620.08 EXPLOSIVES.
(a) Permits. The contractor shall comply with all Federal, State or Municipal permits for transportation or use of explosives by his employees for blasting purposes.
(b) Handling Explosives; Personnel. Only persons duly authorized by the blaster shall in any way handle or use explosives.
(c) Smoking and Open Lights. Smoking, open lights or other flames are prohibited in any area included within a radius of twenty-five feet of any explosives magazine or 100 feet where explosives are being handled, used or temporarily kept.
(d) Explosives for Use.
(1) Any standard commercial explosives in good condition may be used for blasting except straight nitroglycerin dynamite, provided, that fifty percent nitroglycerin (ditching) dynamite may be used for ditch blasting by propagation.
(2) No explosive other than those in Fume Class I shall be used underground and then only as provided in Section 620.08(1) . No black powder or straight nitroglycerin dynamite shall be used. No frozen dynamite shall be used. All explosives used in a potentially gassy atmosphere shall be a type acceptable to the Municipal Engineer.
(e) Destroying Explosives. Explosives which have deteriorated or have been damaged so that they have become unfit for use shall be destroyed by a qualified person experienced in this work and designated by the superintendent or contractor.
(f) Operations During Electrical Storms.
(1) All use of explosives and any handling thereof shall be stopped immediately upon the approach of a thunderstorm and all personnel in the area shall immediately seek a place of safety in a proper location designated by the superintendent or his representative.
(2) All transportation of explosives on the surface or underground and any handling incident thereto shall be stopped immediately upon the approach of an electrical storm, and all persons shall immediately retire to a place of safety. Persons underground shall be notified of the approach and cessation of an electrical storm by means of signals on the general lighting circuit. Such signals shall consist of four periods of darkness, each of five seconds duration, as a warning, and two periods of darkness, each of five seconds duration, to indicate all clear. In shafts, tunnels or other excavations handling of explosives, loading of holes, connecting up or firing of charges shall not be performed during an electrical storm, and all persons shall withdraw to a safe distance from a partially or totally loaded face. The foregoing notwithstanding, explosives shall not be left at the top of a shaft during such storm, but shall be removed to a safe distance.
(g) Transportation. Any vehicle transporting explosives either on the public highway or on the construction area over which the contractor exercises control shall comply with State rules and regulations governing transportation of explosives. Access for vehicles to magazines shall be by a good, clean, even, traveled way which shall likewise be provided between the storage magazine and the site of blasting operations.
(h) Storage.
(1) The location and construction of every magazine shall be approved by the Chief of Police and any explosives that are stored therein and required permits issued therefor shall be posted in such magazines.
(Ord. 1968-5. Passed 2-27-68.)
(2) The contractor and/or blaster shall store all explosives in magazines as instructed by the Chief of Police or by a person designated by him.
(Ord. 1978-12. Passed 5-9-78.)
(3) All magazines and all enclosures used for explosives shall be kept locked at all times except while placing explosives therein, removing explosives therefrom or while cleaning or during inspections. Such magazines shall be under the immediate charge of a reliable, competent person who shall be assigned no conflicting duties.
(4) Only persons authorized by the superintendent shall have access to magazines.
(5) Detonators shall be stored in a separate magazine and no other explosives, materials or tools except a wooden wedge and wooden mallet shall be stored in such magazines.
(6) All explosives, other than detonators, shall be stored in a separate magazine devoted exclusively to such explosives.
(7) When not in use all blasting equipment and loading tools used in connection with blasting shall be stored in a separate place, compartment or enclosure devoted to such purpose and so constructed as to keep such equipment and tools in good working condition at all times.
(8) All magazines shall be so located and so protected as to prevent accidental impact from vehicles or falling objects.
(9) Every magazine and the area surrounding it shall be kept clean at all times and free from particles of explosives. Such magazine shall also be kept cool and dry.
(10) Every magazine shall be painted a bright red of a shade and hue approved by the Chief of Police.
(11) Every magazine shall be protected against approach or interference by unauthorized persons.
(12) Artificial lighting of the area surrounding the magazines shall be by floodlights. No lights shall be permitted in a magazine except electric flash lights or electric lanterns, so constructed that it will not be possible to obtain a difference of potential between any two points on the outside of the lamp casing.
(13) In using explosives those of appropriate kind that have been longest in the magazine shall be stacked no more than six feet high and in a manner to insure using first those of appropriate grades and kinds that have been longest in storage.
