816.64(a)(1).

Blasting Schedule Publication

A. Several commenters objected to the provisions in the proposed regulations requiring the mining operation to publish its blasting schedule in a local newspaper at least 10 days, but not more than 20 days, prior to blasting. A review of the comments resulted in consideration of the alternatives listed below. Alternative 1 was adopted by the Office.

1. Retain Section 816.64(a)(1) as proposed.

2. Allow publication of the blasting schedule at the same time that notification of the filing of the permit application is published.

3. Do not require public notification of the blasting schedule and delete Section 816.64(a)(1).

4. Delete the requirement for publishing the blasting schedule in a newspaper, but retain the requirement for notification by mail.

5. Require notification of the blasting schedule only in "heavily populated areas.''

B.

Analyses of Comments and Alternatives.

Alternative 2.

One commenter stated that the permittee should be allowed to publish the blasting schedule at the same time as the notice of the filing of the permit applicaton is published in a newspaper under Section 513(a) of the Act and 30 CFR 786.11. The commenter reasoned that, since it is impossible to predict when a permit to mine will be granted, rerunning the newspaper notice and performing the mailings within the proposed rule's prescribed time would be very difficult to predict.

If this comment were adopted, the schedule published at the time of the filing of the permit application would be likely impossible to predict since it would not be known when the permit would be granted and, therefore, the applicant could not publish with reasonable specificity the date when blasting was planned to start. Moreover, as is explained in detail in the preamble to 30 CFR 780.13, permit applications will ordinarily not contain detailed information on proposed blasting activities. Hence, the applicant will not have the data available at that point with which to sufficiently warn the public. Alternatively, the operator can be specific, after the permit has been issued and before publishing the blasting schedule, so as to adequately warn the public of when blasting, in fact, will be conducted.

Alternative 3.

It was asserted by a commenter that publication of the blasting schedule is unnecessary and dangerous to mine personnel who might rush operations to meet the schedule. Publication of the blasting schedule is required by Section 515(b)(A) of the Act and the schedule can be planned in accordance with Section 816.64(b) of the regulations so that it does not increase the danger to mine personnel, by selecting certain periods during several hours of the day for detonations of the blasts. If a case did occur that a blast was not ready to be detonated at the time originally anticipated, it could be detonated during the next scheduled detonation period.

Moreover, Section 816.65(a) of the final rules allows for detonations to be made in deviation from the schedule published in the newspaper, under carefully prescribed circumstances, to avoid a safety hazard to workers. Finally, Section 816.64(a)(1) does not prohibit loading of blasts at any time during the daylight hours; the schedule requirement refers only to periods of time when detonations are actually conducted.

Alternative 4.

Another commenter agreed with the notification of the blasting schedule by mail, but objected to the requirement of publishing the notice in the newspaper. Section 515(b)(15)(A) of the Act, however, specifically requires publishing the schedule "in a newspaper of general circulation in the locality.'' Further, persons traveling through an area near blasting need to be aware of the times of blasting through newspaper notices, in addition to residents of those areas notified by mail.

Alternative 5.

One commenter agreed with requiring public notice of the blasting schedule in heavily populated areas, but objected this was impractical in remote areas. The Office decided not to modify the regulation. Notification in remote areas will require considerably less effort to conform with the Act, due to the probability of fewer residents within one-half mile of the blasting site who require notification by mail. In any event, the Act requires notification without regard to the density of population in the areas involved.

Section 816.64(a)(2) A. Many comments were received on details of the mailing of the blast schedule and notification of how to request a preblast survey to owners and residents within one-half mile of the blast site. A review of the comments resulted in consideration of the alternatives listed below. Alternatives 3 and 4 were adopted by the Office.

1. Retain Section 816.64(a)(2) as proposed.

2. Change "permit area'' to "blasting site.'' 3. Restrict the meaning of "permit area''.

4. Add a provision to Section 816.64(c), eliminating the requirement for preblast survey information in change notices.

{15185}B.

Analyses of Comments and Alternatives.

Alternatives 2 and 3.

Several commenters pointed out that Section 515(b)(15)(a) of the Act provides that residents within a half mile of the "blasting site'' will be notified by mail of the proposed blasting schedule. However, Section 515(b)(15)(E) of the Act provides that any resident or owner of a structure within one-half mile of the "permit area'' is entitled to a preblast survey. The Office takes these areas to be essentially the same, when viewed over the total permit term of a mining operation, realizing that the actual location of each successive blast within a permit area will necessarily differ from the preceding blast at a given point. Changing "permit area'' as in the proposed rule to "blasting site'' would, therefore, not accord all persons entitled to the preblast survey notice of their rights established under Section 515(b)(15)(E).

However, there are certain types of support facilities used routinely in surface mining activities which do not require the use of blasting. Notification of proposed blasting need not ordinarily be given to persons who reside or own property adjacent to such areas. Thus, Section 816.64(a)(2) was modified in the final rule, to clarify the applicability of the notification requirement with respect to the permit area.

Several commenters also recommended deletion of notice of rights to request a preblasting survey in the copy of the schedule mailed to residences within one-half mile of the permit area, alleging that this is expensive and will generate frivolous survey requests. Another commenter suggested adding notice of the right to request a survey to the newspaper notice. The Office decided to reject both sets of comments. Section 515(b)(15)(E) of the Act provides a right for a preblast survey upon request. To implement that right and to ensure that the public is adequately informed (Section 102(i) of the Act) of its rights, the Office is requiring that notice of these rights be made by mail to the persons involved. Newspaper notice, on the other hand, would duplicate notice by mail and could generate survey requests by persons outside the one-half mile zone.

Alternative 4.

One commenter pointed out that the requirement to publish changes in areas on schedules of blasting would also require renotification of all residents and owners within the area of a right to a preblast survey. Since the purpose of the pre blast survey is to provide baseline data, additional surveys are unnecessary, unless the structures or facilities studied have changed. Section 816.64(c) was revised in the final rules to eliminate requiring information relative to preblast surveys to be included in mailed notices of changes in blasting schedules, when notices previously mailed to the owner or resident have already supplied that information.

Other Comments.

A commenter recommended that the regulations be amended to provide that the blasting schedule be submitted to the regulatory authority. This comment was not adopted, however, because the schedule will have to be retained by the permittee and made available for inspection in order to know when republication is necessary. Of course, if individual States desire such information, such a requirement can be included in their regulations.

Another commenter felt that special notification conditions are necessary in Alaska. Section 708(d) of the Act and 30 CFR 731.13, 736.22(a), 741, allow for the regulations to be modified to fit the special conditions of Alaska. Such modifications are not, however, within the scope of the instant rulemaking.

Section 816.64(a)(3).

A. Several comments were received concerning the provision of the proposed regulations that required renotification by the permittee of its blasting schedule every three months. A review of the comments resulted in consideration of the 3 alternatives listed below; alternative 3 was adopted.

1. Delete the requirement for renotification.

2. Retain the provision as proposed.

3. Retain the requirement for renotification, but lengthen the time period beyond three months.

B. (1) Several commenters recommended deleting this subsection in its entirety, arguing that the Act does not explicitly require renotification of blasting schedules. These commenters alleged that renotification is an unnecessary cost, with one commenter citing $1,800 as a median cost to prepare, copy, publish, and distribute the schedule. Another commenter recommended that the section be changed to provide for an original notification covering the expected life of the mining operation, and to republish and redistribute the schedule only in the event that life of the operation is extended beyond that noted in the original schedule. Section 515(b) (15)(A) of the Act requires the regulatory authority to promulgate regulations that will include provisions: . . . to provide adequate advance-written notice to local governments and residents who might be affected by the use of such explosive, by publication of the planned blasting schedule in a newspaper of general circulation in the locality and by mailing a copy of the proposed blasting schedule to every resident living within one-half mile of the proposed blasting site . . . prior to blasting. ( emphasis added ) There will be persons who will begin to travel or work in or move into the area around permitted operations only after the original notification of the blasting schedule. Therefore, renotification of some frequency is needed so that those persons are given the "adequate advance written notice'' required by the Act. Further, as the comments on the proposed blasting plan portions of the permit regulations (30 CFR 780.13) showed, highly detailed predictions of blasting operations cannot ordinarily be given several years in advance of conducting those operations. Thus, renotification of blasting schedules will be needed on, at least, approximately annual frequencies as detailed information on blasting becomes available to the permittee.

Renotification of the blasting schedule at least every 12 months can reasonably be expected to keep the populace adequately notified and aware of the blasting schedule and sufficiently reduce the expense that would have been needed to comply with the proposed regulations. By lengthening the maximum time period from three to 12 months, small mining operations, where necessary blasting can ordinarily be completed within 12 months, will be spared the expense of renotification of the blasting schedule, unless changes in operations are made during the 12-month period.

Section 816.64(b)(2)(ii) A. Numerous comments were received relative to the provisions of the proposed regulations limiting blasting to periods not exceeding an aggregate of four hours in any one day. A review of the comments resulted in consideration of four alternatives; alternative 1 was adopted by the Office.

1. Retain "aggregate of four hours'' as published in the proposed regulations; 2. Change to "aggregate of eight hours;'' 3. Change to "between Sunrise and Sunset;'' {15186}4. Delete the last sentence of the section, i.e., allow blasting throughout the day, without limitation on the length of the time periods.

B. Numerous commenters objected to the aggregate of four hours as promoting unsafe operations, principally on the theory that blasters would be rushed to meet a certain specific time period, causing mistakes in detonation which would be dangerous. These comments, however, were based on misinterpretation of the regulations, which require only that ". . . such periods shall not exceed an aggregate of four hours in one day .'' (emphasis added) This would allow for blasting at more than one time period in one day, so long as the aggregate of total blasting time does not exceed the maximum of four hours. Thus, there should be no necessity for operations to "rush'' to blast at one particular hour, as personnel engaged in blasting can detonate the round during any one of the scheduled periods in the daily aggregate of four hours. Furthermore, as is explained in Section 861.65(a), blasting may be delayed and conducted at a previously unscheduled time under carefully prescribed conditions, if specified unavoidable hazardous conditions arise, in order to avoid safety hazards to workers.

(2) Many commenters stated that the four-hour limitation would unduly inhibit operations and was not authorized by the Act; several commenters objected that they could not sufficiently predict when blasting would be conducted. Some commenters also stated that the limitation would increase costs, but provided no supporting data. As previously discussed, however, the regulation allows for multiple blasting periods, aggregating to a daily total of four hours, giving a great deal of flexibility to an operator to fashion its own blasting schedule. Because the regulations only specify that detonation must be within the time frame, the operator can do all preparation for blasting during other times. In fact, several commenters stated that if it was clear that several different times aggregating to four hours was permitted, then the four-hour limitation would be acceptable.

Regardless of possible inhibition of operation and costs associated with these limitations, the Office must establish some time limitations on blasting under the Act. Section 515(b)(15)(A) of the Act requires that the person conducting surface mining activities ". . . provide adequate advance written notice to local governments and residents . . . of the planned blasting schedule.'' Thus, some limitation on the frequency of blasting must be imposed, to ensure that predictions are made by the operator for the purpose of including in the schedule "adequate advance written notice.'' Secondly, Section 515(b)(15)(c) of the Act requires that blasting be limited with respect to the "timing and frequency of blasts . . .'' Therefore, limitation on the total duration in which blasting may occur in any one daylight period is appropriate to implement this Section of the Act.

Given that the Act requires establishing limitations on the timing of blasting, the industry must develop the capability of planning its operation so as to be able to predict in advance, to a certain extent, the times in which blasting will occur. As noted above, some commenters indicated that this can be done under the "four-hour aggregate'' system, which is what the Office requires.

(3) Comments that suggested limited blasting only to eight hours per day or "sunrise to sunset'' would not meet the requirements of the Act. These limitations would not provide a schedule with sufficiently specific advance warning to inhabitants of areas around the minesite, persons traveling through these areas, and local governments so as to allow those persons and governments to regulate their daily activities around normal work or business hours when blasting would take place.

V.

Section 816.64(c).

