Proposed Oster/Las Pilitas (Hwy 58) Rock Quarry





The proposed Las Pilitas Quarry, also publicly known as the Oster Quarry and the Hwy 58 Quarry, presents impacts to the community both positive and negative.  The proposed quarry would provide five new jobs on site and may create increased competition for DG & granite products.  Profits from the quarry might be realized by local owners if the current applicants retain ownership.  It would seem that there would be additional jobs for truckers but that is drawn into question by this statement in the original applicant provided traffic study:  "The project is contending that it's own operations will likely remove Hanson trucks while replacing those with project trucks, resulting in a net balance of current quarry related traffic."  If proposed operations only take away existing business, would there be any additional revenue to the county of San Luis Obispo?
Impacts on local aesthetics, agricultural resources, air quality, biological resources, cultural resources, geology and soils, hazards and hazardous materials, noise, population/housing, public services/utilities, transportation/circulation, water, land use, environmental justice, groundwater contamination, surface water contamination, vibration, dangerous precedents, expanded operation and losing local control are explored below.

Blasting photo

Quarry blasting introduces a wide range of impacts


  • Project will change the visual character of the area forever. 
  • In the SLO County Open Space Element Table VR-2 Hwy 58 from the Santa Margarita Urban Reserve Line to the Kern County line is a candidate for a scenic corridor.
  • View from many locations along Hwy 58 will be impacted.
  • View from 101 corridor will be impacted.  
  • Project is adjacent to a 1914 “Scenic Historic Bridge”     
1914 Salinas River truss bridge
The Salinas River is a rich wildlife corridor and regionally important waterway.

Looking east on Hwy. 58 from approximately post mile 4.45.

White area is the project applicant's representation of the area of visual impact from this specific location only. The accuracy of this simulation is yet to be verified by consultants and planners.  The affected area will also be visible from numerous other corridors, with less obstructions the higher the viewing elevation is.  


  • This project may impair agricultural use of other properties.
  • Blasting is known to be a disturbance to livestock and domestic animals.
  • Dust and air contaminants can affect agricultural production.


  • Greenhouse Gas Emissions-Removing vegetation from a site this large provides sufficient reason to study this. Vegetation absorbs carbon dioxide. How will this loss be mitigated (compensated for) and what monitoring (enforcement mechanism) will be in place?
  • Will the perimeter of the site be monitored for PM10, PM 2.5, and the presence of Crystalline Silica? Many modern quarries require constant monitoring samples. Particulate matters are known to cause respiratory illnesses, lung damage, and be particularly hard for those with asthma to tolerate. Crystalline Silica is known to cause Silicosis. Blasting rock creates respirable fractured crystalline silica and is not visible, but is caught in the lungs forever.  Over a million google results for silicosis  
  • Valley Fever is known to occur in this area and a recent report states that cases are on the rise in the county. How will this increased risk due to soil disturbance be addressed?  Valley Fever Facts
  • The application states that portable crushing and screening will be used as needed. NOTE: Portable crushers are not usually enclosed. How will dust from these operations be contained?
  • Will quarry processing equipment be fully enclosed to minimize dust and fugitive dust?
  • This site does not have the buffers that the other existing quarries near Santa Margarita have built in due to their siting.
  • At what wind speed will quarry operations cease?
  • How will wind speed restrictions be monitored and enforced?
  • It is dangerous to fill holes with explosives and then not detonate them.  What happens when explosives are placed but not yet detonated before wind speeds increase to unacceptable levels? 
  • What measures will be taken to mitigate dust during transportation?
  • Will there be any way to monitor and enforce this?
  • Do the truck trips proposed include the delivery of additional hazardous materials for plant operations?


  • Quarrying/mining operations are known to result in a loss of unique and special status species because of their destructive nature.
  • Applicant states in Initial Study that avoidance will be their mitigation technique.
  • Will it be possible to monitor and enforce avoidance of certain species of plants and wildlife?
  • This project is on property the  Salinas River flows through.  Will wetland or riparian habitat be impacted?
  • Biological studies should be conducted at the proper time of year and for appropriate duration to be meaningful. Several months are required, usually April to August.  October/November were utilized in the applicant commissioned studies.  


