgement that blasting-safety-related issues are the full responsibility of the Contractor. 2. A complete list of all authorities having jurisdiction over blasting operations involving the transportation, storage, handling and use of explosives. 3. A complete description of the clearing and guarding procedures that will be employed to ensure personnel, staff, visitors, and all other persons are at safe locations during blasting. This information shall include details regarding visible warning signs or flags, audible warning signals, method of determining blast area zones, access blocking methods, guard placement and guard release procedures, primary initiation method, and the system by which the Blaster-in-Charge will communicate with site security guards. 4. Include Material Safety Data Sheets (MSDS) and specific details about hazard communication programs for employees. 5. Describe equipment and procedures that will be used to monitor the approach of lightning storms and in the event of such, evacuation and site safety security plans. 6. Contingency plans for handling of misfires caused by cut-offs or other causes

5 7. Fire prevention plan details, including smoking policies, procedures and limitations for work involving any open flames or sparks, description and location of all firefighting equipment, and fire fighting and evacuation plans. 8. Description of the personal protective equipment that will be used by the Contractor's personnel, including but not limited to, safety glasses, hard-toe footwear, hard hats and gloves. g. Permits, Licenses and qualifications: Submit the following 20 days before any rock drilling or blasting work occurs on the site: 1. The qualifications and all licenses of proposed Blasting Supervisor or Supervisors and the Blaster in Charge, including prior experience with similar projects, shall also be submitted. 2. Valid blasting/explosives-use permit issued by City of Fort Worth Fire Department. 3. Copy of current Contractor s federal ATF blasting license. h. Submit two copies of Pre-Blast Survey Reports to the TxDOT Representative. These reports shall include the following: 1. A typewritten summary report naming the person who performed the survey and comments about structures and their existing condition. 2. Printed color 35-mm or 5-megapixel digital photographs documenting the preexisting condition of all structures and improvements located within 500 feet of excavation and rock blasting areas. i. Detailed Blasting Plans: For all individual blasts submit the information listed below. The review of a blasting plan by the TxDOT Representative shall not relieve the Contractor of responsibility to obtain adequate rock breakage, and to limit breakage to within the design excavation final lines and grades, and to ensure that flyrock does not result from the blasting operation. 1. A scaled drawing showing the location, orientation, number, diameter, and depth of blast holes relative to the specified stations, slopes, lines, and grades. 2. Calculations showing determinations of maximum charge-per-delay. 3. A detailed log showing the amounts of all explosives by type and stemming used in all charged holes, rock volume calculations, and powder factor calculations. 4. Drawing showing surface initiation and in-hole firing times of all charges. 5. Proposed date and time of blast. 6. A description of provisions that will be used to ensure no rock or other debris is moved on further than 10 feet from the immediate blast area. 7. Methods to prevent over-blasting and loosening of rock not indicated to be removed or disturbed. 8. Location of seismographs and instruments that will measure ground vibration and blast noise in Linear-decibel scale (2-Hz-response microphones)

