To: Honorable Mayor and Members of Town Council
From: Norris W. Croom III, Fire Chief
Title
Update: Construction Blasting Overview (Item to be Continued to April 7, 2020)
Body
________________________________________________________________________________
Executive Summary
Construction Blasting:
Construction blasting involves detailed geological engineering and calculation of the proper amount of explosives needed to achieve the desired objective of breaking up solid underground formations. In order for engineers to determine the blasting pattern and amount of explosives needed, they must attempt to understand the geological structures under the ground. Core samples throughout the projected blast area are taken to enhance the engineer’s knowledge. Unfortunately, not every geologic pattern can be determined through these random core samples of an area.
History of Blasting in Castle Rock:
Construction blasting for roads, utilities, and development needs have occurred in the Castle Rock area for many years. Prior to 2013, Castle Rock Fire and Rescue provided general guidance and oversight on a number of blasting operations, but did not maintain detailed records of the permits or inspections of these blasting operations. In discussion with the two primary blasting companies who were known to have done work in the area, it was determined that approximately 100 such blasting events occurred prior to 2013. Representatives from these companies were aware of some complaints involving the blasting, but the complaints were handled by the fire department, and they didn’t know the final outcome. The representatives also indicated that most of the blasting occurred in densely populated areas where new developments were being constructed.
Since 2013, the Life Safety Division began maintaining detailed records on permits and inspections of blasting events which have occurred in the jurisdiction. These records confirm the following:
-28 blasting permits have been issued. Some of these permits involved only one or two blasting events, while others involved more blasting events at the site.
-68 blasting events were inspected and witnessed by the Life Safety Division. Two blasting events resulted in property damages that have been, or are being, resolved by the contractors or the blasting company.
Code Requirements:
For many years, the Fire Codes have provided permit authority for blasting operations to the Fire and Rescue Department. However, the requirements for blasting were vague and very high level. The Life Safety Division has internally adopted more restrictive guidelines for all blasting operations that must be followed. Some of these include:
1. The most restrictive requirement imposed in 2015 involved limiting the ground vibration thresholds allowed to 50% of industry standards. These ground vibrations are measured by the proper placement of seismic monitoring devices around the blasting site.
2. Seismic monitor placement must be approved by the Life Safety Division, with results being provided for review.
3. The blaster must provide pre-blast written notifications to property owners within 1,000 feet of the blasting area. These notifications must specify the day of the week and time frame in which blasting may occur.
4. The Life Safety Division limits all blasting on a site to not more than two days a week, with a specific time frame for blasting. The Town Public Works Department must also approve the days and times as part of the blasting operation traffic plans.
5. A Life Safety Division Inspector must be present at each blasting event to conduct inspections and document any concerns or consequences in an inspection report.
6. After each blasting event, the Life Safety Division completes a blasting After Action Review (AAR) report with any corrective actions identified to the blaster. The report also details any complaints or damages and holds the contractors responsible for corrections.
Current Requirements (based on recent changes)
As a result of two recent incidents involving blasting fallout that left the immediate blast pattern, the Life Safety Division implemented additional requirements as follows:
1. The blaster must provide a written pre-blasting plan prior to each event for review and approval by the Life Safety Division. This plan will be verified at the pre-blast site inspection.
2. All blast patterns must be covered with approved blasting mat material to reduce the possibility of debris being thrown from the blast pattern. These mats pose additional challenges in the fact that wind can cause them to be disrupted which can loosen the wires to the firing system and ultimately may delay the firing sequence.
3. The Life Safety Division must also be present at each blasting event, conduct the required pre-inspection, and complete slow motion, high resolution video using UAVs to evaluate the blast for any future corrective actions.
4. Any roadway within 1,000 feet of the blasting pattern will be required to be closed during the blasting event.
5. Seismic monitoring is placed in close proximity to any dwelling or vulnerable asset within 500 feet of the blasting pattern. This will provide the highest degree of ground vibration monitoring to ensure that structural damages are not being created by the blasting.
6. Any complaints received as a result of the blasting are promptly investigated by the Life Safety Division, and confirmed damages are passed along to the blasting and construction company for immediate corrective action with subsequent follow-up by the Life Safety Division.
7. After each blasting event, the Life Safety Division reviews the UAV video, seismic monitor readings, and any complaints received. A final blasting AAR report is completed with any corrective actions identified to the blaster.
8. No additional blasting will be allowed to occur until all corrective measured identified have been implemented.
Challenges Associated with Blasting:
Blasting has and always will pose concerns to the general public. The thought of using explosives to disrupt the earth in proximity to homes, businesses, or other areas will always pose concerns to the community. The Fire Code allows such blasting operations to occur, and the Life Safety Division has adopted more stringent compliance guidelines than provided in the Fire Code. The consequences of not conducting construction blasting could significantly impact or even prevent development of many areas. Without construction blasting, it may not be physically possible to develop roadways, install underground utilities, or build homes with basements in some areas of the community.
There will always be unpredictable geological features under the surface where blasting occurs that could cause even the best planned blasting event to launch debris into the air. As already noted in recent blasting events, the use of the blasting mats has resulted in some partial failures and flying debris. The Life Safety Division has implemented the highest level of safety into each blasting event in an effort to reduce the likelihood of debris being thrown from the site, but it is impossible to suggest that it may never occur.
The momentary “boom” heard by nearby properties poses no danger to the community, but often generates a number of complaints. This momentary blasting event can loosen significantly more rock formations than the constant pounding from hammers or excavation equipment chiseling away at the rock every day for extended periods of time.
In closing, we are continually reviewing our processes and procedures. While blasting operations have occurred throughout various areas of town over the years, each area poses its own challenge based on geological features, the density of buildings and roadways, and the amount of work to be done. Our first and foremost priority is to ensure the safety of our residents and visitors, and we will continue to review every operation to determine if additional changes are required.
Additional Information:
Additional information pertaining to construction blasting and requirements can be found on the Castle Rock Fire and Rescue Department WEB Page, and are identified as:
• Blasting Information 01-31-2020.
• General Blasting Information FAQ