Additions were made to this Section from the proposed regulations, due to comments received and discussed under the preamble to Sections 816.64(a)(2) and 816.64(b)(2)(ii). SECTION 816.65 Use of explosives: Surface blasting requirements.

Section 816.65(a).

(A) A few commenters objected to allowing the regulatory authority to specify time periods for allowable blasting that are more restrictive than sunrise to sunset, while others recommended further restrictions on blasting between 5 p.m. to sunset. Some commenters objected to prohibiting blasting at night, alleging that it may be dangerous to hold undetonated charges overnight. Other comments proposed that the regulatory authority be allowed to grant exemptions for night blasting on a site-specific basis in remote areas; additional comments cited the special conditions in Alaska as an example where restrictions on night blasting are unreasonable. One commenter assumed a conflict between this section and MSHA's proposed blasting regulations. A review of these comments resulted in the Office's consideration of five major alternatives; alternatives 4 and 5 were adopted.

1. Retain the Section as proposed; 2. Allow blasting at night in "remote areas;'' 3. Modify the Section to add further restrictions on blasting between 5:00 p.m. and sunset; 4. Modify Section 816.65(a) to be more specific as to the reasons the regulatory authority may use to specify more restrictive time periods on an ad hoc basis; 5. Modify Section 816.65(a), by adding a provision to allow for blasting at night on loaded charges that cannot be either detonated by sunset or delayed until sunrise of the following day for safety reasons. (This alternative included attaching conditions to the use of night blasting, to ensure that the public is still adequately warned and protected as required by the Act.) (B) Alternatives 3 and 4.

A few commenters objected to allowing the regulatory authority to prohibit or otherwise regulate blasting in time periods in addition to the sunset-to-sunrise restriction. These comments objected to the vagueness of the discretionary power which would have been granted the regulatory authority under the proposed rule. The Office agreed that more specificity is desirable. Accordingly, the regulations have been modified to clarify the conditions under which the regulatory authority has the power to further modify hours for blasting.

The regulatory authority will only be empowered under Paragraph (a) to impose more restrictive blasting time periods for the specific purpose of protecting the public from adverse noise. In some cases, protection against noise may warrant special precautions, particularly because it can be much more severe under certain atmospheric conditions (Ref. 25, p. 404 and Ref. 21, p. 15). The public is adequately protected from other effects of blasting, such as ground vibrations and flyrock, by Sections 816.65(g) and (1). A few commenters recommended that blasting should be further restricted, than in the proposed regulations, between 5:00 p.m. and sunset, because of noise caused by blasting that would occur during those hours when people relax at the end of the day. The Office did not accept this recommendation as it would be redundant. The regulatory authority may specify more restrictive time periods to protect from adverse noise under Section 816.65(a)(1).

(C) Alternative 5.

Several commenters noted that it may be dangerous to hold explosive charges overnight which were loaded with the intention of detonation during the day, but through equipment failure or sudden adverse weather occurrences could not be detonated until after sunset. These comments asserted that, in the next day, the explosives could react to detonation by blowing out and throwing rocks over the area, due to moisture accumulation in the charge holes, or could result in incomplete or no detonation at all. The threat of such contingencies was said to be safety problems to the workers, such as in digging out undetonated explosives. Some of these comments recommended modifying the regulations to allow for blasting at night to prevent these safety problems.

{15187}Although not fully explained by the comments, throwing of rocks could possibly result from leaving undeto nated charges held overnight. Due to the deteriorating effect of moisture in the blast hole on some types of explosives or blasting agents, some of the charged blast holes in a blast may not have the power necessary to fragment surrounding rock as originally planned. Under these circumstances, it is probable that some charged holes would lose their potential power to a greater degree than others, due to having been in the ground for a greater number of hours or being subjected to more moisture. Where charges that retain a considerable portion of their original power were adjacent to more severely weakened charges, a situation could be created that would result in excess rock being thrown in the air. This could be caused by the failure of some weakened charges to move the rock burden in a lateral direction as planned, with the more powerful charges only moving rock in a vertical direction.

As a result, the Office decided that a change in the regulation should be made to allow blasting at night, when it is necessary to prevent creating a hazardous condition, while maintaining controls to prevent abuse of the provision. These controls are imposed to ensure that the public is adequately warned of an emergency blast and that records are made and reported to the regulatory authority to ensure that the provision is not used except in unavoidable hazardous situations.

The Office notes that, while MSHA currently does not prohibit all surface blasting at night, a proposed revision to MSHA's regulations (33 CFR 477. 1308(j)) would create such a blanket prohibition. The Office will, however, ensure that its regulations are closely coordinated with MSHA's final rule and expects that, given the safety problems discussed above, MSHA will appropriately modify its proposed regulation when adopted in final form.

(D) Alternative 2.One commenter proposed that the regulatory authority be allowed to create exemptions for blasting at night, on a site-specific basis, for surface mines in "remote areas.'' This comment was rejected. The Act requires that blasting be appropriately restricted as to times without regard to the density of population in surrounding areas. Indeed, the Act requires protection of even a few persons (i.e., "the public'') in areas located near to the permit area. Furthermore, the use of the "remote area'' concept would be very difficult to enforce, because it would require extensive field investigations to determine the density of population in areas surrounding minesites, often in very difficult terrain, thereby utilizing enormous regulatory authority resources for the benefit of very few mine operations. I11(E) A commenter from Alaska objected to the restriction on nighttime blasting due to portions of that State having up to 5 1/2 months of completely daylight time and winters where daylight is only 2 3 hours a day in areas where coal is actively produced. This was decided to be outside the scope of this national rule-making and should be addressed, if valid, through appropriate special provisions for Alaska under Section 508 of the Act and 30 CFR 731.13, 736.22(a)(1), and/or 741, depending upon whether the State of Alaska seeks to implement its own State program.

(III) Section 816.65(b).

(A) MSHA commented that this section, as proposed, was unclear in two ways. First, unscheduled blasting was to be allowed only in "emergency conditions approved by the regulatory authority.'' The Section did not specify when or how these situations would be approved by the regulatory authority and left the implication that operators would have to contact the regulatory authority, after an emergency arose, to obtain permission to blast at unscheduled times.

The Office agreed with this comment and has reworded the Section to read, "previously approved by the regulatory authority in the mining plan.'' Though 30 CFR 780.13(f) requires that applicants for permits list such situations in the permit application, persons who are responsible for meeting the requirements of Section 816.65(b) could have misinterpreted the method and time of regulatory approval as the section was previously worded.

MSHA's is second concern was that the word emergency, along with the listing of "rain, lightning, other atmospheric conditions,'' was not consistent with MSHA terminology. MSHA considers rain and lightning to be expected and recurring hazardous events, not emergencies. MSHA labels such events as "hazardous situations,'' along with emergencies (totally unexpected events which are also hazardous, e.g., fires). The Office agreed to substitute MSHA's term, hazardous, for emergency, which makes terminology of the two agencies consistent and describes all situations which threaten operator or public safety. The Office has further limited approval of unscheduled blasting to those times of unavoidable hazardous situations, preventing approval of situations which could be created by the operator to justify deviation from the blasting schedule for convenience and not safety's sake.

Adoption of these changes in Section 816.65(b) also required changing the word emergency to unavoidable hazardous in Sections 816.64(b)(2)(v), 816.65(a)(2)(i), and 817.65(b)(2)(i), and adding it at Section 780.13(f), to maintain consistency of terminology throughout affected portions of the regulations.

(B) (1) Several other comments received on proposed Section 816.65(b) suggested that additional requirements be added, that the blasting schedule be eliminated, and asserted possible conflicts with MSHA regulations. Analysis of these comments led to consideration of three alternatives; alternative 1 was adopted.

1. Revise Section 816.65(b), only as per MSHA's comments. 2. Require a report to be submitted to the regulatory authority, within 10 days of any emergency blast.

3. Explain the definition of emergency condition in this section.

(2) Alternative 2.

One commenter recommended that the emergency conditions and reasons for deviating from the blasting schedule be documented and reported to the regulatory authority within 10 days of the occurrence of the blast. The Office believes that the recording requirements of Section 816.68 are adequate to ensure that sufficient information about the blast is developed and maintained for scrutiny by the public and regulatory authority. Under Section 816.68, the permittee must record pertinent information about each blast contemporaneously with blasting and maintain that record for public and regulatory authority inspection. This should be adequate, on a national basis, for regulation of the wide variety of circumstances in which emergencies may occur.

I11That range is distinguishable, however, from the narrow type of circumstances when blasting at night would be authorized in Section 816.65(a). In the latter situation, reports should be filed with the regulatory authority much less frequently, and the regulatory authority needs to more closely scrutinize night blasting because of its high potential for causing adverse noise effects. The decision on Section 816.65(b), of course, will not preclude individual States from requiring the filing of such reports, if their needs require it.

(3) Alternative 3.

Another commenter suggests that the conditions justifying deviation from the schedule be expanded to specifically include "events beyond the operator's control.'' The Office feels that this is adequately provided for by substituting the adjectives unavoidable and T3hazardous to describe those situations which warrant unscheduled blasting.

{15188}(4) Other Comments.

One commenter's objection, that the schedule, stating it is impractical to establish, was rejected. The Act in Section 515(b)(15)(A) requires a blasting schedule.

Another commenter suggested that there are some differences between Section 815.65(b) and MSHA's regulations, 30 CFR 77.1303(uu) and proposed Section 77.1305(g). MSHA's existing and proposed regulations call for suspension of operations and withdrawal to a safe location of all persons upon the approach of an electrical storm. The Office does not believe that these create a conflict with Section 816.65(b), as the withdrawal would constitute justification for deviation from the proposed schedule, if the operator's permit had provided for such conditions under Section 780.13(f). If delay because of storm conditions had not been approved by the regulatory authority in the permit, the operator would have to wait for the next scheduled time period to conduct blasting operations. In no event does Section 816.65(b) allow for blasting during an electrical storm.

III.

Section 816.65(c).

(A) A number of commenters objected to the requirement that warning and all-clear signals be given which are audible at a distance of one-half mile from the blast site. Other commenters felt that this provision is already covered by MSHA regulations, that particular items should be deleted, that additional sections should be added covering specific provisions on safety in the storage and use of explosives, that the signals should be audible "under normal weather conditions'', that some wording was unnecessary, and that the section was inappropriate for the State of Alaska.

The Office's review of these comments led to the consideration of four major alternatives and the adoption of alternative 1.

(1) Do not revise this Section from the proposed rule; (2) Reduce the audible limit to one-quarter mile or less; (3) Delete the requirement for periodic notification and posting of signs; (4) Specify the signal source and signal character.

(B) Alternative 2.

Several commenters recommended that the audible distance requirement for signals be reduced to one-quarter mile or less. Some of these commenters asserted that, to meet the requirement that the signal be audible for a distance of one-half mile, the noise level of the signal would be greater than allowed by MSHA. Although the particular regulation was not specified by the commenters, 30 CFR 70.510(b)(3) of MSHA's regulations lists a table of permissible noise exposure levels as follows: _______________________________________________________________________ Duration per Noise level days (hours) (dBA) 8 90 6 92 4 95 3 97 2 100 11/2 102 1 105 3/4 107 1/2 110 1/4 or less 115 700 (Figure 1) ____________________________________________________________________________ These do not substantiate the commenters' assertion that the requirement for warning signals audible to one-half mile from the blast would require a sound source that would exceed MSHA's allowable noise levels at the mine. First, several warning signal devices can be appropriately positioned at strategic locations within the one-half mile area and the sounding of the several devices coordinated electronically or by some other means. The noise levels from the individual devices would be considerably less than for a single device used to notify the entire one-half mile area. The Office's regulations do not specify that a single signal device has to be audible for one-half mile. Rather it requires that signals that are audible within a range of one-half mile shall be given.

Second, as provided in MSHA's Section 70.510(b)(3), a sound level of 115 dBA is an allowable level for up to 15 minutes per day.

Adequate warning signals under the Office's regulations can be conducted to aggregate less than 15 minutes per day, particularly considering that blasting may only be conducted within a total aggregate of four one-hour periods. Thus, warning and all-clear signals may be divided into eight segments of one minute each, far less than the 15-minute limit imposed by MSHA's regulations. Third, calculations made by the Office and contained in its administrative record indicate that a warning signal sounded at 115 dBA (MSHA's maximum in Table 1) or less can be audible at a distance of one-half mile.

