# Chapter 27: Record Keeping

Every blast is the result of a large amount of planning and implementation that includes the steps outlined in table 27.1. Each of these steps is normally regulated by government agencies interested in public or workforce safety. In tandem with the regulators are the insurance companies interested in minimizing their exposure. The common interest of all these entities is record keeping.

## Blast Planning Steps

| Step | Description |
|------|-------------|
| 1 | Project bidding |
| 2 | Permitting |
| 3 | Public Relations |
| 4 | Transportation and Storage |
| 5 | Safe storage |
| 6 | Safe transportation |
| 7 | Blast designing |
| 8 | Drilling |
| 9 | Loading |
| 10 | Blast initiation |

*Table 27.1 – Blast planning steps.*

Record keeping in today's world is necessary to track explosives from manufacturer to consumption. Up until blast initiation, the records will focus on: (1) planning, (2) safety, (3) security, and (4) implementation. After initiation the emphasis shifts to documenting results and compliance with regulatory vibration limits and blast plan conditions. Good blast record keeping provides the benefits listed in table 27.2.

## Good Record Keeping Benefits

| Benefit |
|---------|
| Liability protection |
| Verification of company and blaster professionalism |
| Post blast evaluation |
| Proof of compliance with regulations |
| A history of the blasting related activities |

*Table 27.2 – Good record keeping benefits.*

All preblast conditions, field loading practices and blast monitoring, whether or not they are subject to regulations, must always be fully documented. Common sense dictates the need for a complete record-keeping program because blasting falls under strict liability laws as discussed in chapter 30. The risk of litigation is very real, and this risk alone should convince blasters that legible, accurate and complete records are essential. Methods of managing risk to control liability are discussed in chapter 29. In the event of claims or litigation, these records are certain to be called into evidence and should be absolutely unassailable.

After a blast, the blaster should review the blast and monitoring results to evaluate blast design, product performance and blast crew performance. For example, a poor blast, while well designed on paper, could be the result of poor loading practices as evidenced by a video recording, thus indicating the need to retrain or refocus the blasting crew. Another example is when a mine operator perceives the pit floor to be rising, assumes that the blasting contractor did something wrong, and wants a cost adjustment. However, examination of the drill logs, blast logs, and face profiles confirms an upheld fold.

From a business perspective the blast records may be an element that is reviewed to budget for future capital expenditures, maintenance costs or replacement intervals. They also should be reviewed when fine-tuning mine plans. Good records will allow projection of future production based on past production with various borehole sizes, powder ratios or fabrics, patterns, and borehole depths, etc. They will also help forecast operating and maintenance costs for drills, dozers, loading equipment, trucks and crushers.

Due to the complexity of the needs, most companies have forms that prompt the blaster for information each step of the way. Accurate and complete records are essential for inventory and promptly identify safety exposures. Explosives security during storage and transportation is particularly important. Explosives theft is dangerous to the public and adds to the cost of doing business. See chapter 2 for these record keeping and security details.

A responsible person should always make records at the time of the event. For most records, the "responsible person" will be, or be delegated by, the blaster-in-charge, under whose direction all matters must be considered. But if closely supervised, apprentice blasters can complete many of these records as part of on-the-job training. In fact, the proper completion of records should be part of all training for new hires, and also part of the ongoing evaluation program for all employees.

All records should be clean and legible. The blasting site work environment often makes this difficult due to weather and dust conditions. But given the potential of these documents, from project personnel to regulators, lawyers and the public, the records must look professional. In some locations the records must be made available to the public upon request. Promptly providing complete, legible, professional-looking documents illustrates the professional nature of the workforce and serves as a favorable public relations tool.

As a final suggestion, each company should practice in-house quality control by assigning a qualified person to carefully review blast records from all blast crews at the end of each day or shift. Problems with completeness, legibility or accuracy can then be noted and legitimately corrected by the appropriate blaster before the next shift begins, or before an official copy is given to a customer. The quality control person should know the site-specific blast plan conditions at the various job sites, and be able to quickly recognize potential compliance problems and seismograph maintenance issues by examining the waveform printout. Effective in-house quality control of blast records will enhance the professional image of the blaster and blasting company in the eyes of customers, regulators and the public, and greatly reduce liability.

This chapter will focus on: (1) blast logs for documenting how a blast was designed and implemented, (2) blast vibration records for proving compliance with regulatory limits or recommended standards, and (3) preblast surveys for documenting the preblast conditions of houses and other structures, enhancing public relations, and modifying blast design. All three types of records facilitate post blast assessment and liability protection purposes. And, most importantly, they are all legal documents that will be scrutinized by other blasting professionals, project management personnel, regulators, insurance adjusters and attorneys.

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## BLAST LOGS

Blast logs are critical for inventory tracking and quality control and are generally considered "eye witness" testimony by the courts as to the blast event that day. The blast log should contain enough detailed information that another blaster could reasonably be able to reconstruct the blast at the same location in the near or distant future. In the near future the blast logs can be used to track explosives costs per unit volume to justify budgetary needs or negotiating pricing for future contracts. In the distant future the blast logs may be useful in litigation for either contract disputes or damage claims. During litigation, a defendant is placed in an extremely precarious position when past blast results must be recreated from inadequate or incomplete blast logs using explosive products and supply sources, drill logs, and bills of lading.

Blast logs are the basis for forensic investigations to evaluate blast design adequacy, explosive product performance, fragmentation success, work force performance, cost analyses, and adverse effects. Absent detailed information of the explosives placement throughout the rock mass in terms of the amount of explosives in each borehole and initiation sequencing, post blast assessment of fragmentation, detections of movement, flyrock, etc., is difficult to assess.

