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CONDITION #10 ALLOWS BLASTING 200 FT FROM MISSION GORGE RD & 275 FT FROM MARIPOSA.
• This is not safe. • This is unfair to residents. • This violates an important purpose of the CUP--to safeguard the community. |
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Condition # 10 of the Conditional Use Permit (CUP) currently states:
“Within the area between Mission Gorge Road and the San Diego River, blasting will be precluded within 200 feet of the Mission Gorge Road right-of-way and within 275 feet of the northeasterly property line adjacent to the Mission Pacific residential neighborhood.” Mining this area will benefit those who want to see as much economic gain as possible.
The Mission Gorge Quarry has high quality stone that is used in the production of asphalt and concrete and that is becoming scarce. Additionally, because transporting asphalt and concrete is costly, having a mine nearby decreases the cost of these products for both general industry and government infrastructure projects, such as roads. Local governmental bodies, such as the City and the County, are major users of concrete products because of all of the roads and infrastructure they need to build and maintain. Local industry will enjoy reduced prices. The City and County want industries to find San Diego a place where they can grow. It builds their tax and employment base. However, conditions will become much worse for nearby residents. * Dust, noise, vibrations, and damage to homes, which are already a problem, will intensify. * The ability to use and enjoy their property will decrease. * The threat of flyrock causing injuries or property damage will rise significantly. * Nearby neighbors have already suffered from the negative impacts of living close to the quarry. * Bringing the blasting even closer will be a clear message to nearby neighbors that they are expected to live with even worse conditions. * Nearby neighbors do not share in any economic gain that the quarry enjoys, but they are forced, without their consent, to suffer the detriments. The negative conditions experienced by residents close to quarries everywhere is such a universal problem, and it is so significant, that the Bureau of Mines, in its highly regarded and often cited Report Investigation 8507, states: “Neighbors around the mining operations and other blasting… require protection of their property and health so that they do not bear an unreasonable personal cost.” (Bureau of Mines, RI 8507) The threat of flyrock will increase safety hazards for nearby residents, travelers, and workers. • The 200 and 275 ft setbacks are dangerously small for blasting. • The setbacks are not even the distance of a football field. • The region’s unstable underlying soils require greater blasting distances to ensure safety. • The MSHA recommends a 2400-foot setback for quarries that have experienced flyrock that traveled 1600 feet (like this quarry did in 2014). The proposed mining area is only about 1100 feet. • The National Mining Association (NMA) recommends a minimum 500-foot setback [before adjustments are made for previous accidents or soil conditions]. The proposed mining area is small and “tight” for a mining area. • It is bounded on 3 sides by sensitive receptors (homes, public roads, chemical storage, human life, pets). • The area is only about 900 by 1100 feet, not leaving enough room to contain flyrock or mitigate impacts. • The area's geological conditions significantly increase the likelihood of uncontrolled flyrock incidents. (More on this topic on pages below) Public safety commitments will be violated: Allowing blasting south of the San Diego River violates Resolution R-258660, which requires that mining operations “not adversely affect the neighborhood, the General Plan, or Community Plans, and not be detrimental to the health, safety, and general welfare of persons living or working in the area.” Blasting on the south side of the SD River is different than blasting on the north side of the SD River: The area described in Condition #10 is on the SOUTH side of the San Diego River. To date, all blasting under this CUP has been done on the NORTH side of the San Diego River. THE NORTH SIDE (Current blasting): • Blasting has been done here for many years. • Expansive area allows room for blasting. • There is OPEN SPACE on 3 sides of the blasting area. If something goes wrong with the blasting, there is the safety factor of distance built in on these sides THE SOUTH SIDE (Condition #10 blasting): • “TIGHT” area, only 275 feet from homes and 200 feet from a major highway. • There is not room for the set-back distances recommended by the Mine Safety and Health Administration (MSHA). • There is open space on ONLY ONE side of the blasting area. If something goes wrong, homes are on two sides, public roads are on two sides, and a production area for asphalt with stored toxic and flammable substances is on the third side. 
Condition #10 would bring blasting significantly closer to homes in Allied Gardens and Mariposa.
Moving blasting closer to homes contradicts the CUP’s intent to protect public health, safety, and welfare. Vibrations, both in ground and through the air: • Can literally shake the house. • Are annoying at best. • Are frequently frightening. • Are a very real cause of damage. The 1980 U.S. Bureau of Mines Report 8507 is a frequently used guideline. (Siskind et al.)