(14) Packages of explosives shall not be opened at any point less than fifty feet distant from any magazine. No tools except wooden, and wooden, fibre or rubber mallets shall be used for opening packages of explosives except that nonferrous slitters may be used for opening fibre board containers, provided such slitters cannot come within range of metallic case fasteners.
(15) Doors.
A. Doors of all Class A magazines shall be equipped with two mortise locks, with two padlocks fastened in separate clasps and staples, with a combination of a mortise lock and a padlock, with a mortise lock that requires two keys to open or with a three- point lock. Padlocks and mortise locks shall be the equivalent of a five tumbler jar-proof lock.
B. Any padlock on a Class A magazine shall be protected with approved one fourth inch steel approved cups so constructed as to positively prevent lever action on the lock or clasp.
C. Doors shall be provided with strong hinged clasps, and staples attached by welds, rivets or by bolts fitted with locks, washers and nuts on the inside of the magazine, and installed in such a manner that the fastening cannot be removed when the magazine door is closed and locked and that metal is not exposed on the inside surface. Doors shall be bullet-resistant and constructed of not less than three thicknesses of seven-eighths of an inch matched hardwood, covered on the outside with three-eighths of an inch steel plate.
D. Openings shall be provided only for entrance and ventilation. Ventilators at the base of walls shall be constructed with offsets and heavily screened. Those in the roof and at the eaves shall be screened to prevent sparks from entering.
(16) All magazines shall be either of fireproof or flame-resistant construction.
(17) Signs.
A. The premises on which a permanent magazine is located shall be conspicuously marked by signs containing the words "EXPLOSIVES-KEEP OFF". Such signs shall adequately warn any person approaching the magazine of the presence of explosives, but the sign shall not be so placed as to direct general public attention to the location of the magazine.
B. No signs shall be placed on surface magazines or barricades, or be so located that a bullet passing directly through the face of the sign will strike the magazine.
(18) The area surrounding a magazine for not less than fifty feet in all directions shall be kept free of rubbish, dry grass or other combustible material.
(19) Underground supply. No greater quantity of explosives than that which is required for immediate use shall be taken or kept underground.
(20) Temporary retention underground. Small quantities of explosives resulting from over estimate of the amount necessary for the blast may be temporarily retained underground until after the blast but only if placed in a limited capacity daily supply magazine situated at a safe distance from the tunnel face. Detonators shall not be placed in the same receptacle with other explosives.
(i) Use.
(1) Blasting operations shall be carried on with the smallest possible number of persons present.
(2) The diameter of explosives cartridges shall be of an appropriate size to permit charging drill holes throughout their lengths without either forcing or ramming explosives.
(3) Explosives should not be removed from the original wrapper before being loaded into bore holes except when irregularities of the hole make it impossible to load whole cartridges with safety or in block holing where small charges are desirable. This rule shall not apply to free running explosives.
(4) Excessive ramming should be avoided in loading or tamping explosives in a bore hole. In tamping only wooden tools of suitable diameter with squarecut ends and without exposed metal parts shall be used. Plastic pipe with a wooden plug at the end should be used for long, small diameter holes. When a tamping stick is used in charging drill holes, the force of impact shall be insufficient to penetrate explosive cartridges. Primed cartridges shall not be tamped.
(5) No activity of a continuous nature, nor more than two men engaged in intermittent work, shall be permitted in front of a face being loaded with explosives and within the probable range of flying material in the case of a premature blast:
A. When steam equipment is being employed; or
B. When primers containing electric blasting caps are employed the probable range of flying material shall be considered to be not less than 100 feet to one and one-half times the height of the face of the rock cut whichever is greater provided that end clearance may be reduced by one-half.
(6) When loading free running or bulk explosives, a bronze, wooden or heavy paper funnel shall be used unless the explosives can be poured directly from a container into the hole in such a manner as to prevent scattering of loose explosives around the collar of the hole. The use of mechanical or pneumatic methods of loading shall be prohibited.
(7) Primers shall not be made up until just prior to loading into the hole.
A. Electric blasting caps used in churn drill holes or any small bore holes shall always be tested with a blasting galvanometer before any stemming is placed in the hole, and also during loading whenever any question arises as to the condition of the leg wires. The leg wires shall be short circuited after testing and shall remain so until they are connected with the circuit.