The successful performance of each blast is largely determined by the results of the previous blast. If a blast performed well, then the subsequent blast may be planned in the same way. For a poorly performing blast, the blast log can be used as a starting point for design modifications. Then, with successive blasts, the blast log provides a running record of design changes that result in favorable or unfavorable outcomes. This review process is critical for fine-tuning blasting programs to minimize costs and adverse impacts. Furthermore, blast logs can provide a historical track record for a new blaster assigned to the site, thus ensuring a smoother transition and greater chance for success.

Every blast log should contain the minimum information listed in table 27.3 to ensure sound documentation. The accuracy of these data is dependent upon field conditions. When giving names of companies and people, be very specific and leave no doubt about the named party. Numeric fields should generally be reported with at least 3 units except for explosives that need to be reported to the lowest level necessary for quantity tracking.

For underground or specialty blasting, many of the blast log details should remain the same except that the terminology might be slightly different because the borehole orientation becomes a less significant factor or no boreholes may be used as in demolition blasting.

Local, state or federal regulations may require specific formats and/or information. When requirements are beyond those listed above, simply add the new items to the list. If less information is required, prudent business practices dictate using the more informative set of guidelines. An example blast log is shown in figure 27.1.

Blasters must be consistent in their understanding and use of the many technical terms on the blast logs and other related documents. Therefore, companies should have clear and concise training rules that define the terms to be used for all company records. Additionally, the necessary level of accuracy should be specified. For example: "ANFO will be measured to the nearest kilogram (pound)" and "detonators will be reported by the unit." All efforts should be made to avoid conflicting data.

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## Minimum Blast Log Entry Information

| Entry |
|-------|
| Name of the project/permit and identification number |
| Name of the general contractor or mine operator |
| Geographic location of the blast (town, city, borough, etc.) |
| Location of the blast within the project/permit area (preferably GPS coordinates) |
| For production blasts, the number of the mineral seam and pit number |
| For quarry blasts, the wall and level of the blast, such as "east wall, 3a level" |
| Type of blast (Production, pre-split, trench, etc.) |
| Name, signature, and certification/license number of the blaster conducting the blast |
| Date and time of the blast, to the nearest minute |
| Weather conditions including temperature, cloud cover and wind direction/speed |
| Type of material blasted (e.g. sandite, granite, concrete) |
| Number of boreholes |
| Borehole diameter, depth and subdrill length |
| Face or bench height |
| Burden and spacing |
| Manufacturer, type, and amounts of explosives used in the blast |
| Total weight of explosives used in the blast |
| Type and length material used for stemming and decks |
| Powder factor or powder ratio |
| Sketch of the blast pattern to include: |
| - Pattern dimensions |
| - Free faces |
| - Face orientation in compass degrees |
| - Site conditions such as previous muck material left against a face, or boreholes that were not loaded |
| - Total amount |
| Initiation of shot boreholes: |
| Typical and atypical borehole cross sections to include: |
| - Primer locations |
| - Charge heights |
| - Stemming |
| - Decking |
| - Borehole conditions |
| Initiation system and delay sequencing |
| Weight of explosive/borehole |
| Maximum weight of explosives detonated in any 8-millisecond period |
| Maximum number of holes detonated in any 8 millisecond period |
| Make of delay product used |
| Identification of the nearest dwelling or public structure by name or reference number |
| Actual scaled distance to the nearest dwelling or public structure |
| Direction, in degrees, and distance, in meters (feet) from the nearest blast hole to the nearest dwelling or public structure |
| Blasting seismograph monitoring data summary – location, distance, scaled distance, peak particle velocities and associated frequencies, and air overpressure |
| Reasons and conditions for an unscheduled or reduced blast |
| Comments dealing with delays, or abnormalities during the loading process |
| Comments or directions if any information on the blast log varies from the specific blast plan conditions |
| Members of the blast crew and the name of the person(s) responsible for drilling |
| Results of post blast inspection |
| Vibration monitoring data including seismograph printouts, drill logs, bore profiles, bore tracking, webcam, etc. |
| Requested information, blast results |
| Was fly material controlled? |

*Table 27.3 – Minimum blast log information.*

For example, data may conflict when a company uses the blast log for billing. In one case the borehole depth recorded was the depth to the contrived bottom of the trench. Undercharged, the feet of subdrilling. When the blast log was reviewed, the height of the stemming was equal to the borehole depth. In essence, it appeared that no explosives could have fit into the borehole.

The degree of accuracy for weight and distances is also a subject for training. Weights can only be as specific as can be measured in the field. For example, ANFO to the nearest pound or 10 pounds may be all the blaster can measure for a bulk product. Take care to avoid "too much" accuracy. Use of a calculator to divide the total weight of explosives in a blast by the number of holes may provide a weight with two or three digits to the right of the decimal point, but that degree of accuracy is not realistic or attainable in the field. Accuracy considerations for each of the critical blast log parameters are discussed in the next section.

To ensure high quality records, each operation should periodically conduct internal reviews or audits. Management should audit the blast logs to see that they are correct and complete and that the various data do not conflict with each other. There are computer programs like the Blast Log Evaluation Program (BLEP) used by Office of Surface Mining Reclamation and Enforcement (OSM), which is an Excel based system where the various data fields are entered, cross tabulated and graphically compared. A simple audit system would compare the volume of a borehole with the weight of explosives reported in the borehole, to ensure that the amount of explosives reported as a borehole can fit into the given volume of the borehole. A loading density chart and a calculator is all that is needed for this task. Other calculations may identify that the height of the explosives column after the reported amount of explosives were loaded did not leave room for the length of stemming reported on the blast log.