However, experts challenge the limited interpretation of Report 8507. • Many experts argue that the report’s conclusions are often misapplied. Factors such as repeated blasting, soil conditions, building materials, and structural vulnerabilities can contribute to damage even when vibration levels remain below the stated threshold. • Threshold damage is not readily visible to the homeowner and often requires the use of special lighting and magnifying lenses to be seen. (Heidelberg Materials, www.heidelbergmaerials.us, viewed 2-11-2025) • The probability of damage to a home may be relatively small in any single blasting event. However, the more times a home is subjected to blasting, the more opportunities there are for damage, and ultimately it is likely that some damage will occur. (Dr. Sam Kiger, University of Missouri, Miller Paving Ltd. v. McNab/Braeside (Township)) It’s like a lottery ticket. You may have 5 % chance of winning with one ticket. If you buy 20 tickets, your chances are a lot higher. So it is with blasting. The more you “play,” the higher your chances of “winning.” • All homes have natural changes (such as, sometimes a door sticks, other times it does not). Existing natural stresses can combine with the stresses from blasting to put a strain on the house that can cause damage beyond what would be caused by blasting alone. (Kiger) Once there is damage, even very slight damage, it is much easier for that damage to expand with further blasting. (For example, consider how sturdy a windshield is. But once it gets even the slightest ding or crack, it takes very little extra stress for the crack to rapidly expand. Once the structural integrity of an object is damaged, even very slightly, it is much easier for that slight damage to grow. (Kiger) • “Thus, even low levels of repeated occurrences of blast-induced ground vibrations can cause significant damage to a home over time.” (Kiger, Fontaina Scott v. Mountaineer Grading Co.) and (Heidelberg Materials, www.heidelbergmaerials.us, viewed 2-11-2025) • The damage threshold values can vary with the type of construction or can result from the distance the vibration is traveling. Long blast-to-residence distances can be more damaging than short distances. (vibrationmonitoringcourse.com) Vibrations have at times been very strongly felt by residents of Allied Gardens and San Carlos, even though blasting under CUP 82-0611 at the Mission Gorge quarry has only been done north of the San Diego River. (Correspondence of the City, the Facility and the Community, March 2024) When strong vibrations are felt, residents are often terrified. Moving the blasting even closer to residences is NOT in keeping with the intent of the CUP process that “Each use be developed so as to fully protect the public health, safety, and welfare of the community.” (SDMC 126.0301) Soils beneath the Proposed Mining area show unsafe conditions.
The map below shows the different subsoils in the blasting areas. Their characteristics are listed below. 
California Dept of Conservation, Special Report 217
Unsafe subsoils underlie the proposed mining area in condition #10, creating hazardous blasting conditions. These subsoils are unsuitable for blasting, as they have previously caused flyrock, rockslides and resulting slope instability—risks that could recur, along with the potential for liquefaction. (All information, except as noted, is taken from the California Department of Conservation.) Characteristics of subsoils in the Proposed mining area (Condition #10) Qval : • May have significant clay content. [The flyrock incident of 2014 was composed of clay that was hidden within rock.] (MSHA citation # 8698481) • Susceptible to liquefaction • Can pose stability issues Tss : Generally stable as bedrock, however: • May have weathered zones or fractures • May experience rockfall hazards • May pose secondary hazards to nearby infrastructure in areas with active faults Characteristics of subsoils in the current blasting area (where the flyrock incident of 2014 originated): pKm, predominantly: • May have faults or fractures • May have potential zones of weakness • May pose landslide risks on steep slopes • This is the area where the flyrock incident of 2014 originated. Tss: Generally stable as bedrock, however: • May have weathered zones or fractures • May experience rockfall hazards • May pose secondary hazards to nearby infrastructure in areas with active faults Characteristics of subsoils in the area underlying asphalt and concrete plants Qya: Loose sediments deposited by rivers and streams, typically including sands, gravels, silts, and clays • Prone to liquefaction • Subject to erosion, settlement, and differential compaction • Potentially unstable for construction without proper ground improvement The Mission Gorge Fault The Mission Gorge Fault runs more or less parallel to Mission Gorge Road and crosses into the CUP area about where the concrete and asphalt plants are. While the fault is not listed as active, all fault lines, even inactive ones, are surrounded by loose rocks from previous activity. These loose rocks can pose a danger during seismic activity. Information from the initial environmental study done in 1983: “The project site is rated BC and C, indicating the potential for unstable geological soils conditions” with: 1) potential slope instability and slide-prone formations; and 2) liquefaction of loosely consolidated alluvium in the San Diego floodplain. 3) The seismic study also locates an off-site concealed fault paralleling the property and following Mission Gorge Road. (Initial Study, EQD No. 82-0611, 1983) The Takeaway regarding subsoils underlying the Condition #10 blasting area: The soils under the quarry have been known to be problematic since the environmental study in 1983. (Initial Study, EQD No. 82-0611, 1983) with confirmation by the 2012 California Department of Conservation Special Report 217. The high clay content and fractures in the rock beneath the Mission Gorge quarry, especially in the proposed new mining area, increase the risks of:
WHAT OTHERS SAY The U.S. Bureau of Mines says this: "Neighbors around the mining operations and other blasting... require protection of their property and health so that they do not bear an unreasonable personal cost" (RI 8507) The San Diego General Plan says this: “Produce sand and gravel with minimal harm and disturbance to adjacent property and communities.” (CE-K.3, 2024) San Diego Municipal Code says this: The Intent of the CUP process is that: “Each use be developed so as to fully protect the public health, safety, and welfare of the community.” (SDMC 126.0301) The California Legislature says this: Major consideration will be given “to preventing environmental damage, while providing a decent home and satisfying living environment for every Californian.” (PRC, Division 13, Chapter 1. Policy 21000 (g)) Consider this: A company does not have the right to diminish the utility and value of nearby homes under any circumstances. It is especially unjust if the company will enjoy increased profits because of such practices while the neighbors neither participate in these profits nor receive financial compensation for their loss. The National Mining Association (NMA) says: The minimum safe distance for employees of blasting companies is 500 feet from the blast site. This does not include extra distance to mitigate problems such as flyrock. Presumably non-employees (such as residents) are afforded the same protection as employees. (NMA, COREsafety initiative) The NMA is an association of companies in the mining industries. It is NOT a government organization. This is what the mining companies themselves are recommending. (Vulcan Materials Company is a member of NMA!) The Federal Mine Safety and Health Administration (MSHA) reports: In 2014, the Mission Gorge Mine experienced flyrock traveling 1600 feet. The flyrock incident involved clay that was hidden within the hard rock being forcefully propelled in an uncontrolled blasted. (MSHA citation # 8698481) The MSHA also says: The set-back for blasting in a mine that has experienced a flyrock incident should be a minimum of 1.5 times the distance that the flyrock was thrown, (https://www.msha.gov/mnm-serious-accident-alert-surface-blasting) (www.msha.gov) Per the MSHA best practices: The set-back for blasting should now be 2,400 feet (1600 feet times 1.5), not the distances set in 1983, before any flyrock incident was reported. (https://www.msha.gov/mnm-serious-accident-alert-surface-blasting) Blasting experts say: Areas like the proposed mining area are “tight” and problematic. (Mankato Free Press, 10/21/2017) The area is narrow and closely bounded by sensitive receptors on 3 sides: • To the east, a public road and a residential community. • To the south, a major highway and regional bicycle path which is adjacent to a residential community. • To the west, the facility’s production area, which includes the asphalt plant and storage of: - 60,000 gallons of asphaltic oil stored in heated above-ground storage tanks (p. 15), - Up to 500 tons of finished asphaltic concrete (p. 15), - 5,000 gallons of concrete admixtures (p. 11), - 6,000-12,00 gallons Diesel fuel stored in above ground storage tanks (p.18). - 6,800 gallons of diesel fuel per single truck delivery (p. 18), (SWPPP, WDID No.: 9 371005157, 2015) Mining operators might argue: "We can adjust the amount of explosives, the blasting design, the sequencing of ignition for blasting holes and we can tell the blaster and the driller to be in constant communication. Thereby we will avoid flyrock. However, flyrock continues to be a problem. (MSHA citation # 8698481, Event Number 6595381, mine ID 04-00089) But Experts say: If the mining operation is so fastidiously careful and the blasting area is so limited, and the amount of explosives used is so small as to virtually guarantee that no flyrock could possibly escape the blasting area, the operation would be so expensive that there would be no profits at all. (Jack Eloranta, ISEE, 2017) The truth about human nature: No matter how many safeguards are in place, there is absolutely no way to 100% prevent human error. The truth about the nature of blasting: BLASTING IS ALWAYS DANGEROUS. Safety must always be the first and primary concern. (30 CFR § 56.1) The truth about flyrock: It is totally unpredictable. Its path is totally unpredictable. It can travel up to 400 miles per hour. It can be as large as a car or as small as marbles. Flyrock is the primary cause of accidents for open-pit mines. A quarry that has had an occurrence of flyrock is more likely to have another occurrence. Any flyrock incident is considered serious. The flyrock that occurred at the Mission Gorge quarry in 2014 traveled further than most flyrock travels. (Trivedi, Singh and Raina,2014) Regional regulations for blasting setbacks: Regional regulations usually do not give absolute distances for blasting set-backs as each operation is supposed to evaluate its unique situation and design blasting areas accordingly. However, the NMA, as mentioned above, has determined that the blasting area must be at least 500 feet; and the MSHA has a best practice that the set-back for a quarry that has had a flyrock incident should be a minimum of 1.5 times the distance that the flyrock traveled. Other areas are starting to mandate minimum set-backs. Setbacks in other places:
Flyrock Is Inevitable Wherever Rock Is Blasted Excerpts from the 2019 Worker’s Hazard Alert Issued by the National Institute for Occupational Safety and Health (NIOSH) · Flyrock can still be generated even in the best-designed blast
(Current developments in quarry blasting ‐ e‐library WCL. 2015) · Flyrock can never be completely eliminated. (Surface mineral workings: control of blasting, 2000) · The detrimental effects of flyrock are unavoidable and cannot be completely eliminated. (Ghasemi et al, 2012) · Flyrock is a hazard that operators try to minimize but is always present. (Ormerod, 2019) · Flyrock is an undesirable phenomenon in the blasting operation of open pit mines. (Amini, et al, 2011) · Danger and damage from flyrock in rock blasting has been a serious problem ever since blasting was introduced. Not only have men been killed and injured but also buildings, equipment and materials have been damaged. (Lundborg et al. 1975) · The phenomena of flyrock are always uncontrolled and can never be brought down to zero. (Singh, eta al, 2014) · Flyrock due to blasting in opencast mines is complex in nature as it is a random phenomenon. · “You can never say never.” No matter how careful a blaster is there is no certainty a blast will not cause flyrock. (Tim Rath, Green Mountain Explosives, Testimony at Rivers Quarry Application Hearing) · [The] blasting expert cannot guarantee that flyrock will not leave the Rivers parcel, regardless of what precautions are taken to minimize the risk. (Cross Exam of Rath 12/15/2008) · Every borehole is a separate detonation. This means that during every blast event (at the proposed Rivers’ quarry) there would be 62 chances for flyrock from face burst, cratering, or stemming ejection. After every event, there will be an additional ten seconds or so when flyrock could rain down on neighboring homes, properties and Route 100B that could result in property damages, injury, or even death. (Testimony of Art Hendrickson on 12/15/2008, para. 110) · Flyrock is a potential hazard anytime and anywhere there is blasting. (MSHA, 2016) · Blasting is not an exact science. (Scott Parker, expert blaster testifying on behalf of Director of Occupational Health and Safety, para. 23) (Flyrock 20) · Mining and quarrying are high-risk activities. Misfires and fly rock are common hazards associated with shot firing [blasting] activities, which are routinely undertaken in these industries. (WorkSafe Victoria safety alert published September 7, 2020) |
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Regulations Pertaining to this report: The U.S. Bureau of Mines: "Neighbors around the mining operations and other blasting... require protection of their property and health so that they do not bear an unreasonable personal cost" (RI 8507) The San Diego General Plan: “Produce sand and gravel with minimal harm and disturbance to adjacent property and communities.” (CE-K.3, 2024) San Diego Municipal Code: The Intent of the CUP process is that: “Each use be developed so as to fully protect the public health, safety, and welfare of the community.” (SDMC 126.0301) The California Legislature: Major consideration will be given “to preventing environmental damage, while providing a decent home and satisfying living environment for every Californian.” (PRC, Division 13, Chapter 1. Policy 21000 (g)) The National Mining Association: The minimum safe distance for employees of blasting companies is 500 feet from the blast site. Presumably non-employees (such as residents) are afforded the same protection. (NMA, COREsafety initiative) The Federal Mine Safety and Health Administration (MSHA): In 2014, the Mission Gorge Mine experienced flyrock traveling 1600 feet. The flyrock incident was caused by clay that was hidden within the hard rock that was being blasted. (MSHA citation # 8698481) The MSHA best practices: The set-back for blasting in a mine that has experienced a flyrock incident should be a minimum of 1.5 times the distance that the flyrock was thrown, (https://www.msha.gov/mnm-serious-accident-alert-surface-blasting) (www.msha.gov) The set-back for blasting should now be 2,400 feet (1600 feet times 1.5), not the levels set in 1983, before any flyrock incident was reported. (https://www.msha.gov/mnm-serious-accident-alert-surface-blasting) Regional regulations for blasting setbacks: Regional regulations usually do not give absolute distances for blasting set-backs as each operation is supposed to evaluate its unique situation and design blasting areas accordingly. • However, the NMA, as mentioned above, has determined that the blasting area must be at least 500 feet. • The MSHA, as mentioned above, has a best practice that the set-back for a quarry that has had a flyrock incident should be a minimum of 1.5 times the distance that the flyrock traveled.
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