B. In short length small diameter bore holes containing only one electric blasting cap the leg-wire shunt shall be left in place until connection is made either into the completed circuit or the leading wires are coiled near the blasting area and shunted at the power connection circuit or the leading wires are coiled near the blasting area and shunted at the power connection end. Leading wires shall always be in the blaster's possession, uncoiled or strung toward the power source, not grounded and before connection is made the circuit shall be tested with a blasting galvanometer. If the circuit is defective the leading wires shall be reshunted and recoiled to the blasting area before investigating for the trouble. If a defective cap or leg-wire occurs in a bore hole the stemming shall be removed by compressed air or a water jet and a new primer inserted.
C. In any single series and in the same blast, electric blasting caps shall be the same brand.
(8) No blast shall be fired until the rock or other substances to be loosened or shattered has been covered with strong woven matting of rope or wire and a number of heavy logs or timbers securely tied together by chains or cables or sufficient weight to prevent the scattering of the loosened or shattered material. Displacement of such matting due to detonation shall be kept to a minimum. Extreme care shall be exercised at all times to prevent rock slides due to excessive vibration. The provisions herein may be waived by the Municipal Engineer when in his opinion the use of matting is unnecessary. (Ord. 1968-5. Passed 2-27-68.)
(9) Blasts shall only be fired electrically with either a power circuit or blasting machine excepting that individual holes may be initiated with electrical firing devices or detonating fuses. The method of fire shall at all times be maintained in good operating condition. The efficiency of the blasting machine shall be tested periodically to make certain that it can deliver power at its rated capacity. The power circuit shall be energized by not less than 200 volts nor more than 500 volts. For alternating current, not less than forty cycles per second shall be used.
(10) When firing from a power circuit, sufficient power shall be provided to supply ample current and voltage requirements for each blast. When firing with a blasting machine, it shall be used for series or parallel series circuits and be approved therefor. The explosives manufacturer's instructions shall be followed for all electric blasting regardless of source of power.
(11) The power wires, leading wires and connecting wires shall be thoroughly insulated and kept from contact with any electrical conductor, air lines or pools of water or oil.
(12) The leg wires of detonators shall be kept short circuited until connected into either the circuit or to the shunted leading wires. All bare connections shall be either taped or blocked up in position so as to prevent current leakage or entrance of stray or active currents. While making connections in the blast area the leading wires shall be kept short circuited at the power source end but not grounded and shall remain in the possession of the blaster. The leading wires shall then be strung from the blast area toward the source of power to make the final connections to fire the blast. Before connecting the leading wires to the power circuit, the blaster shall make certain by a blasting galvanometer test that an unsafe difference in potential does not exist between the two wires of a blasting line. If this test shows either a short circuit or no circuit, the reshunted leading wires shall be recoiled to the blast area before investigating for the trouble.
(13) Positive steps shall be taken to prevent lead wires from being dislodged and making contact with overhead high voltage electric power lines. Should accidental contact be made, the blaster shall prevent any person from touching the blasting device and he shall immediately clear the area of all persons. No person shall enter the area until the blaster has notified the owner of the power line and the latter has eliminated the danger of electric shock.
(14) A power circuit used for firing shall be controlled by a switch located at a safe distance to be determined by the blaster but not less than 150 feet from the blast area. Such switch when in actual use shall be firmly fastened in position, thoroughly insulated against grounds and wholly enclosed in a tight box that shall be kept closed and locked at all times except while firing. No person other than the blaster shall have access to the switch. The switch shall be provided with a short circuit in the "off" position and shall be so arranged that the box enclosure can be locked only when the switch is in the "off" position.
(15) When firing by means of a power circuit the blasting circuit shall at all times be broken in at least one place by a gap of at least five feet on the incoming side of the switch, except during the firing operation.
(16) When firing with a blasting machine, it shall be located not less than 150 feet from the blast area.
(17) When firing by means of a blasting machine, the leading wires shall be kept short circuited until the shot is ready for firing and shall not be connected to the blasting machine until immediately before the time of firing and shall be disconnected from the blasting machine and short circuited immediately after firing.
(18) Electric detonators and blasting circuits shall be tested only by means of a blasting galvanometer designed for this purpose.
(19) Required warnings.