(C) Coverage by MSHA.

Several commenters stated that the provisions of this Section are already adequately addressed under MSHA's regulations. MSHA has only one proposed signal warning regulation (30 USC 77.1308h), and it merely provides that "ample warning shall be given . . .'' However, Section 515(b)(15)(A) of the Act requires that daily notice be given to residents/occupiers in the area that are within one-half mile of the blast site. Therefore, the Office decided not to alter the regulation, because the provisions of this section will fulfill the Act's requirement for daily notification of the public, in a manner that is satisfactory, appears to be most practical, and does not duplicate MSHA's proposed general requirement.

(D) Alternative 4.

A few commenters recommended that additional provisions be added to Section 816.65(b), to specify rules on handling explosives, and that this paragraph be modified to specify the actual signal type and the signal source. The material that was recommended to be inserted is covered in MSHA's rules, 30 CFR Part 77. Addition of those rules would be mere duplication of MSHA, as opposed to the requirements for when signals are to be given and at what distances they must be audible, and would not provide any greater protection to the public or environment. If conditions in particular States require specific signals or signaling devices, these can be adopted in that State's regulations.

(D) Alternative 3.

Several commenters recommended deletion of the provisions for periodic notification or communication of the meaning of signals and maintenance signs. Commenters felt that miners and visitors are warned and instructed when entering the property. That, in itself, would not, however, provide warning instructions for residents within one-half mile, if they are not employees of the mine. Therefore, the comments were not accepted.

(E) Other comments.

(1) One commenter recommended that the section should be changed to "audible, under normal weather conditions, within a range of one-half mile.'' The Office did not feel that this modification would improve the regulations, as the phrase "normal weather conditions'' would be subject to highly variable, and the statute requires adequate warnings without regard to the type of weather conditions. Indeed, severe weather is the time when warnings are most necessary, because of the increased danger of airblast and reduced visibility for persons traveling near the permit area.

(2) A commenter stated that the phrase, "through appropriate instructions,'' should be deleted as unnecessary additional wording. This wording specifies how the information shall be communicated and the Office, therefore, decided it should be retained to ensure that the Act is fully implemented.

(3) Another commenter alleged that there are significant differences between most mining to be covered by this Section and conditions of mining in the State of Alaska. This comment was believed to be outside the scope of this national rule-making and can be more appropriately resolved when a particular permanent regulatory program is approved for Alaska under Subchapter C and D. {15189}(4) Several commenters alleged that the blasting schedule provision is redundant, because audible warnings required prior to a blast under Section 816.65(c) would be sufficient. Audible warnings alone, however, are not sufficient. The Act specifically requires publishing of blasting schedules in advance. Furthermore, audible warnings will not provide adequate advance notice either to persons inside buildings in the area around the minesite (and thus cut off from the signals), or to persons who travel through the blast area between the signal and the blast.

(5) Several comments cited Gustafsson (page 256, ref. 8) on the effects of atmospheric conditions on the propagation of blast noise, as justification for eliminating the four-hour time aggregate. Gustafsson correctly points out that_ ". . . wind direction, wind velocity, air temperature, and air pressure have a very great effect on the propagation of pressure waves. Even the type of weather, for example cloudy or almost clear, should be taken into consideration when estimating the propagation of pressure waves. . . .'' However, the multiple time frames allowed by the "four-hour aggregate'' rule of Section 816.65(b)(2)(ii) and the emergency blasting provisions of Section 816.65(a) and (b) provide a degree of flexibility such that the requirement for a blasting schedule need not be the cause of blasting at times when atmospheric conditions may cause propagation of blast noise. If the blast cannot be detonated during any of the scheduled blasting periods because of adverse atmospheric conditions, the blast can be detonated when necessary in accordance with Section 816.65(a) and (b).

(6) One commenter stated that the "four-hour limit is meaningless,'' asserting that operator will be able to blast for 10 minutes in any hour and thus blast every half-hour throughout the day. The regulations, however, do not allow this to occur. Section 816.64(b)(1) states that "a blasting schedule shall not be so general as to cover all working hours. . . .'' Section 816.64(b)(2)(ii) states that "such periods shall not exceed an aggregate of four hours.'' (Emphasis added.) These sections of the regulations limit blasting operations to not more than four specific hours. Thus, blasting could occur during the hours of 9 a.m. 10 a.m., 11 a.m. 12 p.m., 1 p.m. 2 p.m., 3 p.m. 4 p.m., but not in 10-minute increments of each of the hours 9:00 a.m., 10:00 a.m., 11:00 a.m., 12:00 p.m., 1:00 p.m., 2:00 p.m., 3:00 p.m., 4:00 p.m., 5:00 p.m., 6:00 p.m., 7:00 p.m. To further ensure that this system is not abused and provides for protection against the hypothetical situation raised by commenters, a provision was added to Section 816.64(c) to allow the regulatory authority to require republishing and redistribution of the blasting schedule, if there is a substantial pattern of non-adherence to the original schedule as evidenced by the absence of blasting during scheduled periods.

IV.

Section 816.65(d).

(A) A few commenters pointed out that some confusion could result from the wording of the proposed rules as to the limit of the "blasting area'' to be protected from entry. Objections were also received on the time limit for guarding and on the protection of livestock. Based on these comments, the final rule was reworded to clarify the area to be regulated and to eliminate the requirements of prohibiting access to the area for a specific time prior to the blast. (B) Several commenters stated that use of the term "blasting area'' would result in confusion as to the actual extent of the area to be regulated under this section. The term "blasting area'' was used in proposed Sections 816.65(d) and 817.65(e), to mean the area possibly subject to flyrock from blasting. However, one commenter stated that MSHA presently interprets "blasting area'' to be confined to the blast hole pattern.

Another commenter expressed the fear that the Office's proposed rule would be interpreted to allow unauthorized persons to enter the blast-hole pattern area at any time until 10 minutes prior to detonation of the blast. Such an interpretation is unwarranted and would be unacceptable to both MSHA and the Office. Further, by deleting the words "blasting area'' and substituting "an area possibly subject to flyrock from blasting,'' the confusion of terms will be eliminated.

(C) One of the commenters also pointed out that, where it is necessary to stop traffic during blasting near public roads, the 10-minute minimum control limit will cause extra inconvenience to the traveling public. The Office feels that it is not necessary to specify a particular time limit prior to the blast for which access to the fly rock area should be controlled.

The purpose of the rule is to assure that the public or livestock will not enter an area where they could be endangered by flyrock during blasting and that access to the area after a blast will not be permitted, until an inspection by the mining personnel indicates it is safe to do so. To accomplish this may require that access to the area be regulated more or less than 10 minutes prior to the blast. Thus, if the section were not re-worded, there would be confusion about the area to be guarded and in some instances the public would be subject to unnecessary inconvenience due to the specified time limit of control prior to the blast.

(D) One commenter also objected to the inclusion of livestock in the regulation on the grounds that all States have livestock fencing laws and therefore the inclusion of livestock was redundant. Livestock constitutes "property'' protected by the Act. Fencing may not be successful in all cases, or fences may be too far apart to preclude widespread movement of animals into close proximity of blasting. Therefore, the Office decided not to delete livestock from the section.

Q04 V.

Section 816.65(e).

Although several commenters supported the proposed version of this section, other comments suggested that either it be deleted, or the wording changed to agree with relevant MSHA regulations. Several commenters recommended deletion on the grounds that the guarding of charged holes is already covered by MSHA and that an additional rule covering the same item is merely duplicative. MSHA does, in fact, cover the protection of charged holes under 30 CFR 77.1303(g), which provides: "Areas in which charged holes are awaiting firing shall be guarded or barricaded and posted or flagged against unauthorized entry.'' The Office believes that the MSHA rule is adequate, so that the Office's proposed rule was redundant. MSHA's regulation will apply to surface coal mining operations throughout the active phase of mining. Blasting is not ordinarily conducted at other times in the surface mining of coal, and the flagging/guarding of holes is related solely to worker protection, not those outside the mine-site. Section 816.65 ( f ) _Airblast Standards (A) Numerous comments were received on a variety of aspects of the airblast standard, including recommendations for both higher and lower permissible noise levels, changes in frequency specifications in Hertz (Hz.), and exemption of certain structures from protection by the standards. A review of the comments resulted in the consideration of the following alternatives. Alternatives 10, 11 and 12 have been adopted.

(1) Retain the rules as proposed; (2) Increase the permissible airblast level; {15190}(3) Decrease the permissible airblast noise level standards; (4) Permit a percentage of the blasts to exceed the noise level standards; (5) Delete the airblast noise level standards entirely; I11(6) Change the Hz ( 3dB) in the table in Section 816.65(e)(1) to Hz ( 3dB); (7) Delete the C-weighted noise level standards; (8) Replace the numerical airblast noise level standards with a stemming requirement; (9) Use only one frequency specification, instead of multiple specifications; (10) Delete the reference to the permit area in Section 816.65(e)(1) and allow a waiver from persons leasing structures from the operators; (11) Add a provision enabling the regulatory authority to require monitoring of blasts; (12) In Section 816.65(e)(2) change the upper limit of frequency from 500Hz to 200Hz and specify "Type 1'' sound level meters for C-slow measurements.

II.

Analysis of Comments and Alternatives A.

Introduction.

_MSHA health standards in 30 CFR, Parts 70 and 71, protect only mine workers from hearing loss caused by continuous noise, such as that emitted by trucks, shovels, car shutters, and crushers. However, impulsive noise, such as airblast resulting from the detonation of explosives is not similarly regulated by MSHA. Because impulsive airblast can cause property damage (Ref. 21, pp 2,3,15; Ref. 25, p.400), the Office has adopted standards to prevent damage to structures and to protect the public from noise resulting from airblast.

Alternatives 2, 3, and 5.

Reference 21 was written in 1974 and was based on 26 quarry blasts and an analysis of the results of a great deal of previous work by other researchers. This reference recommended a 136 dB linear peak value (equivalent to the 130 peak measured at six Hz or lower peak response) as a minimum allowable level for airblast, based on damage probabilities. This data was further supported by more recent work. The airblast noise level standards of the regulations are based largely on a special study conducted by the Bureau of Mines (Ref. 22). The time histories of hundreds of cases of ground vibration, airblast, and structural response to ground vibration and airblast were plotted and analyzed. Using the observed structural response to ground vibration and airblast and observed damage to the structures, an appropriate airblast/ground vibration equivalence, consistent with the latest data on structure response, damage, and tolerable levels was derived.

The noise level limitations specified in the table in Section 816.65(e)(1) represent the conclusion of the Bureau of Mines study, the latest state-of-the-art in understanding coal mine blasting airblast on structures and methods of measurement of that airblast. To increase reliability, two independent approaches were used to derive the values specified in the regulation. (1) The first analysis involved determination of the structural response associated with a one-inch-per-second ground vibration. Plots were made of the previously described data organized into four classes: one-story homes, two-story homes, corner responses (structural), and mid-wall responses (non-structural).

The airblast response data were then similarly analyzed, except that the above four categories were each examined for six types of airblast descriptors. The results of this series of comparisons correlated very closely, probably because the natural frequencies of structures +++1 G1 are within a narrow range (Ref. 12, pp. 6&7).

G2 1 As used in Ref. 22, the natural frequency of the structure is that frequency at which the structure tends to vibrate when excited by an impulsive loading such as airblast or ground vibration from blasting.

Based on the first method of analysis, it was decided that the amplitude of mid-wall and corner motions of structures could be limited to levels below those causing damage, by limiting the amplitude of airblast from 135 to 137dB, 2 N when measured on a blast meter (Ref. 20, pp 20 23 and 21, p. 14) that measures the peak amplitude and has a flat frequency response of 0.1 to 200 Hz (135 dBL (0.1Hz), or when the amplitude of airblast is limited to 109 112 dB when measured with a "type 1'' sound-level meter that will hold the peak reading and uses the C-weighting, slow response described in ANSI Standards S1.4 1971 (dBC-slow).