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## Critical Blast Log Parameters for Liability Protection

Blast log information is critical for evaluating ground and air vibrations generated by blasting for liability protection. First and foremost, each line item of the blast log form must be completed to ensure admissibility in a court. Missing data or mismatured line items quickly undercut the validity of the record and the credibility of the blaster. For example, a record is unassigned by the blaster or has multiple line items that were left blank may be unattainable in court. If the line item simply does not apply to a company's circumstances and are not required, remove them from the form. If the form has line items, which are required by regulation but are not applicable for a specific blast, write "Not Applicable" or "N/A" on those lines. As for any matter entered on the form, make sure each number is followed by its associated unit of measurement, be it centimeters (inches) for borehole diameter, meters (feet) for borehole depth, burden, etc., or kilograms (pounds) for total weight of explosives.

As discussed in chapter 26 (Vibration) spatial relationships, blast orientation and blast design cause variations in vibration levels. Therefore, the most critical blast log items for liability control are discussed below and generally apply only to surface blasting operations. Accurate documentation of these parameters should allow vibration estimation in all directions from the blast site by using site-specific vibration attenuation relationships or national references.

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### Blast Locations

The blast location is where the blast site is located within the project/permit boundary. The blast location will allow distance calculations not only to the nearest structure but also to any other structure where a seismograph may be required for compliance or where vibration estimates are needed. The preferred method is to use a WAAS (Wide Area Augmentation System) - enabled Global Positioning System (GPS) unit to acquire latitude and longitude coordinates of the blast site. In fact, WAAS-enabled GPS is the best technology currently available for this. In almost all blasting applications, a clear view of the sky is possible for proper accuracy from the GPS unit.

When acquiring and reporting GPS coordinates of blast sites, it is important to consistently use the same techniques throughout the project or mining area. If only one GPS point (i.e., one pair of coordinates) is desired to represent the blast site location, always acquire that point at the same spot for every blast, such as the initiation hole, or the hole closest to the nearest dwelling. And make sure that all blasters know and use the same method. For larger blasts it may be necessary or desirable to acquire and report four GPS points to represent the four corners of the blast site. At some projects or mining operations, rock removal will be done in two or more lifts; resulting in highly similar GPS coordinates for blast benches at different elevations. In such cases, the lift or bench level should be reported along with the coordinates.

In lieu of the GPS method, a grid map may be available to identify and report blast site locations. However, to ensure accuracy, a project engineer or surveyor should help the blaster-in-charge determine the grid map coordinates of each blast site. Furthermore, it may be necessary to identify the date of the grid map, as some maps based upon aerial photos may be redone as the mine or quarry is developed, and the grid map nearby be dated or even relabeled in a different fashion over the original.

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### Distances

All reported distances are critical and should be verifiable based on the blast location. As with locating blast sites, a WAAS-enabled GPS unit is the best technology for measuring and reporting distances to the nearest dwelling or public building, as well as other compliance structures and seismograph locations. Before blasting begins at a project or mining area, GPS coordinates should be acquired and logged as "waypoints" at all protected compliance structures in every direction. The waypoints should be labeled such that any blaster using the same GPS can quickly identify the structures to which they pertain. And for the purpose of referencing project or mine maps, the GPS unit should be set on true north instead of magnetic north, because the grid lines on most maps are aligned with true north.

Before blasthole loading begins, the blaster should select "nearest waypoints" on the GPS unit's menu, then walk to each corner of the blast bench and record the distance, in meters (feet), and azimuth, in degrees, from the nearest blasthole to the nearest dwelling or public building. Distances and azimuths to other compliance structures should be determined and recorded in a similar manner. Once all critical distances have been recorded, scaled distance equations (See chapter 26, Vibration) can be used to calculate the maximum allowable charge/weight per delay, and determine at which structures a seismograph must be used for compliance.

A few precautions are necessary when using GPS for determining distances from the blast site. First, if a critical compliance structure or seismograph location is less than about 30.5 meters (100 feet) away, the accuracy of the GPS unit may not be sufficient. This is especially true for GPS units that are not WAAS-enabled, or when conditions prevent reception of a strong satellite signal. At such short distances a more precise measurement tool is preferable, such as a laser ranging device, a long measuring tape, or traditional survey equipment. And second, GPS measurements should be frequently checked against a map of the project or mine area, to confirm that all potential compliance structures and seismograph locations are being addressed and properly identified. In other words, do not rely entirely upon GPS.

In the absence of a GPS unit or other modern measuring devices, a map and compass may be used to determine blast site locations and distances/directions to critical structures. However, this method combines a chain of potential multiple landmarks (which is not likely at many sites), and knowledge and skills that are beyond the abilities of some blasters.

For vibration prediction when scaled distance is the basic criterion (See chapter 26, Vibration), it is critical to measure (and not estimate or guess) the distance from the nearest hole to the structure of concern. If a seismograph is used for monitoring, the distance to the seismograph must also be specified, and is especially important when plotting data for a regression analysis (See chapter 26, Vibration). Like the blast location, permanently recorded GPS coordinates at structures and monitoring locations allow distance calculations at any time, even months or a few years later when damage claims may arise.