6 9. Provisions for scaling after each blast, including when scaling will begin, and who will perform the scaling ensure blasted rock surfaces are stable before other work resumes. j. Blast Reports: These records shall be submitted along with seismograph and noise (airoverpressure) monitoring records. The blast reports shall include the following information: 1. Date, time, and location of each blast on scaled plan drawings and vertical sections. 2. Type of rock blasted, and round length, including amount of sub drilling if any. 3. Reference to approved Blasting Plan submittal noting any modifications. 4. Type, quantity, and weight of explosives, powder factor, total number and type of delays used, number of holes for each delay period, maximum charge per delay, stemming used and type of detonators. 5. Name and signature of the Blaster-in-Charge and Blaster s License number. 6. An evaluation of blast results indicating breakage, perimeter control results, depth of break and planned adjustments to the blast design for the next blast. 7. Comments regarding misfires and unusual results or effects. 8. Copies of blast vibration monitoring and noise (air-overpressure) measurement data and reports. Quality Assurance a. All work shall comply with the rules and regulations of Federal and State agencies having jurisdiction. Nothing contained herein shall be construed as permitting work that is contrary to such rules, regulations, and codes. b. Blasting Consultant 1. The Contractor shall retain an independent Blasting Consultant with at least 10 years experience involving controlled blasting work. The Blasting Consultant shall have directly participated in at least three projects of similar scope and complexity. The Blasting Consultant shall directly oversee all test blasts (first blasts) and actively participate in the development of preliminary blasting plans and blast design modifications, based on observed results and measurements. All blasting plans, test blasting plans and revisions shall be reviewed by and covered with a signed letter prepared by the Blasting Consultant. The Blasting Consultant will not be required to sign the individual Blast Plans provided they are signed by the onsite Blaster-in-Charge. 2. The Blasting Consultant shall not be an employee of the Contractor or any affiliated companies or suppliers of products to the project; and the Blasting Consultant must not have any conflict-of-interest affiliations with TxDOT, TxDOT Representative, or other entities involved with the work. 3. The Blasting Consultant shall be onsite when initial test blasts are done and as requested by TxDOT or their designated representative; the Blasting Consultant shall attend onsite meetings or open-house community meetings as requested by the

7 TxDOT Representative. The Blasting Consultant shall make at least two 1-day visits to the site. c. Blasting Personnel Qualifications: 1. The Contractor shall employ experienced, competent supervisors for blasting operations. These persons shall possess the required federal, state, and local licenses and permits. 2. The Blaster-in-Charge shall have a minimum of 5 years of experience and shall be able to document the completion of a minimum of three projects of similar scope and complexity, each including controlled blasting. Explosive Delivery, Storage, Handling and Security a. Explosives shall be handled, transported, used, controlled, stored, and monitored as prescribed by the most stringent rules promulgated by the provisions specified in federal, state, and other applicable local codes and ordinances. b. Where explosives are carried by public highway, the carriage shall be in accordance with 49 CFR 177. c. Overnight explosive storage is prohibited for this work. All unused explosives materials must be returned to the explosive supplier s or the Contractor s licensed off-site facilities after each blast. d. Security: The Blaster-in-Charge shall be responsible for ensuring the security of explosive materials at all times when explosive material are used or kept on the project site and the Blaster-in-Charge shall ensure that: Site Conditions 1. All persons that handle explosive materials, have control over them, or access to them, must not be prohibited persons, as defined in Section of 27 CFR (ATF Rules). 2. Copies of ATF Employee Possessor questionnaire forms (OMB No ) or ATF letters of clearance for all employees that will possess explosives for this work as defined in 27 CFR Part 555 must be available upon request by the appropriate authorities or the TxDOT Representative. Contractor and subcontractor employees, without submitted evidence of satisfactory ATF clearance, must not handle, control or have access to explosive materials. a. Existing Conditions and Requirements: The Contractor shall verify existing conditions and accept as is. Closeout Submittals a. On completion of the work, the Contractor shall furnish a written statement, countersigned by the Blaster-in-Charge, certifying that: 1. All blast holes charged with explosives and any other set explosive charges have been detonated, unloaded, or disposed of in an approved manner. 2. All blasting is complete