A. (1) Before firing any blast all means of access to the danger zone, the extent of which shall be determined by the blaster, shall be effectively guarded to exclude all unauthorized personnel. At least one minute, but not more than two minutes before the detonation of a blast, the blaster in charge, or someone directed by the blaster, shall give an audible warning signal. If the blast is not detonated within two minutes of the audible warning signal, the warning signal shall be repeated as required by this paragraph before the blast is detonated. Upon the sounding of the warning signal, all persons shall retire to a safe shelter. No blast shall be fired while any person is in the danger zone. After the blast has been detonated and the blaster has determined that the blast area is safe to re-enter, an audible all-clear signal shall be given. Warning and all-clear signals shall be different in character and audible within one-quarter mile of the blasting site.
(2) The blaster shall use standard warning and all-clear signals to be produced by an air horn or similar device. The warning signal, to be sounded one to two minutes before the blast, shall consist of three long reports, each lasting at least five seconds. The all-clear signal shall consist of one long report lasting at least five seconds.
(Ord. 1999-31. Passed 10-12-99.)
B. It shall be the responsibility of the contractor to safeguard pedestrians and other highway users and their vehicles from injury or damage due to blasting operations. When the blast area is within 300 feet of a highway, the blaster, just prior to the blast shall designate a sufficient number of employees of the contractor, each carrying an approved red warning flag or sign, to stop all vehicular and pedestrian traffic on each possible route of travel in the vicinity of the blast area until the blast has been fired. Qualified employees shall be dispatched to predetermined points on the highways to prevent vehicles from entering the danger zone. A check shall be made of the highways in the danger zone to insure that there are no parked vehicles or pedestrians who would be endangered by the blast.
(20) When the floor of a rock cut is more than five feet below the average grade of a public highway at any point within 100 feet of such highway, an effective and approved barrier shall be erected by the contractor along the property line nearest the highway for an approved distance to provide protection against the drop or fall on vehicles or persons.
(21) Immediately following the blast the area shall be examined by the blaster for evidence of misfired charges. If such is found, the blaster shall provide proper safeguards for excluding all personnel from the danger zone except minimum personnel which, in the opinion of the blaster are required to remove the misfire.
(22) All misfires shall be reported at once to the superintendent who shall then determine the safe and proper method of disposal. Each misfire presents an individual problem which shall be placed under the supervision of a person thoroughly competent to handle such matters. The unexploded charge shall be detonated if such can be accomplished without risk of injury to personnel. If repriming is necessary any stemming present in the hole may be removed by a jet of water or air. In cases where competent supervision is not available locally, the explosives manufacturer shall be consulted as to availability thereof.
(23) Drilling in any hole that is known to contain or have contained explosives is prohibited until satisfactory neutralization is effected.
(24) A complete record shall be kept showing all misfires, their courses and method of disposal. Copies shall be furnished to the Chief of Police within one day.
(25) In case of a sprung hole or where a charge fires but does not bring down the burden, it is permissible to reload the bore hole if in suitable condition to perform its functions and only after the temperature of the hole has been reduced by water or otherwise to not more than 150 degrees F. (Ord. 1968-3. Passed 1-12-68.)
(26) Stemming.
A. Each blast hole shall be stemmed to the collar or be high enough to provide efficient confinement of the charge and to minimize the chance of injury to personnel and adjoining property from flying material.
B. For toe holes the collar stemming shall in no case be less than one-third the depth of the hole. (Ord. 1999-31. Passed 10-12-99.)
(27) Block holes shall contain at least eighty- five percent of stemming material.
(28) There shall be compliance with the following requirements to eliminate the hazards of radio-frequency energy in connection with the use of electric blasting caps.
A. Irrespective of ownership mobile transmitting stations with outputs up to thirty watts such as those of the portable type or installed in automobiles shall be kept at least 100 feet away from any electric blasting cap except when in original containers. Users of such stations shall be notified by the contractor and such users shall comply with the requirements of this subparagraph.
B. When such radio transmitters are less than 100 feet away from electric blasting caps in other than original containers they shall be de-energized and should be effectively locked.
C. When electric blasting caps are transported in a motor vehicle equipped with a radio transmitter, they shall either be in their original package or stored in a closed metal box that is lined with a cushioning material such as wood or sponge rubber. When the electric blasting caps are being placed into or removed from the box, the transmitter circuit shall be disconnected.