G2 2 As used in Ref. 22, the dB (decibel) is a measurement of sound pressure and is defined as 20 times the logarithm to the base 10 of the ratio of the measured pressure to a reference pressure of 20 micro newtons per square meter.

Limiting airblast to 137 dBL (0.1Hz) would protect structures from structural damage, when the most disadvantageous combination of structure response to ground vibrations and structure response to airblast is considered (Ref. 22). Consequently, the use of 135 dBL (0.1 Hz) provides a slight safety factor to preclude damage to structures. This factor was also needed to try to reduce human annoyance factors from mid-wall structure motions and associated rattling (Ref. 21, pp. 15 and 16). C-weighted-slow responses were similarly analyzed, with the value of 109 dB C-slow recommended as being equivalent to the 135 dBL (0.1 Hz) level. (2) A second independent technique was used to analyze the airblast response data, involving displacement produced strain which is related to cracking in interior walls (Ref. 22, p. 4), according to the following method: Method No. 2: (Displacement-produced strain method) lowest observed damage level 0.016 in maximum wall displacement using lowest natural frequencies compute theoretical associated air blast Method No. 2 was used because displacement, or the distance a particle moves, is not, by itself, a good damage predictor, since displacement is frequency dependent. Thus, both displacement and frequency should be specified. (Peak-particle velocity does not have this disadvantage, because it is not frequency dependent). However, structure walls and corners have definite frequency ranges (Ref. 22, p. 4).

An analysis was performed to determine the airblast levels associated with the lowest damage case in the available data of 0.016 inches maximum wall displacement. For both mid-walls and gross-structure motions (corners), the most strict values were derived by taking the lowest natural frequencies typically encountered, 12 Hz for mid-walls and six Hz for corners. In all cases, the associated airblast level for both one- and two-story homes equaled or exceeded the 135 dBL (0.1Hz) peak linear and 109 dB C-slow, with most values within a few dB of these limits, further indicating that the 135 dBL (0.1 Hz) and 109 dB(C-slow) limits are necessary to protect from structural damage.

(3) The use of C-slow measurements has been recommended in the Committee on Hearing Bioacoustic (CHABA) Working Group 69 report to the EPA. (Ref. 5, pp. V 1 V 5). The Office is not convinced that this method is superior to peak-linear; however, C-slow is included as an alternative, based on CHABA's recommendation, to provide for the use of another class of monitoring instruments which will give equivalent indications of potentially damaging air blast to the other types of instruments allowed under the regulations.

(4) Some commenters suggested lower noise decibel standards, based on arguments that human annoyance is caused at levels of noise below the proposed standards. Some commenters dispute this, arguing that prevention of human annoyance goes beyond the requirements of the Act. The latter commenters felt that the 135 decibel (0.1 Hz or lower) specification was unreasonable, because it provides an additional safety factor (Ref. 22, pp. 3 5) to prevent human annoyance, as compared with the one-inch-per-second peak-particle velocity limitation, and should be raised to 137 decibels.

{15191}A State agency submitted comprehensive testimony on the annoying effects to humans of airblast at coal mine blasting. Two commenters documented the relationship between sonic boom and surface mine airblasts. Based on a large volume of data, the commenters recommended changing the table values of 135dB, 132dB, 130dB and 109dB, to 128dB, 125dB, 123dB and 98dB, respectively. These data lend support to 135dB, rather than 137dB as a reasonable level. Mid-wall motions and associated rattling caused by airblast (Ref. 22, pp. 1 5) cause not only human annoyance, but can also cause minor damage such as falling bric-a-brac and dislodgement of items from shelves. Furthermore, the Act requires preventing harm to public health and safety, which includes prevention of severe annoyance to people (see Section 515(b)(15)).

The two adverse effects from air blast that were emphasized in the argument for lower airblast levels were loss of sleep and a startle effect. The regulations already are believed to alleviate loss-of-sleep problems, by prohibiting night-time blasting, except in the case of a documented safety hazard under Section 816.65(a). Such a safety hazard, where documented to the satisfaction of the regulatory authority, should reasonably take priority over loss of sleep. It will be the responsibility of the regulatory authority to assure that the night blasting waiver provision is not abused. Therefore, the Office decided not to adopt more stringent noise standards in response to the loss-of-sleep comments.

The "startle effect'' cited by a commenter is based on studies of sonic booms, which are similar to airblast from blasting. However, sonic booms are normally unpredicted events. Because of the blasting schedule provision of Section 816.64 and prohibiting of blasting outside normal daylight hours, Section 816.65(a), the public will have reasonable notice of when to expect blasting, thereby alleviating the startle effect. Also, the Office notes that a warning signal is required to alert the public before blasting, Section 816.65(c).

Furthermore, it is important to note that, because the decibel scale is logarithmic, a 7 decibel (db) reduction from the proposed standard amounts to a reduction of about 55 percent in the sound pressure. (For instance, 132dB=1.69 psi, 125dB=.75 psi.) Based on typical airblast levels (Ref. 21, p. 12 and Ref. 19, pp. 12 and 13), this would be a very difficult reduction to achieve as an absolute limitation. Since Sections 816.64 and 816.65(a) already substantially alleviate the two objections of "loss of sleep'' and "startle effect,'' the proposed airblast standards have not been lowered.

(5) Some commenters stated that meeting the one-inch-per-second peak-velocity limitation will automatically control airblast damage. This is not true. In addition to the charge weight per delay and distance from the blast, which do control both airblast noise and ground vibrations, damage from airblast is independently a function of the type of burden being blasted, type and amount of stemming being used (Ref. 25, p. 403), improper or lack of covering of surface detonating cord, and lack of attention to rock structural weaknesses and weather conditions (Ref. 21, p. 15, Ref. 8, p. 220, and Ref. 13, p. 15). Thus, control of ground vibrations alone will not prevent airblast damage, and the specifications of Section 816.65(e) are necessary for limiting airblast.

(6) A few commenters stated that the airblast standards are based merely on preventing crack extensions in walls of structures and, therefore, distort the purposes of the Act. However, Section 515(b)(15) of the Act requires prevention of damage to structures. Propagation of an existing crack is a reasonable definition of damage, and the prevention of such events is not an unreasonable restriction. Of course, airblast can also cause initiation of new cracks, also considered "damage'' by the Office. As discussed above, the airblast standard will also help to reduce human annoyance, independent of structural damage. (7) Without giving reasons, several commenters asserted that the study of Reference 22 cannot be defended. Some commenters (again without a rationale) felt that the airblast standard is inappropriately tied to the one-inch-per-second peak-particle velocity limitation. The study in Reference 22 was based on hundreds of structure response, ground vibration, and airblast time histories. These data were obtained from field studies involving surface mine production blasts and onsite field measurements. The Bureau of Mines has been the nation's leading research organization in the field of blast vibrations for over 20 years. The researcher who conducted the study on which the airblast standard is based is a recognized authority in the field of airblast and ground vibrations. The large volume of data contributing to the study, the reputation of the organization conducting the study, and the qualifications of the investigator lend strong credibility to the study.

None of the commenters stating that the study cannot be defended have given any compelling rebuttal to the study. None of the commenters gave substantial data which would establish that noise levels significantly greater than those to be allowed under the regulations could preclude damage to structures. Rather, they mainly argued that the specified limits cannot be met 100 percent of the time. As explained below, airblast can and should be adequately controlled to meet the regulation without a variability provision.

Further, damage to structures is created through structural vibrations from both ground vibrations and air blast. Through analysis of hundreds of vibration records from production blasts, the Bureau of Mines established a reliable equivalence between the response of a structure to a one-inch-per-second peak-particle velocity and the airblast levels specified in the tables. (Ref. 22, pp. 1 5). The validity of the one-inch-per-second peak-particle velocity ground vibration damage-prevention criterion is established in the preamble discussion of Section 816.65(f).

Therefore, the validity of the air blast table values for preventing damage has been adequately established by correlation between ground vibration-produced damage and air blast noise levels. The inappropriateness of tying the airblast criterion to the one-inch-per-second peak-velocity limitation was only alleged by the commenters, but no justification was offered. Therefore, the Office believes it entirely correct to establish the noise level standards in the manner selected.

(C) Alternative 4.

Several commenters stated that the table standards cannot be met consistently because of variations in rock subjected to blasting and weather conditions. Some commenters recommended that the operator be permitted to exceed the standard 20 percent of the time.

Historically, airblast from coal mining has not been pervasively regulated in this country. Therefore, it has not been necessary for all mine operators to systematically design blasts to limit airblast, except where specific complaints arose. Commenters' requests that the limitation be met only 80 percent of the time appear to be based on the range of airblast occurring under current practice, rather than what the industry is, in fact, capable of achieving. Reference 25, pages 403 to 405, describes blast design techniques such as stemming and proper burden which will reduce air blast to a level meeting the standards. (See also Ref. 21, pp. 3 and 15). The necessity to consider weather conditions in reducing the propagation of airblast is discussed in Reference 25, p. 404; Ref. 3, p. 15, and Ref. 21, p. 15. The Office, therefore, believes that the operator will be able to meet the standard. If adverse weather problems develop, such as a strong wind blowing in the direction of nearby structures from the blast operation or a strong temperature inversion (Ref. 25, p. 404 and Ref. 21, p. 15), it may be necessary to reschedule blasting until adverse conditions subside.

3 I28 G2 3 A temperature inversion is a condition in which the temperature decreases, then increases with altitude, rather than decreasing with altitude, causing sound waves to be refracted back to the earth. (Ref. 25, pp. 404 405) (Knowledge of the existence of a temperature inversion can be obtained from local weather bureaus).

{15192}Further, a standard requiring compliance only 80 percent of the time could subject the public to potentially damaging airblast for 20 percent of all shots. Such a standard would not fulfill the provision of Section 515(b)(15)(C) of the Act, which requires prevention of damage to property outside the permit area by limiting the duration and frequency of blasting. Furthermore, allowance for the standards to be violated 20 percent of the time is particularly inappropraite where, as here, the Office finds that the factors leading to exceed ances are within the indsutry's ability to avoid violation of the standard. Finally, because blasting is a non-continuous, essentially non-regularized activity, a compliance standard allowing for 20 percent of violations of a standard would be virtually impossible to enforce consistently through field surveillance. Such a standard would require very heavy commitment of regulatory authority resources to monitor for unpredicatble periods of time in amassing and analyzing data until sufficient data were obtained to calculate a 20 percent deviation figure.

(D) Alternative 6.

One commenter suggested a specification of ( 3dB) only, rather than ( 3dB) in Section 816.65(f)(1). A second commenter felt that ( 3dB) allows too much tolerance. No rationale or justification was given for the change from ( 3dB) to ( 3dB), and the Office did not adopt the first comment. The ( 3dB) defines the frequency response limit of the measuring instruments and not the accuracy of the measuring system (Ref. 21, pp. 4 and 5). It is not a tolerance allowed to the operator in meeting the standard, but rather an instrument calibration specification.

4 G1 The ( 3dB) was determined to be a proper specification. The rule has not been changed in that regard.

G2 4 The limit of the frequency of a given instrument is that frequency at which the instrument fails to respond to three decibels or more of the actual noise present.

(E) Alternative 7.

Commenters stated that the C-weighted standard is not valid, because it is alleged not to respond to a great deal of low frequency energy associated with blasting. However, Reference 22, pp. 1 5, established the equivalence of the C-weighted standard to the other air blast damage standards, in terms of its effect on structures and use in precluding damage, thereby indicating its utility even in low frequency situations. The Committee on Hearing and Bioacoustics has supported the C-weighted measurements to the EPA (Ref. 5, pp. V 1 V 5). A state agency, in its comments on this section, also presented a proposed C-weighted specification but made no comment as to its validity. Therefore, the Office decided to retain the C-weighted standard.

(F) Alternative 8.

One commenter felt that a stemming requirement should be specified, rather than an airblast limitation, and another commenter supported the Office's proposal not to include a stemming limitation. Stemming is insert material placed in the top of the blast hole above the explosive charge. Proper stemming alone will not control air blast. Proper blast design (Ref. 1, pp. 373 396) and attention to weather conditions (Ref. 21, p. 15, Ref. 25 p. 404) are also important in controlling air blast. Thus, the suggestion to replace the airblast noise levels limitation with a stemming requirement was rejected.