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### Face Orientation and Direction of Blast Initiation

The blast pattern sketch should clearly show the hole positioning, initiation hole and delay sequence, and free face locations and orientations. As holes begin to detonate away from the free face, the spatial orientation affect the vibrations. Generally, ground vibrations will be strongest in the direction away from (behind) the free face and still stronger in the direction of initiation. Air overpressures will be strongest in the direction away from the free face (in front) and in the direction of initiation. Other confinement factors should also be identified on the sketch, such as a muck pile that remains against one side of the blast bench, or buffer material that partially covers the free face.

The face orientation may be identified by adding a north arrow to the blast pattern sketch or, better yet, by obtaining a compass azimuth (0° to 360°) parallel to the primary face, and showing that azimuth on the sketch.

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### Charge-Weight Per Delay

Charge-weight per delay is the single most controllable factor the blaster can use to minimize vibrations. All the blast log details should leave no doubt about the amount of explosives that detonated in any delay interval. To accurately determine the charge-weight per delay, the quantity of explosives in each borehole should be documented to the nearest whole weight unit. Do not average the charge-weight per borehole by dividing the total weight of explosives by the number of boreholes unless all the boreholes were exactly the same.

For nonelectric initiation systems, the sketch of the blast pattern should contain the delay intervals between the boreholes and rows so that the actual firing times of each borehole can be determined. Overlaps in timing can cause a significant increase in vibration levels. If the boreholes are decked, the timing of the decks must be shown to determine the charge-weight per delay. For electric sequential systems, the detonator delays and the sequential timer setting (delay between circuits) must be noted. And for electronic systems, the programmed firing time of each borehole or deck becomes a borehole count to be needed.

The maximum charge-weight per delay, when coupled with accurate distances, establishes the scaled distances for compliance with project specifications or regulations. For reporting purposes in many regulatory arenas, if the designed millisecond separation between any two boreholes in the entire blast pattern is at least 8 ms, the blaster is said to have "one borehole per delay." In that case, the maximum charge-weight per delay would simply be the maximum weight of explosives in any one of the boreholes. This time separation effectively mitigates the vibration energy of two charges from coupling together to generate a larger vibration (constructive interference). Vibration control becomes more complicated when the holes are decked or the delay pattern allows more than one hole to detonate per delay (i.e., in any period less than 8 milliseconds).

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### Blasting Seismograph Records

Vibration data provides for better liability protection than scaled distance values. The blaster must choose the blasting seismograph with the proper operational characteristics for the project and then properly deploy the unit in the field (See chapter 26, Vibration, for details on blasting seismograph set-up). Once a record is obtained the blaster must verify that the event is the result of the project blasting based on the waveform appearance and event time. Upon verification, attach the waveform record to the blast log and report, at a minimum, the distance, location, maximum peak particle velocity, associated frequency and air overpressure level on the blast log. In the event that the seismograph was not triggered by the blast, attach a printout from the seismograph showing the date and time the unit was armed and disarmed, and the arming and disarming trigger levels. If the seismograph cannot that type of verification, attach a handwritten statement containing the above information, the make, model and serial number of the seismograph, and the signature of the seismograph operator.

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### Retention Period

The blast record retention period should be as long as necessary to meet statutory or regulatory requirements in the project area. Typical time frames range from 3 years to 7 years, but may be longer. The records should be stored in a clean, dry environment to prevent yellowing and/or fading of paper. In particular, some of the thermal paper from blasting seismographs is sensitive to heat and light. Non-paper records like electronic blast logs, vibration waveforms and videos must be retained too. Back up any electronic data and store it in a secured location off site. The system used to back up these records should be reviewed periodically to ensure the data is backed up, and is retrievable.

![Figure 27.1a – Example of a blast record or log (front). (Courtesy: K. Eltschlager)](images/546.png)

![Figure 27.1b – Example of a blast record or blast log (back). (Courtesy: K. Eltschlager)](images/546.png)

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## BLAST VIBRATION RECORDS

Blast vibration monitoring is essential for liability protection and post blast assessment, and in many instances required by either contract specifications or regulations. Ground and air vibration data give validated information about the blast event and act as an indicator of what actually happened during the blast. If the blast design was sound but the vibrations were higher or lower than expected, one or more of the three causes listed in table 27.4 occurred.

### Causes Of Higher Than Expected Vibrations

| Cause |
|-------|
| The blast was improperly implemented in the field |
| One or more of the products malfunctioned |
| The monitoring equipment was errantly located or set up |

*Table 27.4 – Causes of higher than expected vibrations.*

Each blast should be monitored with a blasting seismograph that is compliant with the *ISEE Performance Standards For Blasting Seismographs* and deployed in the field according to the *ISEE Field Practice Guidelines For Blasting Seismographs* as discussed in chapter 26, Vibration. Each operator should be trained in the proper use of the unit and have to select monitoring locations near protected structures. Then once the event is recorded, the data must be printed and made part of the permanent record. But remember, a blast vibration record alone, unsupported by adequate blast log information, is virtually useless for liability protection or regulatory compliance. A blasting seismograph record should include the information in table 27.5.