8 3. All explosive materials, including detonators, detonating cord, high and low explosives, deflagrating agents, and any unmixed components of a two-component explosive system, have been removed from the site. Materials a. Explosives and Initiation Systems: Use only explosives and detonators commercially manufactured within 12 months of the time of use. b. Only non-electric shocktube or electronic detonators shall be used. Use of cap and fuse or conventional electric detonators is prohibited. Execution a. General Requirements 1. Each working shift involving blasting shall have the Blaster-in-Charge on the site at all times. 2. Only pre-approved and experienced persons in accordance with federal, state and local laws, rules and regulations relating to the possession, handling, storage, transportation, and use of explosives, shall perform blasting operations and handling of explosives. 3. All work shall be performed in accordance with the Contractor s approved General, Safety, and Detailed Blast Plans 4. Review of the Contractor s blasting plan procedures or blast designs shall not relieve the Contractor of any of its responsibilities under the contract for ensuring the complete safety of its operations. Such review shall not waive any of the requirements of the Specifications nor relieve the Contractor of any regulation or permit obligation. 5. Drilling and blasting shall be performed carefully and skillfully to minimize overbreak and to preserve the surrounding structures outside the limits of the demolition in the soundest and most undisturbed condition within practical limits. 6. Excessive blasting will not be permitted. The Contractor, at its own expense shall remove any material outside the authorized cross section, which may be shattered or loosened because of blasting. The Contractor shall discontinue any method of blasting which leads to overshooting or is dangerous to the public or destructive to property or to natural features. 7. The Contractor shall be responsible for any damage or injury to any persons, property or structures resulting from handling, storage, or use of explosives. 8. Repair of Damages Due to Blasting: a. Repair/rebuild any injury or damage to the work or to existing pipes or structures at no additional cost to TxDOT

9 b. Safety Provisions b. Whenever blasting may damage adjacent rock, pipes, or structures, discontinue blasting and remove the rock by drilling, barring, wedging, or other methods. 1. Drilling and blasting shall ensure the safety of the work, the Contractor s employees and TxDOT s representatives, the public, and adjacent property, whether public or private, as required by BAAQMD approved ADMP, OSHA and Cal/OSHA and/or other agencies having jurisdiction. 2. All drill and blasting operations shall be performed in accordance with applicable fire prevention and control requirements of federal, state and local ordinances. 3. Erect proper warning signs of adequate number and size at all points of access to the area that 1) state that blasting operations are taking place in the area and 2) describe audible horn blasts for the 5-minute and 1-minute warnings, and the All Clear signal. 4. Establish and use an audible blast-warning system and use watchmen to ensure that all personnel in the area are properly warned and kept at a safe distance from the impending blast 5. Drill, load, tie-off, and detonate explosives under the direct supervision of a qualified and approved Blaster-in-Charge. 6. Following each blast, scaling shall be done to remove loose rock, fragments, or other potential rock falls. Scaling shall be completed prior to continuing with blasting. 7. A lightning detector shall be used to monitor the approach of lightning storms and in the event of such, the area will be evacuated and secured using procedures in the approved blasting safety plan. c. Preparation for Blasting and Notifications 1. After all required blasting submittals are approved the Contractor shall provide at least 24-hour-notice to the TxDOT Representative before the start of any initial blasting work in the site. 2. The Contractor shall notify the TxDOT Representative about the time of planned blasts at least two hours before they occur. No blasting shall occur unless the TxDOT Representative or his/her representative is present to observe the blast from a safe location. 3. At least two days before any explosive materials are brought to the site, the Contractor shall notify the Fort Worth Fire Department. Contact phone number is: (817) The Contractor shall abide by all referenced rules and regulations, and shall give special attention to the following specific rules: a. Clear blast area of unnecessary personnel and equipment before delivery of any explosives to the site