(G) Alternative 9.Some commenters felt that four different frequency specifications would be difficult to enforce and recommended that only one be selected. All of these commenters recommended their own airblast criteria, each based on four frequency response spectra, which is also the basis for the Office's standard. The Office's multiple frequency standard was selected, because a wide variety of air blast monitoring equipment is available with a wide variety of frequency response. Since a reliable comparability of the frequency responses was established in Ref. 22, pp. 1 5, the multiple standard was adopted to avoid unduly limiting the use of various types of monitoring equipment, all of which are capable of reliably detecting damaging levels of airblast. Because the four different frequency specifications amount to essentially the same level of noise control, the Office has decided to retain the four specification standards to allow for the use of a wider variety of testing equipment.

(H) Alternative 10.

Some commenters suggested deleting the limitation on the exemption of property owned by the permittee and exempt from the airblast standard only that property in a permit area. Another commenter suggested deleting this limitation on the assumption that the permittee's property not be leased to any other person. The first suggestion was accepted, because the Office believed it unreasonable to require a person to protect his own property from airblast whether or not it is within the permit area. In response to the second comment, the regulation was modified to allow a person leasing a structure from the permittee to sign a waiver relieving the operator from meeting the airblast limitation, with respect to that structure.

(I) Alternative 11.

The proposed rules on airblast made no provision for requiring airblast monitoring, where violation of the standard is suspected. The ground vibration Section 816.67(c), has such a provision. To enable the regulatory authority to properly enforce the airblast provisions, wording has been added at Section 816.65(e)(4).

(J) Alternative 12.

One commenter correctly stated that, since the major part of sound energy is in frequencies below 200 Hz, specifying a blast meter with at least 500 Hz is unnecessary and would eliminate the use of satisfactory instruments that are presently available. The Office agreed with this analysis and has changed the regulations to reduce the frequency response specification to 200 Hz.

(K) Other Comments.

One commenter felt that the specification in the regulation for the frequency limit of the noise measuring system should be flat or calibrated.

5 N However, the commenter did not provide evidence of a comprehensive data base suggesting that such equivalencies can be routinely made on a national basis. The regulation has not been changed, as requiring a flat response assures that adequate monitoring instruments will be used. Further, use of calibrated systems on a routine basis would cause doubt as to the accuracy of data collection. G2 5 A specification that an instrument's response is flat means that the response to the frequencies within its range is constant to within less than one dB. Calibration attempts to establish an equivalence between an instrument without a flat response and one with a flat response.

Another commenter felt that adverse weather conditions should be used by the regulatory authority to determine extenuating circumstances in any decision on penalties assessed for violation. This suggestion was not accepted. As discussed more fully above, it is the operator's responsibility to take weather conditions into account when firing a blast. The operator should not create a situation damaging to a private structure, regardless of weather conditions, because the operator can delay blasting until after weather returns to normal.

Some commenters correctly stated that three types of sound level meters are described in ANSI SI. 4 1971. As pointed out in Ref. 12, p. 22, a large amount of the energy in airblast and ground vibration is contained in frequencies below 20Hz. This is reflected in the different sound levels specified when using different blast meters. Because Types two and three sound level meters described in SI. 4 1971 have frequency cutoffs at 20Hz and Type one meters have a frequency response down to 10Hz, it is evident that Type two and Type three meters would not give as good an indication of the potential damage as a Type one meter. The final regulations reflect this by requiring that only Type one meters be used for the C-weighted, slow response values.

{15193}VII.

Sections 816.65(f).

A. Substantial comment was received on proposed Section 816.65(g). Most of the comments requested that the 1,000-foot limitation in subsection (1) be reduced to some lower limit, on the theory that this limitation was arbitrary and had no statutory basis. Several commenters also suggested that the 500-foot limitations in subsection (2) (3) be deleted. Several commenters felt the 1,000-foot limit was acceptable, assuming that specific waiver provisions are available. Other commenters argued that the paragraph should be entirely deleted, because other provisions of Section 816.65 assertedly adequately protect the public, making distance limitations unnecessary. A few comments stated that the phrase "other appropriate investigation'' should be deleted, and a few requested that a provision be added that the distances not be decreased if there was a probability that airblast or ground vibration would be increased. A few comments stated that, either the entire section, or the reference to dwellings should be deleted. Several commenters stated that the 1,000-foot limitation would impose unwarranted costs on the industry. Review of the comments indicated that the following alternative should be considered and that alternative 3 should be adopted.

(1) Retain Section 816.65(f), as in proposed Section 816.65(g); (2) Change the distance limitations from 1,000 /500 /500 / to 300 /300 /500 /, or to 3/4 mile /500 /500 (3) Add the term "seismic investigations'' to Section 816.65(f), retain Sections 816.65(f)(1) and 816.65(f)(2) as unchanged and delete 816.65(f)(3).

B.

Analysis of Comments and Alternatives. (1) Legal Authority.

Several commenters stated that the 1,000-foot distance limitation requiring regulatory authority approval for its waiver was arbitrary and lacked statutory authority. This argument has been rejected in the U.S. District Court for the District of Columbia In Re Surface Mining Regulation Litigation 452 F. Supp. 327, 345 346, (1978). The Court held that the Office does have authority to establish a 1,000-foot distance limit on blasting in its regulations under Section 515(b)(15) of the Act, where those regulations do not absolutely prevent mining. Rather, blasting operations may be regulated, if allowed within the specified limits, upon approval of the regulatory authority.

(2) Alternative 2.

A commenter stated that no blasting should be allowed within 3/4 mile of a residence under any conditions, but provided no evidence to justify this position. Therefore, the Office declined to accept it.

Several commenters recommended distance limitations for Section 816.65(f)(1) of less than 1,000 feet. Some comments suggested 500 feet, two recommended 300 feet, one recommended 800 feet, and five simply stated that 1,000 feet was too great a distance. Most of these commenters based their recommendations on the incorrect belief that the Office did not have statutory authority to set such a limit.

Several others stated that blasting is done safely at distances closer than 1,000 feet, and, therefore, should be allowed. The fact that blasting can be done safely at distances less than 1,000 feet from a structure does not justify eliminating the 1,000-foot limitation. Because blasting can adversely impact public property and safety at distances up to 1,000 feet, if not properly controlled, there is a substantial need for close scrutiny by the regulatory authority of blasting operations within this distance.

Flyrock and noise are particular problems caused by blasting within 1,000 feet of dwellings. In Perry County, Kentucky, flyrock from surface mine blasting several hundred feet away severely injured a four-year-old standing in the doorway of his home and damaged three homes and four automobiles. ( Surface Mining Control and Reclamation Act of 1977: Hearings on H.R.2. before the Subcommittee on Energy and Environment of the House Committee on Interior and Insular Affairs, 95th. Congress, First Session, Part II, p. 313 (1977) ("House Hearings''). In Dante, Virginia, a 200-pound rock was thrown over 2,000 feet from the blasting site (House Hearings, Part II, p. 313). The State of Alabama, recognizing the problem of fly-rock and noise, specifies a distance limitation on blasting of 800 feet, within which special precautions must be taken by covering all detonating cord to minimize airblast and posting of guards to protect against flyrock. (House Hearings, SUPRA Part I, p. 138). Cases have been revealed where blocks of rock up to one-half cubic meter have been thrown hundreds of meters. (Gustafsson, Ref. 8, p. 86).

Blasting is also a problem with respect to excesive ground vibrations within 1,000 feet of dwellings. To comply with the scaled distance formula of 60 at 1,000 feet, the maximum charge weight per delay is 278 pounds, as shown in the table in Section 816.65(i)(2). For ammonium nitrate fuel oil at a specific gravity of 0.8 gm/cc, this amounts to a seven-foot charge length placed in a 12-inch diameter blasthole and a 12.5-foot charge length in a nine-inch diameter blast- hole.6 Since single charges of these lengths would be unacceptable (Ref. 1 pp. 388 390) for blasting in a typical surface mine with bench heights of 50 to 100 feet, the operator would have to take alternative action such as monitoring all shots, using a modified scale-distance formula as allowed in Section 816.65(b), using multiple-delay deck charges within the blasthole, or drilling smaller diameter blastholes. To assure compliance with the one-inch-per-second peak-particle velocity limitation in such a close-in situation, it is important that the operator make his contingency plans known to the regulatory authority and have them approved so that compliance can be properly monitored.

G26 Calculations: ANFO specific gravity (density)=0.8 gm/cc gm/cc 62.4=16/cu. ft. (standard conversion factor) r 2 xh=volume of a cylinder. Therefore: 0.8 62.4 0= (.5) 2 (7.1)=278.41b 0.8 62.4 (.375) 2 (12.6)=277.9lb.

In those situations where the operator is not using scaled distances but is monitoring each blast, special precautions are also necessary, such as those described by a commenter. That comment stated that, historically, an operator's charge weights were 400 1,000 pounds. Assuming that 1,000 pounds is a common charge, this would represent charge lengths of 25.5 feet in a 12-inch diameter blasthole and 45.4 feet in a nine-inch blasthole.

7 These would be acceptable charge lengths under many conditions (Ref. 1, pp. 388 395). Additional precautions to meet the one-inch-per-second peak-particle velocity limit may be needed as shown by the considerable variability to be expected from use of the scaled distance formula.

G27 ANFO specific gravity (density)=0.8 gm/cc gm/cc 62.4 (Standard Conversion Factor)=lb./cu.ft. (Standard Conversion Table) r 2 h=volume of a cylinder. Therefore: .8 62.4 (.5) 2 (25.5)=1,000 lb. .8 62.4 (.375) 2 (45.4)=1,000 lb.

Medearis (Ref. 12, p. 44), has plotted predicted peak-particle ground vibration velocity against distance for a 1,000-pound charge. The curve of the plotted data passes through the one-inch-per-second peak-particle velocity line at a distance slightly greater than 600 feet. Because geological conditions can effect the propagation of ground motion, as has been indicated in Gustafsson (Ref. 8, p. 217), some scatter of data around the curve of predicted velocity can be expected, indicating that the one-inch-per-second limit may be exceeded or reached at distances close to 1,000 ft., if blast design is not employed. The 1,000 ft. distance limitation thus provides a safety factor to account for this scatter and to alert the operator that special precautions must be taken to prevent structural damage.

{15194}(3) Waivers.

Several commenters stated that the 1,000 foot distance was acceptable, providing that the regulations specified the written waivers by occupants or owners of any structures within 1,000 feet of the blast site could be used to justify the lesser distances, instead of compliance with the rest of Section 816.65. Such waivers do not assure the regulatory authority that the operator will take the necessary special precautions to protect the public from the danger of flyrock and to protect the structures involved from possible damage caused by excessive ground motion or airblast. Therefore, this suggestion was not accepted.

(4) Redundancy.Other comments stated that the other provisions of the blasting performance standards, such as Sections 816.65(g), 816.65(f), and 816.65(h), adequately protected structures and the public, making the 1,000-foot/500-foot limitations unnecessary. The Office has carefully considered whether Section 816.65(f)(1) (2) are merely redundant to other sections and has concluded that, to the contrary, these provisions are essential to a rational regulatory scheme for blasting. Section 816.65(f) establishes requirements for advance approval by the regulatory authority of particular blasting events by the operator, that paragraphs (c)(g) & (i), which are generally self-executing, do not ordinarily require. This advance approval requirement is important when blasting is conducted in close proximities to the types of structures and facilities involved.

Numerous comments to the Office indicated that, ordinarily, permit applicants cannot be expected to present detailed information on the frequency, quantities, and location of blasting in the appropriate portion of the application (30 CFR 780.13). The Office agreed that it may be impossible to accurately establish this level of detail until shortly before mining operations actually commence in the field. In addition, preblast surveys of structures in the area around the mine will not ordinarily be performed until after a permit is issued, so data on conditions of those structures suggesting the need for special precautions in the course of implementing the blasting performance standards will not be available in the initial stage of the permit process.