### Seismograph Record Information

| Entry |
|-------|
| According the seismograph compliant with the *ISEE Performance Specifications For Blasting Seismographs* |
| The location of the seismograph identifiable to a structure |
| Make, model and serial number of the seismograph |
| Sensor and acoustic trigger levels |
| Name of the person operating the seismograph |
| Date and time of the record that matches the blast log |
| Distance and direction from the blast to the reading |
| Name of the person and firm analyzing the reading |
| Name of the person and firm analyzing the blasting seismograph record (if different from the seismograph operator) |
| Waveform printed of the event with summary information |
| Maximum ground vibration data for each of the 3 axis |
| Internal operations check or calibration pulse |
| Most recent shake calibration date (which should be within 12 months of blast date) |

*Table 27.5 – Seismograph record information.*

Be sure to establish communications between the blaster and seismograph operator for each event. This will ensure that the seismograph is in the monitoring mode when the blast is detonated. For example, a seismograph might be set up for a quarry blast and the unit triggers prematurely. Thinking that the unit was triggered by the blast, the operator begins removing the unit from the field, the actual blast goes off, and the event is missed. Cell phone or 2-way radio communications could have prevented the mishap. Note, however, that some seismographs might be triggered by radio communications within about 3 meters (10 feet). So avoid using a 2-way radio, be sure to allow enough time for the seismograph to record and/or before with another recording.

Lastly, the blaster must verify all vibration data obtained by a third party firm. Often the monitoring company reports the monitoring locations and distance to the structure. The blaster must ensure that these data match the blast log information.

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### Digital data

All blasting seismographs currently manufactured store digital vibration data. The digital data of each blast event should be archived for future use as post blast assessment or legal defense. As discussed in chapter 26, with the digital data the waveforms can be viewed, enlarged, or synthesized within the manufacturer's software. A typical waveform displayed on a computer is shown in figure 27.2. Computer programs allow the user to magnify the waveform for better resolution and evaluation of the data. Afterwards the event can be printed on a full sheet of paper.

![Figure 27.2 – Computer waveform display. (Courtesy: K. Eltschlager)](images/549.png)

Often the event is printed in the field and the digital data are deleted. The absence of digital data hinders any follow-up efforts to fine-tune the blasting program. Keep in mind that the equipment cost and personnel efforts expended to obtain the data are largely wasted if the digital data are discarded. Prudent business practice is to save all data in the most widely usable format. Current storage formats include USB drives, CDs, DVDs and computer hard drives.

A strong advantage of digital data is that the information can be remotely retrieved, stored and printed. Telephone lines, cellular towers and satellite receivers attached to seismographs allow remote and instantaneous access to the digital data after each blast.

> **Caution**
> Back up all data frequently.

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### Paper Printouts

Modern seismograph manufacturers strive to make printing events effortless for the blaster. As all modern seismographs store digital data, the events may be printed in the field or in the office. Units with on-board printers will provide strip chart printouts. Units without printers may have an accessory printer that can be attached in the field. Otherwise, the data must be downloaded to a computer and printed from the manufacturer's software. Keep in mind that site-specific location data should be entered in the field and not altered after the event for chain of custody purposes. As such, the paper printouts are primarily used for legal defense and regulatory compliance.

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### Strip Charts

Blasting seismographs with on-board printers will produce a strip chart printout. Years ago the ticker-tape printouts were challenging to read and required knowledge of what the fields meant based on where the "holes were punched" in the paper as shown in figure 27.3. Current units report all the information programmed into the unit at the time of the blast event and can display the full waveforms of the event.

![Figure 27.3 – Ticker tape printout. (Courtesy: K. Eltschlager)](images/550.png)

![Figure 27.4 – Trigger status printout. (Courtesy: K. Eltschlager)](images/550.png)

On-board printers may also have the advantage of reporting when a unit was activated (Trigger Active) and deactivated (Exit Triggered) as shown in figure 27.4. This strip can then be attached to the blast log for documentation of seismograph set-up. The blast log should show a blast event that happened between these two times or the reading may be invalidated. Also documented are the ground and air vibration trigger levels during the activation period. Some seismographs store activation/deactivation information digitally. Such information may be retrieved later, but this is hardware dependent.

A seismograph with an on-board printer immediately prints the strip chart as shown in figure 27.5 in the field for the blaster's review and attachment to the blast record. The strip chart has all the components of the digital record but may be difficult to read because of the smaller print and space limitations. And depending on the print options selected, the strip chart may be too long and difficult to reproduce or attach to the blast log. At a minimum, the waveform, summary data and calibration pulse must be printed. Then, based on the appearance of the waveforms, the blaster must verify that the event is the result of a blast before attaching the strip chart to the blast log. The blaster should also check for any anomalous readings and check the calibration pulse to assure the unit is functioning properly.

![Figure 27.5 – Strip chart waveform printout with summary and location data. (Courtesy: K. Eltschlager)](images/552.png)

Beware that the printer must be regularly serviced and provided with paper. Missed events because of the lack of paper or improper set-up gives the appearance of an incompetent seismograph operator and a less-than-professional attitude towards compliance with regulations. This may result in a public relations problem that reflects poorly on the entire blasting program. A strong advantage of field printers is that a second strip chart can be printed in the field and handed to the homeowner as a public relations tool and to show that the blaster has nothing to hide.

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### Full page reports

Some seismograph manufacturers and vibration consultants have developed their own forms and methods of reporting waveform data, typically in a full-page format. These printouts provide the highest resolution from the digital data and are easily attached to the blast log. The primary disadvantage to full-page reports is that they can only be printed with a computer printer. Figure 27.6 is an example that includes a full waveform analysis, the data in log of peak particle velocity and air overpressures are important. Figure 27.7 shows the same information with the addition of the USBM RI 8507, Appendix B frequency-dependent vibration limit for maximum probability protection from vibration damage. This graphic may be required to meet regulatory or contractual requirements. Whatever the printout, the blaster is responsible for printing the proper records to meet the requirements along with required additional analyses.