10 b. Provide a positive signal system to give adequate warning in every direction. Guard all access points, including water access, to the blast area to halt personnel and vehicles a safe distance from the blast. Maintain intercommunication between guards and person firing the blast, ensuring that the blast area is clear prior to firing. Guarding shall begin when loading begins, and shall continue until post-blast inspection has been made and the all-clear signal given. d. Suspension of Blasting Operations 1. Blasting operations may be suspended by the TxDOT Representative for any of the following reasons: a. Safety precautions taken are inadequate. b. Blasting Plan has not been approved c. Required records are not being kept. d. Adjacent improvements are damaged as a result of blasting. e. Blasting method endangers the stability of or causes damage to rock outside the prescribed limits of excavation. f. The results of the blasting are not acceptable to the TxDOT Representative. 2. Suspension of blasting operations shall in no way relieve the Contractor of their responsibilities under the terms of the Contract. Blasting operations shall not resume until modifications have been made to correct the conditions that resulted in suspension. No additional payments or time extensions will be made by TxDOT due to suspension of blasting operations. e. Blasting Limitations 1. Rock Excavation a. The use of explosives and blasting shall be as specified herein. No blasting will be permitted which, in the opinion of the TxDOT Representative, may be detrimental to existing installations. b. The diameter of drilled holes shall not exceed 3 inches. c. Loading densities of decoupled column charges in perimeter holes drilled along final rock slopes with walls steeper than 1/2:1 (H:V) shall not exceed 0.3 lb/ft. A bottom primer with weight not exceeding 0.5 lb may be used. d. Charge Confinement 1. All charges shall be crushed with clean crushed stone stemming sized from 3/8 to ¾ inches. 2. The amount of stemming shall be at least 25-charge-diameters. For example, if the charge diameter is 2 inches, minimum stemming is 50 inches (25 x 2) or 4.2 feet

11 3. The minimum distance between all charges and open rock or ground surfaces shall be at least 25-charge-diameters. e. Blast patterns shall be designed so that the explosive energy is directed towards the developed free face and not directed into the side of back walls of the excavation. f. Blasting shall only be conducted Monday through Friday during daylight hours. g. When water is present in blast holes, the Contractor shall select an explosives product that is not sensitive to propagation in wet ground. Specifications for the selected product shall be supplied in writing to the TxDOT Representative by the explosives manufacturer. Such specifications shall include sensitivity to propagation. h. The Contractor shall monitor all blasts for blast-induced ground vibration and air-blast overpressure. i. The Contractor shall conduct each blast only when a TxDOT Representative is present to witness the blast. f. Blasted Rock Containment 1. All blasts shall be covered with woven steel cable or steel-cable and rubber-tire blasting mats. Woven polypropylene or similar weed-barrier fabric, covered with at least 24 inches of soil or sand shall be placed over blast areas to protect initiators before mats are placed. Mats shall be overlapped at least 3 feet and shall completely cover the blast area and extend at least three feet beyond the blast area in all directions. If any flyrock or blasted material is thrown more than 10 feet or half the distance to the nearest structure, whichever is less, blasting shall be suspended until the Engineer has approved the Contractor's revised blasting plan showing revisions to the procedure adequate to reduce the flyrock. g. Monitoring 1. Ground Vibration and Air-Overpressure a. All vibration measuring equipment shall be used in accordance with the standards established by the Vibration Section of The International Society of Explosives Engineers (ISEE). b. Monitoring shall be done at three or more locations including on ground above the closest part of the existing storm drain, on ground next to the closest surface structure, and at one other location mutually agreed to by the Contractor and TxDOT Representative. c. A minimum of three approved seismographs shall be provided at specified locations to record particle velocity simultaneously along three mutually perpendicular axes and air-overpressure. The seismograph equipment shall be internally calibrated with a triaxial orthogonal velocity transducer with a flat frequency response from 2 to 200 Hz and a 2-Hz-response microphone. The equipment shall be capable of recording a permanent, real-time record

12 of blast-induced ground vibration and air-overpressure. The seismographs, calibrated within 12 months of the time of use, shall be operated by properly trained personnel. d. Seismographs shall have velocity transducers capable of measuring particle velocities as high as 8 ips and air-overpressure as high as 140 db (Linear scale). e. Intensity of air-overpressure measured adjacent to the nearest occupied surface structure shall not exceed 130 db (2 Hz Linear scale). f. Intensity of ground motion and minimum scaled distances shall conform to the following values. Location PPV (in/s) Minimum Scaled Distance (ft-lb -1/2 ) Residential Buildings Industrial Buildings Existing 9-9 Wide Arch Storm Drains Buried Pipes, Utilities, Conduits, and Drains Heavy Civil Concrete and Steel Structures Rail Road Lines