The Act, however, requires that mining operations not be conducted until the operator has borne the burden of proving ability to comply with applicable performance standards. (Sections 102, 506(a), 507(b), 508(a), 510(a) (b) of the Act). As the operator will not be able to provide such a demonstration, in detail, during the formal permit application process, it is essential that regulatory authority scrutiny of blasting operations take place at some later point, prior to the conduct of blasting in relatively close proximity to those structures and facilities where the risk of harm is substantial. Thus, Section 816.65(f) is an important alternative to close scrutiny of proposed blasting operations during the permit application review/approval stage.

(5) Basis for regulatory authority approval.

A few comments suggested removing the phrase "other appropriate investigations,'' from the rule, implying that a preblast survey under Section 816.62 is sufficient data for the regulatory authority to authorize a waiver of the distance limits of Section 816.65(f). Preblast surveys will not necessarily provide sufficient data, however, to determine whether the distance limitation should be reduced. First, preblast surveys are not necessarily required to assess existing physical conditions of structures. Survey reports may, but are not required to, specify how the operator intends to blast. Second, seismic or geologic investigations may be necessary or considered appropriate by the regulatory authority to indicate special conditions existing in the area around the blast site warranting special operational precautions. Third, to determine if airblast noise limits will be complied with, it may be necessary to develop information on weather conditions and proposed blasting procedures. All of these are elements, in addition to a preblast survey report, that may be needed by the regulatory authority before approval is granted under Section 816.65(f). Therefore, the phrase "other appropriate investigations'' has not been deleted.

A few commenters suggested that a provision should be added that in no case should the distance be reduced if there was a probability that the ground vibrations or airblast noise would be increased by blasting authorized under Section 816.65(f). Such an addition would be redundant, however, as Paragraphs (c) and (i) already specify the maximum allowable peak-particle velocities and airblast noise levels. Authority to blast under Section 816.65(f) will not change these ground motion and airblast limits provisions and will not allow for less stringent ground motion and airblast limits to be followed. (6) Costs.

Some commenters said that the 1,000-foot distance limitation would impose unwarranted costs on the industry. A few commenters related the additional costs to the cases where land companies lease houses near mines, with provisions that the occupants must vacate within a 30-day notice. These commenters reasoned that, in these cases, the operator or land company would be forced to issue eviction notices to prevent complaints. The Office does not consider this to be a valid argument for eliminating this regulation. First, the commenters did not show that ordinarily structures and facilities within the distance limits will be owned by the operator. Thus, the distance limit is still important for those persons occupying or using structures or facilities not under the control of the operator within the specified limits. Second, to the extent that the commenters are correct (i.e., in order to comply with the blasting performance standards, persons inhabiting structures in close proximity to the permit area must be physically relocated), the regulations still should be retained so that the health and safety of those persons is protected. Third, the Office does not expect that such removal will ordinarily be required, because the industry should be able to obtain approval of the regulatory authority through establishing that blasting within the specified distances can be done in compliance with the peak particle velocity, air blast, and flyrock performance standards.

The remainder of the commenters predict that, because of doubt as to whether a permit to mine closer than 1,000-feet would be granted, operators will encounter difficulty in obtaining financing or will have to pay higher interest rates. This difficulty should be minimized, however, because the specific focus on the blasting performance standards will ordinarily occur after permits are issued and operators are about to start. Because the 1,000-foot limitation is intended as a distance at which the regulatory authority is to ensure compliance with the other provisions of the blast performance standards, the Office does not expect the permission to mine will be difficult to obtain. It is indeed expected that approvals will be granted in many, if not most, cases. Therefore, this should not be a substantial deterrent in obtaining financing for mining operations.

(7) Blasting near deep mines.

Several commenters suggested that Section 816.65(g)(3) in the proposed rules be deleted, as unnecessary in view of the provisions of Section 816.79. The Office agreed that Section 816.65(g)(3) was redundant, given Section 816.79, and has, therefore, deleted the provision.

{15195}(8) Seismic investigations.

The term seismic investigations has been added to Sections 816.65(f) and 816.65(g) in the proposed rules for clarification, since seismic investigations are an acceptable means of proving that an operator can comply with the blasting performance standards within a distance of 1,000 feet, as regards the peak-particle velocity limits of Sections 816.65(i) and 816.65(j). (See preamble to Section 816.67).

VIII.

Section 816(g) (816.65(h) (in proposed rule).

A. In comments on the proposed regulations, several persons felt that fly rock restrictions are unnecessary. Some commenters felt that the restriction on casting flyrock to one-half the distance to the nearest structure illegally preempts operators' property rights. One commenter recommended a variable flyrock distance standard, based on the slope of the terrain around the blasting location. Some commenters suggested a stemming specification, rather than a flyrock restriction. Many commenters suggested the need for major revisions to this section for clarity and to eliminate redundancy. Based on comments, the following alternatives on Section 816.65(g) were considered, and alternative 1 adopted_ 1. Rewrite the section for conciseness and clarity, eliminating the restriction on throwing rock more than half the distance to roads and railroads; 2. Delete or modify the restriction on throwing rock more than half the distance to the nearest structure; 3. Specify blast design requirements, rather than flyrock distance limits; 4. Permit exemptions from the distance provisions; 5. Delete the provision entirely.

B.

Analysis of comments and alternatives.

(1) Introduction.

Flyrock represents a catastrophic potential for harm to the public from blasting. (House Committee Hearings_ supra.

Part II, p. 283). Flyrock falling through the roofs of structures, cited in those hearings, has the potential to cause death and injury, in addition to structural damage.

(2) Alternative 1.

Several commenters felt that portions of Paragraphs (1), (2), and (3) in proposed Section 816.65(h) were redundant. The Office agreed. The Section has been rewritten as one paragraph to enhance its clarity and eliminate unnecessary repetition of the phrase "no flyrock shall be cast'' and the specific types of structures protected by this section.

In response to one commenter's suggestion, the reference to roads and railroads in the "one-half the distance'' limitation has been deleted. If access to these areas is adequately guarded, as is to be required under Section 816.65(d), no danger from fly- rock should occur.

(3) Alternatives 2 and 5.

A commenter's suggestion for a graduated flyrock limitation based on the slope of the terrain surrounding the blast site was not accepted. A property owner needs the same degree of protection, in the form of a buffer zone, regardless of the terrain slope. Since airborne and groundborne flyrock are treated the same in this Section, the "one-half distance'' requirement gives equal and adequate protection to all.

Flyrock is more difficult to predict than other blast effects. Limiting fly- rock casting to within one-half the distance to the nearest occupied structures provides a necessary safety factor for people living at a mine permit perimeter. If a person lives 50 feet from the mine perimeter, and a blast is 1,000 feet from that perimeter, simply stating that the flyrock may not go past the perimeter would provide inadequate protection from both flyrock that initially lands near the perimeter and then rolls towards nearby structures, and from concussion and debris generated by landing flyrock.

Some commenters felt that it is impossible to control flyrock. This is not true. Flyrock controls, using the basic recommendations from Ref. 1, pp. 373 396, are common practices in the industry. (This reference covers, in detail, proper design for blasts.) If the burden is less than 25 times the blasthole diameter, the shot may become violent and excessive, and fly rock can occur. If the stemming distance is less than 0.7 times the burden an imbalance of forces can occur, resulting in excessive flyrock. Where midseams, voids or other zones of weakness occur in the burden, the blast energy will be released violently through these zones, creating concussion and flyrock. Stemming, rather than explosive, should be loaded in these zones to prevent flyrock. If a blast causes flyrock to be thrown closer than one-half the distance to a structure, the operator should be able to solve the problem, by increasing burden and stemming distances and paying close attention to zones of weakness in the burden.

A comment by a vibrations con sultant that uncontrolled flyrock will occasionally occur was not accepted. Using design techniques spelled out in Ref. 1, pp. 382 395, and Ref. 8, pp. 83, 88, the operator can use sufficiently conservative designs to adhere to the provisions of Section 816.65(h). When blasting near residences, it will be incumbent on the blaster to exercise close control over blast design and pay close attention to the rock structure being blasted to reduce flyrock spread.

(4) Alternative 3.

Some commenters suggested that blast design specifications be substituted for flyrock limitations, based on books identifying items of preferred blast design. However, detailed specifications for blast design to limit flyrock in all cases would be an excessive burden to many operators, because of the extreme variation in rock density, competence, and geology encountered on a national basis, and the lack of substantial data to show a high degree of correlation between each variable of blast design and a specific flyrock distance limit. Given this variation and lack of existing data base, the Office feels that it is preferable to specify required results and leave the method of compliance with the standard to the industry, based upon a choice among variables identified above as controlling flyrock.

(5) Alternative 4.

Some commenters suggested that a provision be made for exemptions to the flyrock limitation, but gave no basis for this suggestion. Substantial exemptions to the limitation would present a hazard to the public. The regulatory authority will not be expected to know the specific structural aspects of the rock to be blasted when receiving permit applications, given the final rules' version of Section 780.13, in response to comments. Because the specific sizes and distances of flyrock will not be known, in detail, the regulatory authority would not be able to routinely make the analysis necessary for approval of exemptions. Further, such an exemption would constitute a total variance from this performance standard, contrary to the limit of Office authority provided by Congress. (See In re Surface Mining Litigation, 452 F. Supp. 327, 338 339 (D.D.C. 1978)).

Other Comments.

(1) One commenter felt the rock traveling along the ground should not be considered flyrock. Since rolling rock can be as hazardous as rock falling upon persons or structures, the provision for rock traveling along the ground was retained.

(2) On the question of pre-emption of the operator's rights, the Act does not allow a person conducting mining to operate within the confines of the permit area so as to cause damage or injury to persons in nearby areas. Sections 102 and 515(b)(15), of the Act. (3) A commenter suggested changing "area of regulated access'' to "safety perimeter.'' This was not adopted, because "area of regulated access'' is a more specific term as it is tied to specification of "access areas'' in Section 816.65(d).

IX.

Section 816.65(h) (Section 816.65(i) in the proposed rules).

{15196}A comment was received recommending deletion of Section 816.65(i) from the regulations as unnecessary, alleging that "actual disruption and fracturing of the rock only takes place very close to a blasthole.'' This is certainly not true in the case of flyrock, which is documented in the legislative history, as described in the preamble to Section 816.65(f). Excessive flyrock could change the course of a small stream by creating barriers to the original flow of water in the stream and by initiation of rock slides in unstable pit slopes adjacent to streams. Moreover, the text of Section 816.65(i) comes directly from Section 515(b)(15)(C) of the Act, and clearly reflects the intent of Congress.

X.

Section 816.65(i), (Section 816.65(j) in proposed rule) Peak-Particle Velocity Limits.

A. A large number of commenters objected to the one-inch-per-second limit for peak-particle velocity of ground motion. The majority of these comments recommended that the limit be placed at two inches per second, although others recommended levels as low as 0.2 inch per second. Other comments inddicated that the proposed rule was ambiguous as to how compliance with the particle velocity standard was to be measured in the field. Some commenters recommended that this section be revised to specify the conditions under which the regulatory authority would monitor ground motion and the equipment to be used. Study of the comments received led to the consideration of the following alternatives: (1) Retain this section as proposed without change; (2) Specify that the maximum peak-particle velocity shall be as measured in any of three mutually perpendicular directions, or specify that the maximum peak-particle velocity is the maximum of resultant of three components which are measured in three mutually perpendicular directions; 8 I28 G2 8 A component is a velocity measurement taken on a pre-determined orientation. The three common components are vertical (v), taken in true vertical orientation; radial (r), taken on the line from the blast to the measurement point; and transverse (t), taken on the horizontal line perpendicular to (r). The resultant is the vector sum of v, r, and t, and is equal to v 2 r 2 t 2 .

(3) Retain the limit of one-inch-per second peak-particle velocity vs. specifying a limit of up to two-inches-per-second peak-particle velocity vs. a limit as low as 0.2 inches per second; (4) Eliminate any specific maximum peak-particle velocity and use an equivalent scaled distance (explosive weight/delay vs. distance to structure) only.