D. All blasting operations shall be conducted at no less distance from any fixed or mobile radio transmitter than indicated in the following table:
Transmitter power output (watts) | Minimum distance from blasting operations using electric blasting caps (feet) |
5 - 25 | 100 |
25 - 50 | 150 |
50 - 100 | 220 |
100 - 250 | 350 |
250 - 500 | 450 |
500 - 1,000 | 650 |
1,000 - 2,500 | 1,000 |
2,500 - 5,000 | 1,500 |
5,000 - 10,000 | 2,200 |
10,000 - 25,000 | 3,500 |
25,000 - 50,000 | 5,000 |
50,000 - 100,000 | 7,000 |
E. When it can be demonstrated by means of approved tests that electric blasting may be carried out at lesser distances from the transmitter than required by the table shown in subsection (i)(28)D. hereof, the Service Director may allow a variation from the requirements of such table.
(29) Short period delay firing shall be used when necessary to comply with the requirements of Section 620.09.
(30) Transportation from surface. The supply of explosives shall be transported from the magazine on the surface without interruption directly to the heading of the tunnel and no person except the attendant shall ride with the supply of explosives.
(31) Transportation on cage, skip or bucket. Detonators and other explosives shall not be transported at the same time on the cage, skip or bucket.
(32) Distribution underground. Where cars are necessary separate insulated containers or compartments in the same car shall be provided for carrying detonators apart from other explosives underground. Such cars shall be painted red and clearly labeled as to contents. Receptacles specially designed for the purpose and having a capacity not in excess of fifty pounds shall be used for carrying explosives to the face. The amount of explosives carried to the face shall not exceed the amount estimated to be necessary for the blast.
(33) Primers. Primers shall be made up near the face at special benches provided for the purpose. They must be kept in insulated carriers or containers separate from other explosives at all times until placed in bore holes. Primers shall be made up immediately prior to their use in the blast and the number of such primers shall not be more than is necessary for such blast.
(j) Primary Blasting.
(1) While explosives are being loaded in bore holes, the blaster shall keep all persons not necessary for the blasting operation away from the blast area.
(2) When loading a blast primed with electric detonators, explosives shall not be transported into the blast area until all electric power circuits have first been disconnected to a point not less than 100 feet from the blast area.
(3) When drilling and loading are being performed simultaneously in the same general area, the two operations shall be separated as widely as practicable and in no case shall drilling be conducted closer to a loaded hole or a hole that is being loaded than a distance equal to the deepest blast hole in the area, and in no case less than fifty feet. Loading and drilling operations shall not be permitted or allowed underground in the same general working area.
(4) Holes shall be checked prior to loading to determine depth and condition. After any explosives have been loaded all measuring shall be done with a cloth tape, nonferrous measuring device and lead plumb bob or a wooden tamping pole or wooden dolly free of exposed metal parts, as appropriate for vertical holes.
(5) Loading of explosives, amount in blast area.
A. Under no circumstances shall the amount of explosives taken into a blast area exceed the amount estimated by the blaster as necessary for the blast. Such explosives shall be stacked in piles at least twenty-five feet from the nearest holes being loaded or as far as the width of the bench or floor permits, and at such distances apart that any premature explosion will not be likely to propagate from one pile to another, as provided in subsection (j)(5)C. herein.
B. The explosives containers, if any, shall be opened at the pile and carried up to the hole one case or unit at a time for immediate loading or placed at a loading station not less than six feet from the hole except that not more than 100 pounds of explosives shall be allowed at the loading station at any one time.
C. Explosives shall be distributed in such a manner that the distances from storage piles to the allowable maximum quantity of 100 pounds of explosives at the loading station or between such 100 pound loading station piles shall not be less than the quantities shown in the following quantity distance table:
Pounds of explosives | Distance between piles of explosives in feet |
Up to 50 | 21 |
100 | 25 |
200 | 32 |
300 | 37 |
400 | 41 |
500 | 44 |
750 | 50 |
1,000 | 55 |
1,500 | 64 |
2,000 | 70 |
2,500 | 75 |
5,000 | 96 |
10,000 | 123 |
Note: Interpolation is permitted.
(6) Blasting operations shall be carried on with the smallest practical number of persons present and no one but authorized personnel shall be allowed in or near the blast area.
(7) Drill holes shall not be sprung when they are less than 100 feet from the nearest hole containing explosives. Holes that have been sprung shall not be charged with explosives until the maximum temperature in any portion of such holes has been reduced to 150 degrees F. Where practical the use of water is recommended for cooling purposes.
(8) When loading a blast primed with detonating fuse, the detonator or detonators required for firing the blast shall not be brought into the blast area not attached to the detonating fuse until all persons except the blaster and his assistants, have been cleared from the danger zone and retreated to a safe distance or to a place of safe shelter.