![Figure 27.6 – Full page vibration report with waveform. (Courtesy: K. Eltschlager)](images/554.png)

![Figure 27.7 – Full page vibration report with waveform and USBM graphs. (Courtesy: K. Eltschlager)](images/554.png)

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## PREBLAST SURVEYS

Preblast surveys (PBSs) are considered to be beneficial to both owners of structures and blasting personnel. The primary purpose of the survey is to establish a pre-blast baseline record as to the existing conditions of a structure, while providing an opportunity to communicate the project goals and positive measures designed to prevent damage to structures. It also provides the means to identify any structure or contents that may be particularly sensitive to vibrations. A well-done PBS will provide the blaster with the site-specific information necessary to design blasts to ensure minimum liability exposure. However, a hurried or low-budget survey can be more harmful than beneficial to the blaster.

Most importantly, a preblast survey must be completed prior to any blasting. If conducted after the first blast, the document is considered a "condition survey" and will not fully protect the blaster from certain claims of damage.

A PBS should be offered to all residents or owners of houses, buildings and other structures near the blasting area where the expected vibrations may exceed 12.7 millimeters/second (0.5 inches/second) or 133 decibels. When vibrations exceed these levels, complaints and claims of damage can be more likely. The aerial extent of the offering can be determined by an anticipated maximum charge-weight per delay for a project and an assumed or specified scaled distance estimate. To select the appropriate scaled distance for a given vibration level use the techniques described in chapter 26 Vibration. For the anticipated maximum charge size, the blaster must estimate a charge size based on the project requirements. This is normally part of the project proposal.

Many times the project specifications or regulatory requirements dictate the aerial extent of the survey, which can vary from 30 meters (100 feet) to 0.8 kilometer (½ mile) or greater. Occasionally a scaled distance is referenced to determine the aerial extent based on an anticipated vibration intensity. The maximum distance for the PBS offering based on a specified scaled distance is calculated using equation 27.1 (Scaled distance formula):

$$R = SD_2 \times W^{0.5}$$ <!-- VERIFIED -->

**Equation 27.1**

Where:
- $R$ = Distance from any potential blast site to offer a PBS (meters) (feet)
- $SD_2$ = Scaled distance factor (meters/kilogram^{0.5}) (feet/pound^{0.5})
- $W$ = Anticipated maximum charge weight of explosives (kilograms) (pounds)

SD₂ may be determined from the appropriate equations in table 26.3 in chapter 26 which is based on blasting type and desired confidence level. For example, at coal mines in the U.S., a vibration of 12.7 millimeters/second (1.5 inches/second) equates to an SD₂ of 41 meters/kilogram^{0.5} (90 feet/pound^{0.5}) based on the table's upper bound equation.

---

### EXAMPLE 27.1

Calculate the distance (radius) to which a PBS should be offered using a scaled distance factor of 41 and blasting a charge-weight of 10 kilograms.

$R = SD_2 \times W^{0.5}$ <!-- VERIFIED -->

$R = 41 \times 10^{0.5}$

$R = 41 \times 3.16$

$R = 130$

The distance within which the preblast surveys should be offered is 130 meters.

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### EXAMPLE 27.2

Calculate the distance (radius) to which a PBS should be offered using a scaled distance factor of 90 and blasting a charge-weight of 220 pounds.

$R = SD_2 \times W^{0.5}$ <!-- VERIFIED -->

$R = 90 \times 220^{0.5}$

$R = 90 \times 14.8$

$R = 1,335$

The distance within which the preblast surveys should be offered is 1,335 feet.

Typically, a letter offering a PBS is mailed or hand delivered to nearby residents and owners of structures out to these distances. If blasting is continuous in an area, the aerial extent may be expanded for liability protection. The letter is a critical piece of information from which the owner decides if they want to request a PBS. A good letter will convince the recipient to request a PBS. A letter with insufficient information about the purpose or cost of the survey may result in no action.

Figure 27.8 is an example of a PBS notification letter, which should contain the following items in table 27.6.

### Preblast Survey Letter Content Items

| Content Item |
|-------------|
| Company letterhead |
| Name of company, mine, or contractor |
| Mailing address |
| Telephone number |
| Location of the mine/project |
| Date blasting will begin |
| Explanation of a preblast survey |
| Who to contact for scheduling (name & phone) |
| Statement of free cost to landowners (if applicable) |
| Request date based on the date blasting will begin |
| Reason why a PBS should be done |
| Person's name responsible for completing the survey (name & title) |

*Table 27.6 – Preblast survey letter contents.*

The PBS procedure also serves to establish a dialog and explore avenues of communication between blasting company and neighboring residents. Making arrangements to conduct a survey is often the first contact the blasting company has with the nearby public. When hiring a PBS inspector, the blasting company should provide sufficient blasting information to the inspector to effectively communicate with the public and generate positive public relations. Every contact should be professional and courteous. Good first impressions nearly improve the skeptical nature of most people living near proposed blasting activity, but bad first impressions can unfavorably jade the public's opinion.

---

### Preblast Survey Documentation Process

A PBS may be conducted by the blaster, a consultant, or other specified party. Most often, consultants are more neutral since they serve as an unbiased party and can conduct the surveys expediently. In either case, the blaster has a strong incentive to limit liability with a detailed survey. Keep in mind that some PBS consultants may not be knowledgeable about the blasting activities and are at a disadvantage in conducting public relations activities. Therefore, the selection of a good preblast survey party is a very important business decision. A good PBS inspector will make keen observations, provide good documentation, and briefly explain the project goals and general measures to protect the owner's structures, such as the use of certified or licensed blasters, vibration limits, and seismographic monitoring. Also, a carefully crafted pamphlet may be left with the owner to supplement the oral communications.