(5) Replace the maximum peak-particle velocity standard with a "structural response'' criterion; and (6) Require the regulatory authority to monitor blasts at a mine without notifying the mine, to use certain specified monitoring equipment, and to require that the operator use trained monitoring personnel versus not providing for such requirements on monitoring.

After consideration of these alternatives, the Office decided to retain the one-inch-per-second peak-particle velocity, specify that this limitation is to be measured in any of three mutually perpendicular directions, and to reject other alternatives.

B.

Analysis of Comments and Alternatives.

(1) Some of the comments received reflected confusion as to the fundamental purpose of this section. These commenters appeared to criticize the one-inch-per-second standard on the theory that the adoption of this standard is an attempt to protect against not only property damages caused by blast ground vibrations, but also against causing any annoyance to people by emotional distress.

As later discussion will explain, the one-inch-per-second standard is based principally on protecting property from damage, although it should also reduce the level of human emotional distress caused by ground vibrations. Bulletin 656 (Ref. 14, pg. 28), based on the Salmon nuclear event, states that an estimated 35 percent of all families will complain when exposed to ground vibrations of two-inches-per-second, and 18 percent will complain at one-inch-per-second. Although frequencies and durations for nuclear blasts are different than for conventional blasts, some similar complaint reduction should be expected in coal mining. Therefore, the standard being adopted is anticipated to reduce emotional distress somewhat, although not completely prevent it.

(2) Alternative 2 _One commenter approved of selecting the "resultant'' form of measurement of peak-particle velocity for ground vibration. As the Office does not intend that the resultant method of measuring the minimum peak-particle velocity be required, Section 816.65(i) was modified to clarify the method of measurement.

The Office has decided that the resultant method should not be used, principally because that method has not been used in collection and analysis of the data in the literature upon which peak-particle velocity standards for mine blasting have been based. All peak-particle velocity data presented in Bureau of Mines Bulletin 656, (Ref. 14, pp. 93 103), was measured as the maximum in any of three mutually perpendicular directions. Therefore, most of the work correlating peak-particle velocity from blasting in mining with structural damage has been done with the velocity determined by measuring the greatest velocity in any of three mutually perpendicular directions, without use of the resultant method.

Investigators working on a relationship between blasting ground vibrations and structural damage continue to determine maximum recommended peak-particle velocity as that measured from any of three mutually perpendicular directions (Ref. 19, pp. 12 13). The historical data pool on ground vibrations and related damage is all based on measurements taken in three mutually perpendicular directions, as opposed to vector sum measurements. Therefore, the three-component system is the only one on which a vibration regulation can logically be based. (3) Alternative 3 _The Office received a wide range of comments as to the level at which the peak-particle velocity standard should be set. Many commenters argued for a level above one-inch-per-second, most of these recommending two-inches-per-second, which was the prevailing industry standard prior to promulgation of the Office's interim regulations in December, 1977. Some commenters urged that the standard be set below one-inch-per-second, arguing that structural damage and/or emotional distress cannot be eliminated, unless peak-particle velocity is reduced to a level as low as 0.2 inch per second.

(a) Some commenters suggested that the two-inch-per-second standard be adopted, alleging that an operator would subject blasting personnel to a great hazard with the one-inch-per-second standard because blasting would have to be conducted more often in order to break up the same amount of overburden. Analysis of this claim does not reveal that it is substantial.

The primary method for reducing ground motion from mine blasting is to reduce the charge weight of explosives per delay (Ref. 7 at 93; Ref. 14, p. 73; Ref. 13, pp. 8 9). In most instances, the same amount of rock can be broken in a single blast by increasing the number of delays used in a round of blasting. Commercial delays, in conjunction with sequential timers, provide between 100 and 200 delay intervals per blast round. (Ref. 17, pp. 1 2). Readily available sales literature indicates that cap manufacturers market 20 different delay periods. Furthermore, detonating cord delay-connectors can be used in series to provide an essentially unlimited number of delay periods per blast. Delay blasting switches (sequential timers) can be used to increase the number of delay periods available when using electric controls (Ref. 12, p. 9).

{15197}A few commenters alleged, however, that increasing the number of delays requires reducing drill patterns, thereby reducing the size of individual blasts and requiring more total number of blasts. Ref. 1, pp. 373 397, however, makes no provision for needing to reduce blast patterns because of an increased number of delays. (See also, Ref. 7 at 93 97 and Ref. 12 and 17, supra. Moreover, the extent that the commenter's assertion might be true, the Act requires precluding damage from ground vibrations.

One commenter also stated, without providing demonstration, that by increasing the number of delays, there is an increased chance of propagation between charges which could lead to damage at closely adjacent buildings. (Propagation is the initiation of a charge by means of an earthborne or airborne shock wave radiating from a nearby detonation.) The blasting agents used in surface mining today are, however, very insensitive to accidental initiation and not subject to charge-to-charge propagation in surface blast designs. (See, e.g., Ref. 7 at 95).

(b) Some commenters that recommend the two-inch-per-second level relied on technical literature or their own experiences to argue that a two-inch-per-second standard is "adequate'' for protection of structures against blast damage. However, none of the commenters who cited their own experiences submitted detailed data showing comparisons between damage and peak-particle velocity from blasting in representative sets of mining blasting situations. Without those data, the Office could not evaluate the claims of those commenters who cited personal experiences, which in any event, appear contrary to the weight of data available in the relevant literature. Technical literature cited by commenters urging the two-inch-per-second standard was primarily Bulletin 656 (ref. 14), Medearis (ref. 12) and Laadegard-Pederson (ref. 10). Bulletin 656, however, states that the two-inch-per-second standard will protect structures from damage only 95 percent of the time. (Ref. 14, p. 73). This is not an adequate standard, because the Section 515(b)(15)(C) of the Act requires prevention of damages. Medearis does not support the two-inch-per-second criterion, but a complex structural response criterion, discussed later. Ref. 10 is a review of various other papers and presents no new data.

One other commenter recommended eight additional publications for study of the peak-particle velocity limitation. Four of these involved only nuclear explosion data, not coal mining, and are not sufficient for establishment of a coal mining standards on a national basis.

The fifth article cited by the commenter was Bulletin 656, (ref. 14) which has already been discussed. The sixth was Bulletin 442, the data from which form part of the analysis in Bulletin 656. The other two suggestions were references 23 and six, both of which are addressed elsewhere and which support the one-inch-per-second standard.

Another commenter suggested that Wiss and Nicholls, ASCE, 1974, supports a two-inch-per-second standard. However, this publication concerns a very limited test, performed with only a few blasts near one house in a hard-rock mining district, and thus is not a sufficiently comprehensive piece of work on which to base a national surface coal mine blasting standard, because of the limited scope of the study and the difference in rock type; i.e., hard rock versus the soft sedimentary rocks associated with coal mining.

Another commenter suggested using Bureau of Mines RI 8168, by Siskind, Stachura and Radcliffe. However, this publication does not deal with structural damage criteria of any type from ground vibration.

(c) When published in 1971, Bulletin 656 was the most comprehensive and best information available on the peak-particle velocity limit. Bulletin 656 recognized (at p. 73) that the probability of damage for a two-inch-per-second vibration would be about five percent. Commenters pointed out that this probability estimate was based on four instances ("points'') where damage could be shown at levels below two-inches-per-second and that these points had the greatest standard deviations.

However, none of the literature cited by the commenters established that no damage will occur at the two-inch-per-second level. Medearis (ref. 12) feels that peak-particle velocity in itself is not a good criterion, although he is the only published authority in our records who takes this specific position. Further, on page 87 of Ref. 12, Meaderis states that his criterion would be more strict than current practice with regard to one-story structures.

Another commenter said that repeated blasting will not cause fatigue damage. The Office has never contended that this was a factor. The damage from repeated vibration discussed in the preamble to the proposed final rules refers to induced settling through compaction of material on which a house is built. Vibration is a standard civil engineering technique for compaction of material. Vibration damage data typically are of a single event type and thus do not consider accumulated effects from multiple blasts. One of these effects could be induced settlement. This is a contributing factor, although not a major one to lowering the limitation from two- to one-inch-per-second, i.e., several small vibrations may do as much damage as one larger one.

(d) One of the commenters who criticized the one-inch-per-second standard recognized that the two-inch-per-second standard is not really adequate to preclude damage. A careful review of the technical literature, as a whole, shows that the one-inch-per-second limit is what is necessary to preclude damage to buildings from blasting. The best available information clearly shows that damage to property may result from blasting vibrations below two-inches-per-second. Indeed, this literature recognizes that even a limit of one-inch-per-second may not absolutely protect structures from minor damage.

Integration of data from Dvorak (Ref. 6) yields 32 points of damage below two-inches-per-second. Gustafsson (Ref. 8. pp. 207 210), using information developed from over 100,000 blasts, recommended a safe level for peak-particle velocity down to 0.7 in-per-second, depending on geologic conditions, and a threshold of damage as low as 1.2 inch-per-second. This is a very impressive volume of actual blast data, and, by its very number, encompasses a wide variety of conditions similar to that present in coal mining across the U.S. Tynan (Ref. 23. p. 19) recommends a peak-particle velocity of 0.75 inch-per-second. These sources thus indicate that a particle velocity specification below two-inch-per-second is necessary in order to protect the majority of structures from damage, and that one-inch-per-second is a reasonable criterion.

(e) Some commenters alleged that the use of the one-inch-per-second limit would be burdensome on operators. Costs will probably be increased, in some cases, because of additional delays required and a small amount of additional loading time. Based on a comparison of use of a scaled-distance formula of 50 (to achieve two-inch-per-second) to use of a scaled-distance formula of 60 (to achieve one-inch-per-second), the charge weight per delay will have to be reduced about 30 percent.9 I28 G29 Calculated by comparing the two scaled distance equations: SD = distance/Charge weight.

Example: Calculation comparing scaled distances of 50 to 60 using an absolute distance of 1,000 feet.

60 = 1,000/ W 50 = 1,000/ W W = 1,000/60 W = 1,000/50 W = 16.667 W = 20 W = 278 lb/delay W = 400 lb/delay 278/400 = 70% If an operator is currently blasting at or near two-inches-per-second, he would have to use approximately 40 percent more delay intervals to achieve the one-inch-per-second based on use of the scaled-distance data in Ref. 14, p. 17. Delay intervals, however, are not a major component of the total costs associated with blasting.

10 G1 These additional costs will, however, be offset by reduced damage to structures and reduced human annoyance. Further, some additional cost is not a valid reason for allowing for blasting with a significantly greater probability of structural damage and human distress, since Section 515(b)(15) of the Act requires that blasting be conducted so as to "prevent'' damage and injury. Moreover, no commenter indicated that surface mining would have to cease in any locations because of increased cost associated with the Office's blasting regulations.

G210 No additional detonating cord would be required to meet the one-inch-per-second standard since the hook-up of explosives would be the same. Some additional delays would be interposed on the surface, but these are less than $1.00 each. In the case where the operator is already using in-hole delays, no additional delays would be needed, only a wider variety. No additional loading time would be required because the same powder loads would be used. There might be a slight insignificant increase in time due to delay pattern design, care in proper loading, etc., If an operator chose to load different delayed charges within a bore hole to reduce the charge weight per delay, this would take a little extra time. The increased time, even with an extremely complex blast, should amount to less than 5 percent; increased cost of materials (delays, cord, etc.) would be almost nil.

{15198}One commenter complained that a large coal company had recently purchased a new drill to acquire capability of drilling smaller holes to meet the one-inch-per-second standard and the entire cost of $250,000 for the drill was an expense in imposing this standard. However, that drill will replace drilling time for older, larger drills and thus the older drills will last longer. Also, the company will have more operational flexibility, by the ability to drill more types of holes. Moreover, there was no way for the Office to calculate accurately how much the drill purchase cost the company in the long run. When lower maintenance (resulting from a newer drill), increased operational flexibility (resulting from an extra drill), fewer complaints and damages (resulting from lower ground vibrations), and better fragmentation (resulting from smaller holes with closer spacings) are considered, the company could even conceivably have saved money by making this purchase. (See, e.g., Ref. 7 at 95 97.) (f) A few commenters recommended lowering the allowable vibration level to below 1 inch/second. In most of these comments, reliance was put on information developed by a State agency and the recommendations contained in Appendix C of the Committee on Bioacoustics and Biomechanics Report (Ref. 5). As was pointed out in comments by an industry commenter, Appendix C was not an actual recommendation made by the CHABA working group, but was included as background information. The material quoted in Appendix C of the report was a summary of the 1976 draft standard, International Standards Organization, Technical Committee 108, Standards Committee 2, Working Group 3. The actual recommendation of the CHABA report was that since structural damage had been observed to levels as low as one-inch-per-second, even that level should be regarded as one of potentially adverse exposure.

