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I determined that the seismograph used by the company during the six blasts reviewed did not comply with the regulatory requirements pertaining to annual seismograph calibration. I also determined that the blast records did not contain a record of a calibration signal of the seismograph's gain setting. As such, I was unable to use the seismograph's airblast level recordings to determine whether the six blasts reviewed were in compliance with State regulatory airblast limits. I was also unable to use the seismograph's ground vibration recordings to determine whether the six blasts were in compliance with State ground vibration limits. The company did not correctly use the mathematical formula and table found in the Regulations in several instances, due to inaccurate data or incorrect implementation of the formula. I was, however, able to use or derive information from the blast logs pertaining to the amounts of explosives detonated per any 8-millisecond interval during the six blasts. By reconstructing the blasts from the logs and pattern sketches, by utilizing the regulatory formula and table pertaining to the relationship between peak particle velocities and the amounts of explosives used per 8- millisecondblast interval, and by utilizing the more restrictive cases where differing values of distance and explosive weights were reported on the logs, I determined that the company did not exceed the applicable regulatory limits for ground vibration. Whether the six blasts reviewed created airblast and ground vibration within State regulatory limits does not mean that some level of airblast or ground vibration did not reach to the azea of the rockfall. However, based upon my review of the information obtained, airblast and ground vibration from the six blasts reviewed were not the only possible causes for the rockfall. Some of the individuals interviewed in this investigation indicated that rockfall is a common occurrence along State Highway 12, though these individuals also indicated that there had been very few calls requesting rockfall clean-up up to the day of the rockfall. Some of the individuals interviewed additionally indicated that some of the causes of rockfall along State Highway 12 are precipitation (rain as well as Snow) and high wind. One mine employee interviewed indicated that rainfall had occurred in the area of the rockfall during the days immediately preceding the rockfal event, and two non-mine employees interviewed indicated by rain and high wind had occurred in Trinindad, Colorado on 5(22(02 and 5(23(02, though Trinidad is situated approximately 16 miles east of where the rockfall occurred. Statements that rainfall occurred during the days prior to the rockfall can be corroborated by the blast log for the 5/20/02 blast that documents the weather on that day as "cloudy and rain". Statements that rainfall occurred during the days prior to tree rockfall can also be somewhat supported by the evidence of seepage visible on the south-facing highway cut observed during my inspection of 5/24(02. As such, while the possibility that natural precipitation was the cause of the rockfall cannot be conclusively determined, it can neither be eliminated. Based upon my investigation and evaluations of the information reviewed, evidence clearly indicating that the cause of the rockfall that occurred on 5/23/02 was directly related to the blasts from the Lorencito Canyon coal mine that I reviewed was not found.