![Figure 27.8 – Example of a preblast survey notification letter. (Courtesy: K. Eltschlager)](images/557.png)

The scope or details of a survey may vary widely because of the differing levels of risk exposure. For example, at a demolition site where air overpressure is expected to be high, a PBS may be very detailed and/or focus on window conditions. In another instance, a remote mining operation may have surveys conducted with minimal detail because the expected vibration levels will be low and the PBSs is required by regulation. However, regardless of the reason, if the PBS has minimal detail, the blaster may be held responsible for cracks that were pre-existing and not documented in the PBS.

The survey normally focuses on residential structures with secondary emphasis on the outdoor property. The contents of the structure need not be part of the survey, but information about contents can be useful to alert the property owner and blaster of potential problems. Outside the structure, the survey assessments are generally limited to the visible surface conditions including inspection of out buildings, garages, walls, water systems, swimming pools, pipelines, cisterns, and utility lines. In certain instances water samples may be taken to document water quality, static water levels in a well, and/or flow rates from developed springs may be measured to document volume. For underwater inspections such as in-ground swimming pools a glass bottom box may be used to inspect for the presence of hairline cracks. Also pay particular attention to structures where one end is supported on bedrock and the other end fill.

To be most useful to all parties, the PBS report should be in written form, and include notes and diagrams that clearly document the condition of the structure. Photos and/or video may be used to support the written survey. If photos are included, they should be identified in a manner that allows quick reference to the actual location of the defect or condition as it or on the structure. Photographs and video have a greater impact than sketches and are less subject to interpretation. However, photographic and video documentation is strongly affected by proper lighting. Side lighting of a crack casts a shadow that provides the best resolution. Direct lighting like the flash from a camera provide the worst resolution. A combination of sketches and photographs will always provide the highest level of liability protection. In a similar fashion, videos should not significantly narrated. It is also essential that each PBS report clearly identifies the information listed in table 27.7.

### Preblast Survey Entry Information

| Entry |
|-------|
| Property (physical address) |
| Property owner |
| Current resident (if different from owner) |
| Date and time of survey |
| Name and signature of person who conducted the survey |
| Project/permit name and identification number |

*Table 27.7 – Preblast survey entry information.*

A comprehensive form will guide the surveyor through the process without missing any details. It also helps keep the surveyor on track so he or she converses with the owner. As with all forms, each line item should be addressed. The survey should provide a basic description of any preblast building defects and any physical factors anticipated to be particularly sensitive to blasting. The preblast survey must be of sufficient detail and quality that the blaster, insurance adjuster or regulatory investigator, in the event of a blasting damage allegation, can review the survey to determine if the condition was pre-existing.

> **Caution**
> It should be noted if an item is not applicable.

For the interior, the survey should clearly document, for each room in the house, existing conditions such as: cracks, water stains, wallpaper ripples, gaps in wall and ceiling joints, gaps where cabinets and countertop meet walls, loose or popped ceiling tiles or wood trim, cracks or missing grout in tile walls, and floors, doors and windows that are difficult to open or close, floors that squeak, loose ceiling fixtures, cracked or fogged windows, and basement wall and floor cracks and conditions. For the exterior, the survey should document foundation wall cracks and conditions, cracks and defects in home siding materials, cracks and differential displacements in concrete patios, driveways and sidewalks, missing or clogged gutters and downspouts, cracks and loose mortar in masonry walls and chimneys, missing or worn shingles, and "wavy" roof surfaces. Remember that hairline cracks are particularly important to note because they are generally the first expression of vibration damage to a structure. If not adequately documented, a homeowner may see the old cracks, believe that blasting caused them, and file a damage complaint or claim.

Lastly, the person conducting the survey should sign the written PBS report and a copy should be provided to the resident homeowner. A PBS is an official document to be retained at least until the project is complete, or, preferably, until the liability period or "statute of limitations" prescribed by law for that jurisdiction has expired.

---

### Use of Preblast Surveys By Interested Parties

A PBS protects everyone's rights. Claimed damages in a house that are not documented in the PBS are, from the owner's perspective, presumed to be from the blasting. For this reason, it is in the blaster's best interest to have a thorough and accurate survey done. Conversely, the survey protects the blaster from unjustified claims when the cracks or other damages were clearly observed and documented prior to blasting.

Two parties—the person requesting the survey and the blaster—have an interest in reviewing a PBS report upon completion.

---

### Person Requesting the Survey

The person requesting the survey should review the PBS for accuracy. Since the PBS will form the basis for any future claims, any discrepancies that are found should be described in a written letter to the PBS inspector. Depending upon the nature of the discrepancy, the PBS inspector may decide to simply attach the letter to his client's copy of the PBS report, or revisit the structure, create an addendum to the original PBS report, and distribute the addendum to all interested parties.

---

### Blaster

The blaster should also review the PBS reports for accuracy and note the types of buildings near the blasting area. If unique structures (e.g., historic buildings), unusual structures (e.g., water towers and high-rise buildings), or buildings that house sensitive equipment or procedures (e.g., hospitals, MRI and CT diagnostic centers, and laser surgery clinics) are identified during the PBS inspections, the vibration limits may need to be modified as described in chapter 26, or blast scheduling might need to be carefully coordinated with the administrator of a particular building. When buildings with valuable and fragile contents are identified, the blast vibrations may be reduced or the contents may be removed to a safe location until blasting is complete.