(g) A few comments stated that the one-inch-per-second standard was arbitrary or discriminatory against coal mining as compared to other methods of mining. The above material demonstrates that the standard is not arbitrary. Nor is it unduly discriminatory, since the Act requires establishing a standard to prevent property damage and injury from surface coal mine blasting. (4) Alternative 4, Use of Scaled-Distance Formula Only.

One commenter proposed that the ground vibration criterion be eliminated completely, appearing to recommend that all reliance be placed on explosive charge weights and distance formula. Although charge weight-distance formula is one method of protecting structures from ground vibrations (Ref. 14, pp. 70 74 and Ref. 13, pp. 8 9), use of seismographs to predict adequate charge weights is also acceptable. Section 816.67(b) provides that a different charge weight-distance formula can be used, if it can be shown that the maximum peak-particle velocity is not being exceeded. Thus, the Office decided not to accept this comment.

(5) One commenter objected to the provision in Section 816.65(i) that the maximum allowed peak-particle velocity is to be lowered below one-inch-per-second, if required by population density, age of structures, geology, hydrology, or frequency of blasts. The commenter did not feel that a relationship between those elements and ground vibration had been demonstrated.

Gustafsson (Ref. 8, p. 208) found that older structures cannot withstand ground vibrations as well as newer structures. Some evidence does exist that the frequency of blasting does have an effect on structures (Ref. 8, p. 209). Density of population may require a lowering of the ground vibration limitation because of the possibility of increased human distress. Ref. 14, p. 28, shows that the percentage of persons affected by distress is a function of the level of ground vibrations. In high density population areas, a larger number of persons will be distressed, since the number of persons affected is determined by multiplying the percentage of persons expected to be affected by the number of persons in a given area.

In some cases, geologic structure may cause vibrations to propagate more efficiently through the ground and cause more complaints or damage than normal. With regard to effects on hydrology and water supplies, it is clear that blasting can adversely affect ground waters by rock fracturing. (Ref. 7, at p. 2; Ref. 26 at p. 25; Ref. 27, Vol. 1, at p. 120). The regulatory authority, therefore, needs to be provided with authority to specify a lower peak-particle velocity, where use of one-inch-per-second is insufficient.

(6) One commenter objected to the one-inch-per-second standard, saying that mine-caused blasting damage is due to poor enforcement of the two-inch standard, rather than to actual ground vibration levels at two-inch-per-second. The data cited in this discussion, particularly Dvorak (Ref. 6) Gustafsson (Ref. 8) and Tynan (Ref. 23) show, however, that because damage and distress can occur below two-inches-per-second, one-inch-per-second is needed.

(7) Alternative 5.

The Office received a number of comments which objected to the adoption of a peak-particle velocity standard which is based upon the assumption that all structures respond in the same manner to a given ground vibration, as opposed to a standard which is derived from analyses leading to a "structural response criterion.'' These comments urged the latter criterion be used, based on the work of Medearis (Ref. 12) to determine allowable maximum vibration levels.

Medearis' work involves the determination of how a structure will respond to a ground vibration. This response will vary with the frequency of the ground vibrations, the height of a building, the type of ground on which the structure is built, and the type of construction and age of the structure.

Medearis' system requires that the natural frequency of structures be determined by test blasting, along with spectral response curves showing the response of the structure when excited by different frequencies and amplitudes of ground vibrations. The predominant frequencies of the ground vibration, which will vary with the distance from the blast, must also be determined.

It is important to note, too, the Medearis' studies were not performed at actual blast sites. Medearis' studies involved records of 74 blasts provided by Vibra-Tech Engineers (Ref. 12, p. 20) and simulated structural vibrations induced by "slamming doors or bumping appropriate structural components.'' (Ref. 12, p. 4). The structures studied were not those involved in the blasts. His simulated vibrations are not truly representative of blasting events because they excite only selected portions of the structure whereas blast vibrations excite the entire structure. To fully develop the Medearis' system, actual field blasts with associated ground vibration and structural vibration measurements are needed.

{15199}As Medearis states (Ref. 12, p. 87) this technique is based on a limited amount of data and requires further research. In contrast, the one-inch-per-second criterion used by the Office is based on a large volume of published data (ref. 6, 8, and 17) and Bureau of Mines unpublished data which correlate damage directly with ground vibration data, and do not take structural response into account.

Further, some commenters indicated that computer analysis is necessary for using the structural response system in each particular situation, making this a cumbersome and costly procedure, in comparison to the peak-particle velocity limitation, which uses the scaled distance formula or seismographic readings for implementation and compliance purposes. Moreover, given that detailed blasting plans cannot be provided at the permit application stage, there would be no necessary point in the regulatory process where the regulatory authority would have time to conduct an in-depth review of the computer analysis results.

The Office, instead, has decided to use a system involving the alternatives of scaled-distance or seismographic readings, which has been widely used throughout the industry for many years and can continue to be applied under the regulations without the necessity of Medearis' system for gathering site-specific structural data and engaging in computer modeling.

(7) Alternative 6.

Finally, it was also argued that the Section should be amended to provide that the regulatory authority should not notify the mine when ground vibrations are being monitored, that the regulatory authority use only certain equipment and trained personnel, and that the latest equipment should be required for use by well-trained personnel. The Office, however, prefers to leave these enforcement particulars to the regulatory authority in individual cases, based on a case-by-case use of the best testing methodologies and whether notice to the operator may be needed. It was not felt that further modification of this paragraph was warranted.

XI.

Section 816.65(j) (Section 816.65(k) in proposed rules).

(A) Several commenters requested that this provision be modified to afford additional relief from the one-inch-per-second peak-particle velocity limitation at certain structures. Several commenters suggested allowing for waiver of the peak-particle velocity limits at any location under control of the operator or at any property of any other person willing to grant a waiver of the peak-particle velocity limit. Section 515(b)(15)(C), of the Act however, requires that blasting be limited to preclude dangers to underground mines and to surface or underground waters. Thus, allowing for waiver of the peak-particle velocity merely at a particular location would not satisfy the requirements of the Act (See Refs. 26,27), because: 1. An underground mine might be located at or under the surface location of the person agreeing to the waiver, and 2. A spring or stream used by downstream or downgradient persons might pass through or under location of a person agreeing to the waiver for structures on adjacent property overlying surface or groundwaters.

Therefore, the Office decided it could not authorize waivers of the maximum peak-particle velocity limit, without preserving restrictions to protect underground mines and surface and ground waters. As a result, any waivers must be appropriately based on pre-conditions, as specified in Section 816.65(i).

B. Some commenters felt that an operator should not be required to protect his or her own structure from vibrations merely because the structure was leased to another party. If the requirement protecting a lessee were dropped completely, a lessee of the property owned by the operator would lose the right under the Act to protection from discomfort and damage from ground vibrations caused by blasting. Thus, the waiver provision in the final rule was adopted to protect the lessee's rights and still permit the operator to seek relief from the basic requirement of the regulation.

C. Some commenters felt that a structure owned by the operator, even though it is off the permit area, should be exempt from the one-inch-per-second limitation. The Office agrees that the location of the property with respect to the permit area should not be a determinant in authorizing waivers to the permittee. The final rule reflects this.

D. Several commenters felt that the one-inch-per-second limitation should be subject to waiver by a private homeowner or lessee thereof, in addition to structures owned by the permittee. Allowance for these types of waivers, however, can easily subject homeowners and their lessees to undue coercion by the mine operator. Additionally, homeowners may waive rights to protection of their property without realizing the significance of this action. The average lay person is not likely to have adequate technical knowledge for intelligent selection of an alternative peak-particle velocity ground vibration level under a waiver. In comparison, the permittee should have employed competent experts to conduct blasting and upon whom the permittee can rely for advice in deciding whether to use the waiver of the one-inch-per-second limit. Thus, the Office feels that a provision for a waiver from private homeowners or their lessees, other than the permittee, is unjustified.

XI.

Section 816.65(k) and (l) (Sections 816.65(1), (m) of proposed rules).

A. Several comments were received on the use of a scaled-distance formula of 60 as an acceptable means of compliance with the one-inch-per-second peak-particle velocity limitation of Section 816.65(i). As a result of the comments, the following alternatives were considered, and alternative 1 was adopted.

(1) Retain the text of the proposed rules; (2) Reduce the scaled distance equation to 50; (3) Use a scaled distance greater than 60.

B. (1) Scaled distance is an expression which relates the absolute distance from a blast to a structure to the square root of the charge weight of explosive per delay. Although vibration data tend to have considerable scatter, equivalent scaled distances tend to give similar vibrations. The scaled distance equation is as follows: SD = R/ W Where R is the distance from the blast to the structure in feet, and W is the charge weight per delay. The following examples will illustrate this. Given distances of 1,000 feet and 5,000 feet, what is the maximum charge weight per delay that can be used in complying with a scaled distance of 60? A scaled distance of 50? 1000 ft.

5000 ft.

60 = 1000/ W 60 = 5000/ W SD = 60 W = 1000/60 W = 5000/60 W = 16.667 W = 83.333 W = 278 lb W = 6944 lb SD = 50 50 = 1000/ W 50 = 5000/ W W = 20 W = 100 W = 400 lb W = 10,000 lb (2) Analysis of Comments and Alternatives (a) Alternative 2. Several commenters stated that a scaled distance of 50 should be adopted, based either on ref. 14 or on the commenter's practices. Ref. 14 discussed use of 50 as a basis for meeting a peak-particle velocity standard of two-inches-per-second, and it was the information in that bulletin that set the established practice.

{15200}Because the particle velocity limitation is being reduced to one-inch-per-second, a higher scaled distance was required for compliance with this lower limitation. The scaled distance of 60 was derived from the combined velocity data, p. 71, Ref. 14, The Office recognizes that the 60 scaled distance is an empirically derived number with a built-in safety factor, and therefore, permits the operator to seek relief by deriving a site-specific scaled distance factor, based on seismographic data from a particular blast site, subject to approval by the regulatory authority. (Section 816.67(b)).

(b) A few commenters stated that a scaled distance of 50 will keep vibrations in the 0.5 inch per second range. The data on page 71 of ref. 14 refute this assertion. In any event, if the operator has a property at which the scaled distance of 60 is unduly restrictive, he may seek relief under Section 816.67(b), by use of site-specific seismograph data.

(c) Several commenters argued that the scaled distance of 60, when compared with the scaled distance of 50, results in a reduction by 30 percent of the weight of explosives to be detonated at one time. This is true, but the fact remains that the scaled distance of 60 is necessary to keep vibrations below one-inch-per-second, unless the operator seeks relief under Section 816.67(b) or meets the higher scaled distance by emloying more delays in the blast.

(d) Alternative 3. A State environmental agency recommended that the scaled distance should be 100 for compatibility with one inch per second, but provided no detailed data to substantiate this. The combined data on page 71 of ref. 14, furthermore, based on recordings of 159 blasts in 24 operations, refutes this contention.

(e) Other comments.

(1) A commenter stated that no scaled distance is adequate to protect against a specific level of ground vibrations because of variations in blasting-cap firing times. (Ref. 23, pp. 17, 21, 24 and 27). Manufacturers and the industry have been aware of this firing time scatter since the development of delay caps. However, the data enumerated above, from which the 60 scaled distance was derived, are empirical data obtained from blasts using detonators with assumed scatter in firing times. Thus the cap scatter is automatically incorporated and accounted for by the results of the data analysis supporting the 60 scaled distance.

(2) One commenter recommended that the specification that the scaled distance be determined by reference to the distance to the nearest structure should be clarified, to b