(9) In all primary blasting and all other blasting where the firing of any one hole is likely to break into or damage another hole in the vicinity or where the firing of any hole may propagate the charge in a loaded hole in the vicinity, all holes which have been loaded shall be included and fired in the blast.
(10) All holes for blasting shall be checked before attempting to load explosives. Blast holes may be checked with a dolly or tamping block or by visual inspection with the aid of a mirror.
(11) Water standing in blast holes should be bailed out if possible and the holes shall be loaded with an explosives water resistance.
(12) Blasting crews shall consist of the minimum number of experienced men to do the work in an efficient manner, and should be organized carefully with each man assigned to definite tasks in order to avoid confusion.
(13) Loading chart for primary blasting.
A. A blast shall be planned before loading is started. The planned charge for each hole shall be recorded.
B. The condition of each hole to be loaded and the amount, height and position of the explosives charge or charges placed in the hole shall be recorded on the loading chart.
(14) Members of loading crews engaged in loading blast holes should be prohibited from wearing hobnail or steel-plated shoes to avoid striking sparks on rocks.
(15) Large dynamite cartridges may be dropped in blast holes only when the hole is free from obstructions to the depth at which the cartridge is to rest.
(16) Large dynamite cartridges shall not be dropped in blast holes containing excessive water until the charge is above the water level.
(17) Large dynamite cartridges that have been wedged in a blast hole shall not be tamped. After pouring water into the hole, attempts to dislodge or pierce them shall be made with a spear-shaped wooden tamping block or a small diameter wooden pole.
(18) Rough or ragged holes and holes partly closed by an obstruction that cannot be readily removed shall be loaded with cartridged dynamite lowered with a rope, with free running powder, or with dynamite cut in small pieces.
(19) When loading a long line of holes with more than one loading crew, the crews shall be separated by the greatest practical distance which can be maintained as the loading operations progress and which is consistent with efficient operation and supervision of the crews. Every effort shall be made to keep the loading crews a minimum of twenty-five feet apart and to prevent the simultaneous loading of adjacent holes.
(20) Excessively large amounts of explosives shall not be delivered to the loading area at one time. If deliveries of explosives are made by truck, the quantity permitted at or near the loading operations shall be limited to one truck load. Other trucks loaded with explosives shall wait or be unloaded in separate safe places away from the loading operations.
(21) Explosives should be delivered first to the holes farthest from the truck to avoid driving or walking among the piles of explosives.
(22) Explosives in excess of immediate requirements when removed from the main storage magazine and delivered in the vicinity of a blasting operation shall be stored in a Class A magazine.
(23) Sufficient suitable stemming or tamping material shall be placed by each hole before the delivery of explosives to the holes is started.
(24) Stemming shall be placed in each hole with care to avoid damage to the detonating fuse or leg wires of electric detonators.
(25) Only holes which are to be blasted immediately shall be loaded.
(26) Detonating fuse.
A. All detonating fuses shall be covered with maximum stemming where physically possible.
B. When priming blast holes with detonating fuse, it shall be lowered to the bottom of the hole either by attaching it to the first cartridge or by other means. After allowance for settlement, it shall then be cut from the reel and the reel moved well away or to the next hole before any other explosives are loaded.
1. Where rigidly encased, large-diameter explosives cartridges are used, a cartridge primed with detonating fuse may be placed near the bottom or any intermediate point. With large continuous charges two or more primed cartridges should be used.
2. If foreign matter, such as dirt or stones, should fall into a hole while priming an explosive column with rigidly encased, large diameter explosive cartridges and disturbs cartridge contact an additional primed cartridge should be placed before continuing to charge the hole.
C. The detonating fuse shall extend from the hole a distance of one or two feet more than sufficient to compensate for any subsidence, should be drawn taut and made secure on the top where it will not interfere with loading operations or come in contact with explosives on the ground.
D. It shall be checked each time before stemming material is used to see that it has not been broken.
E. When detonating fuse is used, main trunk line splices shall be factory splices or tight square knots. No splices shall be used in the drill hole.
F. All branch line connections and all connections in the main line other than splices shall be tight and at right angles.
G. The main or trunk line shall be laid out free of kinks or coils and all connections shall be inspected before firing the blast.
H. When connecting an electric blasting cap to detonating fuse, the type of connection used shall be in accordance with the manufacturer's instructions. Two electric detonators separated by tape should be taped in direct contact with the detonating fuse with their charged ends pointing in the direction of detonating travel.