Preblast surveys associated with important historic, cultural or archaeological resources should attract the special attention of the blaster. Other structures may require more careful blasting to ensure damage prevention. Archaeological sites may be invaluable and require mitigation of the resource prior to blasting. In some instances, special monitoring or reduced blast limits may be prudent. Blasting near any such resources should always be coordinated with the local preservation authorities.

---

### Limitations of Preblast Surveys

A PBS report documents the general state of cracks and other defects prior to blasting, but does not explain the causes of such defects. Although useful, a PBS report is not the total answer to assessing the causes of all damages, claimed or otherwise. Preblast surveys do not show the influences of non-blast forces which may continue to act in creating new cracks, widening or extending existing ones, or, in some cases, closing some in response to cyclic forces such as temperature, humidity, frost, and soil hydration. For this reason, it is necessary to use a PBS report as just one of several tools to evaluate possible blasting impacts. Other tools include an assessment of the nature of cracking, observations of conditions in and around the structure that might have changed since the PBS was conducted, and an evaluation of the vibration amplitudes experienced by the structure, based on blast log information and all available seismograph data.

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## OTHER SUPPORT DOCUMENTATION

Other records are developed to track communications, explosives inventory, employee use and billing. These documents may be attached to the blast log to support the level of work conducted to document safe and productive blasting operations. Table 27.8 lists these documents. They will all be called into evidence in the event of litigation.

### Other Support Documentation

| Document |
|----------|
| Drill log report (See chapter 18) |
| Borehole loading log (Explosive use report) |
| Explosives Inventory (Magazine inventory) |
| Explosives use report |
| Project to Gilt maps |
| Hole density checks |
| Bills of lading (See chapter 2) |
| Work hours |

*Table 27.8 – Other supporting documentation.*

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## SUMMARY

Blasting records serve many purposes and should not simply be viewed as a "paperwork" exercise. To the contrary, they provide a wealth of information that can verify disputed facts, justify blast design changes, prove compliance to the regulators, minimize liability exposure and promote sound public relations.

Production optimization is a side and consequent manner should be the primary goal of the blaster. Successful blasters use multiple documents to keep track of where they have been and where they are going.

The regulators want the blaster to document explosives movement in many ways. In the U.S.A., ATF wants to know if the magazines are safe and security and whether all of the explosives are consumed. At the state level, state want to know what blast USENET means to know what the local and limited the proper detonation are safeguarded from the vibration. OSHA wants to know if the blaster and crew are using the products safely. OSM wants blasters to be certified and document how the explosives are used to control the adverse effects of blasting. And lastly, the police, and legal experts expect that blasting professionals use the utmost care in the storage, transportation, handling, and detonation of explosives. With many states' strict liability laws in explosives cases, blasters can ill afford errors in the documentation of all blasting-related operations.

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## ADDITIONAL RESOURCES

Dowding, C. H. 1996. Construction Vibrations, Prentice Hall, Englewood Cliffs, NJ.

Siskind, D. E. 2000. Vibrations from Blasting, International Society of Explosives Engineers, Cleveland, OH.

Rosenthal, M. F. and G. Morlock. 1993. OSM Blasting Guidance Manual, Office of Surface Mining Reclamation and Enforcement, Washington D.C.

Eltschlager, K. K. 1997. Put your money in your paperwork, International Society of Explosives Engineers (ISEE) Proceedings on the 23rd Annual Conference on Explosives and Blasting Technique, February 2 – 5, Las Vegas, NV. ISEE, Cleveland, OH.

Perdue, K. 1999. Explosive records for blast damage litigation through accurate record documentation, International Society of Explosives Engineers (ISEE) Proceedings of the 16th Annual Conference on Explosives and Blasting Technique, February 4 – 9. Orlando, FL. ISEE, Cleveland, OH.

Konya, C. 1991. Blasting demolition: A simple method for saving and retrieving blasting data, International Society of Explosives Engineers (ISEE) Proceedings of the 17th Annual Conference on Explosives and Blasting Technique, February 3 – 7, Las Vegas, NV, Cleveland, OH.

Nicol, F. M. 1993. Blast Data Management for Effective Claims Control, International Society of Explosives Engineers, Cleveland, OH.

Ecton, J. E. 1997. Presurveys – The key to good public relations, International Society of Explosives Engineers (ISEE) Proceedings from the 4th Annual Conference on Explosives and Blasting Technique, January 31 – February 2, New Orleans, LA. ISEE, Cleveland, OH.

Lusk, B. and A. Aimone-Martin. 2003. Placing the pre-blast survey as a vehicle to promote good public relations – a case study, International society of explosives engineers (ISEE) Proceedings from the 29th Annual Conference on Explosives and Blasting Technique, January 31 – February 5, Anaheim, CA. ISEE, Cleveland, OH.

Harrison, D., Walter, E. Jr. and Ferek, M. 1995. Pre-blast Surveys; a Public Relations and Claim Reduction Tool, International Society of Explosives Engineers, Cleveland, OH.

Harrison, D., E. Walter Jr. and M. Ferek. 1995. Pre-blast surveys; a public relations and claim reduction tool, International society of explosives engineers (ISEE) Proceedings of the 21st Annual Conference on Explosives and Blasting Technique, February 5 – 9, Nashville, TN. ISEE, Cleveland, OH.

Eltschlager, K. 2001. Regulatory review of blasting related citizen complaints, International Society of Explosives Engineers (P) Proceedings from the 27th Annual Conference on Explosives and Blasting Technique, January 28 – 31, Orlando, Fl. ISEE, Cleveland, OH.