I. Detonators shall not be brought to the loading area nor attached to the detonating fuse until all is in readiness to fire the blast.
J. A plain detonating fuse may be used for trunk lines or in shallow drill holes but reinforced or wire countered types shall be used in deep or ragged holes.
(27) Toe hole blasting.
A. The charge of explosives shall be pushed to the end of the hole with a wooden pole using care not to block the hole.
B. Care shall be used in placing stemming in the hole especially if loose explosives are on the bottom of the flat hole.
C. Only wooden poles shall be used in loading snake holes.
(28) Wagon drill hole blasting.
A. The same precautions shall be followed in loading small diameter drill holes, such as wagon drill and jack hammer holes, as in loading larger diameter holes.
B. When wagon drill holes or smaller diameter bore holes are to be loaded for blasting, the explosives containers shall be stacked in piles out of line with and at least twenty-five feet from the nearest drill hole to be loaded.
C. The containers shall be opened at the piles as needed and the opened explosives cases carried one at a time to the loading crew. The amount of explosives at one hole shall be limited to 100 pounds. Empty cases and lining paper shall be removed immediately to a waste pile. Since empty cases or case linings may still contain explosives material, they shall be burned in the open in a place where there will be no likelihood of damage to personnel or property, and, as the fire is lighted, all personnel shall retire to a safe distance from the burning pile until it has been completely burned.
(29) Quantities of explosives that may be used in primary blasting shall be governed by allowable limits as set forth in these rules and regulations.
(k) Secondary Blasting.
(1) Oversize fragments shall be reduced to shovel size by use of the ball method, except as otherwise directed by the Service Director.
(2) Mud capping shall be prohibited except where written approval for an exception has been received from the Service Director and then only where areas are sparsely settled.
(3) No tools or equipment or activity of any kind shall be permitted on a muck pile directly above a blaster while he is loading explosives into holes.
(4) Charges of explosives shall be confined in all cases by suitable stemming material.
(5) No person except the blaster and any others directly engaged in loading holes shall be permitted within the immediate area while loading is being performed. Loading of any hole shall be completed in one continuous operation including insertion of the primer and the stemming.
(6) Not more than ten pounds of explosives shall be detonated at any one time in a secondary shot provided however that trench shots shall be governed by the requirements of Section 620.06.
(l) Control of Toxic Gases.
(1) This subsection shall apply to operations in shafts and tunnels.
(2) Explosives, fume classification.
A. Determination of fume classification. The fume classification of an explosive shall be determined from the total volume of carbon monoxide and hydrogen sulfide emitted in the Bichel gage by one, one and one-fourth by eight-inch cartridge of the explosive to be tested. The standard procedure of the Federal Bureau of Mines, modified to give results in terms of cubic feet per cartridge of explosive, shall be used. This is as follows:
One cartridge of the explosive one and one fourth by eight inches or smaller, in its original wrapper, is fired in the Bichel gage. A gage of the Bourdon type is substituted for the regular indicator mechanism. This Bourdon gage is connected to the chamber of the bomb after the shot is fired. Before the shot is fired the bomb is evacuated until a vacuum of fifty plus or minus five mm. is obtained. The vacuum data used are the difference between the barometer reading for the atmosphere and the manometer reading for the gage. In order that the testing engineer may be assured of obtaining a vacuum and that there may be no clogged lines, the valve connection for the pressure for the pressure gage on top of the bomb should be left open until the vacuum pump has been started and air is sucking through the valve. The charge is fired by means of a No. 6 electric detonator embedded in the charge within the bomb. Five minutes after the shot is fired the stopcock, which intervenes between the bomb and the Bourdon gage is opened and the pressure noted. When the gage reading is obtained the gaseous products within the gage have cooled to approximately room temperature. The volume of the gases and vapors at O° C. and at a pressure of 760 mm. of mercury is calculated from the data obtained, which comprise gage temperature, gage pressure, barometric pressure and volume of the bomb (approximately fifteen litters).
One-half hour after the shot is fired a sample of the gases and vapors is taken through the valve to which the air pump was attached. The gases are allowed to escape from the gage slowly by cracking the valve, and a 200-cc. sample is thereby collected over mercury in the aspirator is allowed to run out, and the gases and vapors that follow it are drawn off until the pressure within the bomb is reduced to that of the atmosphere; therefore, the sample of gases and vapors taken is a differential one.
The gaseous products are analyzed by means of an Orsat apparatus, and the amounts of carbon dioxide, oxygen, carbon monoxide, hydrogen, methane, nitrogen and hydrogen sulfide are determined. The amounts of these gases are calculated to cubic feet per cartridge of explosive. The average result of three analyses is accepted if the average deviation from the mean is less than plus or minus 1.25 percent; otherwise, further analyses are made until the above criterion is satisfied or until six analyses have been made, in which latter instance the average of the six is accepted.
A second calculation is made to determine whether the amount of oxygen in the gaseous products is more than adequate to burn the combustible gases to their maximum oxidizable state, that is, hydrogen to water, methane to water and carbon dioxide and hydrogen sulfide to water and sulfur trioxide.
B. Fume classes. The amount of poisonous gases produced per one and one-fourth by eight-inch cartridge shall be as follows:
Fume Class | Cubic Feet |
1 | less than 0.16 |
2 | 0.16 to 0.333 |
3 | 0.33 to 0.67 |
Cartridges of explosives eight inches in length that are smaller in diameter than one and one-fourth inches shall comply with the limit specified for the fume class of the one and one-fourth by eight-inch cartridge. For cartridges smaller than eight inches in length and one and one-fourth inches or less in diameter the amounts of poisonous gases produced in the Bichel gage are computed by proportion to a length of eight inches, and this latter figure shall comply with the limit specified for the fume class of the one and one-fourth by eight-inch cartridge.
For cartridges of any length and of diameter greater than one and one-fourth inches the amounts of poisonous gases produced in the Bichel gage are computed by proportion to the weight of a one and one-fourth by eight inch cartridge; this latter figure shall comply with the limit specified for the fume class of the one and one-fourth by eight-inch cartridge.
C. Designation on container. All cases containing explosives for underground use shall be clearly marked in one-fourth of an inch or larger letters with the appropriate fume classification.
(3) Explosives for use underground.
A. Limitation of fume class. No explosive other than those in fume Class I shall be used in any shaft or tunnel.
B. Excess oxygen in gases produced. No explosive shall be used underground if the gases emitted in the Bichel gage in tests described under subsection (l)(2)B. hereof contain more oxygen than is necessary to burn the combustible gases to their maximum oxidizable state.
C. Minimum size of cartridge. Explosives packed in cartridges less than one inch in diameter shall not be used underground.
D. Deterioration. Explosives that show obvious deterioration, such as incrustation of salts, exudation of liquids or extreme hardening or softening shall not be used.
(4) Control of atmospheres underground.
A. Ventilation. Controlled ventilation shall be provided where gases are produced by blasting or where inflammable gases are present.
B. Method of determining carbon monoxide. The standard method of determining the concentration of carbon monoxide present shall be an approved method.
C. Entering for short durations. An employee may enter for a period not to exceed five minutes, concentrations of not more than 0.10 percent by volume of carbon monoxide or, for a period not to exceed fifteen minutes, concentrations of not more than 0.06 percent by volume.
D. Entering for prolonged time. When an employee enters with the intention of remaining, ventilating must be maintained so that the air breathed shall not exceed the following:
Carbon Monoxide | Percent by Volume |
At time of entrance up to 60 minutes
| 0.030
|
60 minutes after entrance up to 120 minutes
| .015
|
120 minutes after entrance and thereafter
| .010
|
E. Use of respirators. When the concentration of carbon monoxide or the time of exposure exceeds the requirements of subsection (4)C. hereof, approved respiratory protection shall be provided for and used by every employee entering underground.
F. Method of determining inflammable gas. The standard method of determining inflammable gas shall be by an approved means.
G. Presence of inflammable gas. Blasting with explosives is prohibited in places where the concentration of inflammable gas exceeds one and one-half percent by volume.
H. Supervision. The contractor or operator shall designate an employee whose duties it shall be:
1. To make tests to determine the concentrations of inflammable gas;
2. To make tests to determine the concentrations of poisonous gases;
3. To control the entrance and period of exposure of persons entering underground.
The employee so designated shall be provided with an approved gas mask at the time such tests are made.
The employee so designated shall keep a dated record of all tests, which shall be on approved forms and available at all times.
(Ord. 1968-3. Passed 1-12-68.)
(m) Whoever violates or fails to comply with any of the provisions of this section is guilty of a misdemeanor of the third degree. Punishment shall be as provided in Section 698.02. A separate offense shall be deemed committed each day during or on which a violation occurs or continues.