  • Project area is known to be rich with cultural history.
  • It does not appear that any attempt to contact Native American representatives has ever been made.
  • The disturbance of cultural resources should not be limited to the immediate area being mined. It needs to encompass the entirety of areas that are incidentally affected by quarrying.  Disturbed areas will have a far greater reach than just the proposed extraction area.  Among these will be the proposed turnout lane, and the numerous staging areas.  
  • It is believed that the historic workers camp for the Salinas Reservoir Dam project built in the 1940’s was located in this vicinity. This does not appear to be part of the Cultural Resources Study.


  • Don't we need economic development in this area?
    Of course we do!!  But large-scale industrial mining isn't development, it's EXPLOITATION!!
    Industrial mining brings no significant economic benefits to a community--it's a highly automated industry with virtually no fixed plant, so we can expect few new jobs (applicant estimates 5), and little additional tax revenue.  What we can expect is noise, vibration, dust, traffic, road degradation, visual impacts, declining property values....... and more mines if this one successfully penetrates zoning and infrastructure constraints.   
  • Working people in the area depend upon a stable residential community to remain prosperous.  While excessive quarrying might be beneficial for a few quarry owners, the rest of us will suffer the effects. 
  • The majority of community businesses depend on consumers for their livelihood.  When home values plummet, and homeowners abandon the area, there is no longer a customer base for the general and convenience stores, gas stations, propane vendors, restaurants, antique shops, gift shops, landscapers, lumberyards, feed stores, landlords, firewood vendors, pubs, nurseries, realtors, service provider, etc..  
  • What do WE receive in exchange for the destruction of our residential tax revenue base, our desireable rural character, and future livability of our community?  


  • Modifying topography by removing material to new unexposed layers will possibly cause erosion, unstable soil condition, and changes in drainage and surface run-off characteristics.


  • Blasting will be part of the plant’s normal operating cycle.
  • Blasting and heavy equipment present a heightened fire danger.
  • The transportation of hazardous explosives to the project site present heightened safety considerations. 
  • On-site fuel storage has been removed from the application. Are the truck trips associated with transporting fuel considered?
  • There are no proper turnouts, or road shoulders, or ways to skirt dense truck traffic on Hwy 58. How will emergency response vehicles get by large trucks and the other traffic caught behind the truck traffic? Cal Fire emergency vehicles from Park Hill Road Station respond on a regular basis to incidents West of the project site. Their response time could be greatly impacted by the project created traffic issues.
  • The State Water Project runs through the project site. Where is it located in relationship to operations and incidental operations? 
  • What potential impacts exist?  Does blasting near this line create any potential hazards? Has Department of Water Resources been made aware of the existence of this project?
  • Do repeated truck trips over the above mentioned lines create any potential hazards?
  • As mentioned in air quality, PM’s and crystalline silica are known to cause severe health hazards. Many have shared that the prevailing wind direction is almost straight up Parkhill Rd. from the quarry site.


  • What will noise levels do to the quality of life for area residents?
  • What will the operating hours be? Will Saturdays, Sundays, and holidays be part of that schedule?  Night-time hours?
  • Will any form of noise exemption be required? How will the county monitor and enforce such an exemption?
  • Will over 200 truck trips a day (based only on quarry extraction volume) create any additional noise to residents?
  • Will the additional truck trips generated by the proposal of a concrete and asphalt recycling facility receive study?
  • This project needs to be cumulatively added to other exiting noise sources.
  • Noise Study needs to address how the noise level will change with the shifting terrain a quarry operation creates. Also needs to address the change in existing noise levels created by changing the local topography. This needs to be included in the noise analysis.
  • Varying conditions of trucks and equipment will create different noise levels. Applicant's studies assumed that only new equipment in optimum working order would be employed. That assumption needs to be re-visited. 
  • Will monitoring be in place to ensure that trucks not meeting the condition assumed for study will be prohibited?
  • Will jake brakes be allowed in the vicinity?
  • Will the "sensitive receptors" included in the applicant provided Noise Study be expanded to include the many nearby residential uses currently absent from that study?


  • Will the project affect public services such as fire protection, roads, police protection, schools?
  • Would the heightened fire danger for a large operation that includes the use of explosives and heavy machinery potentially create a need for increased fire protection to surrounding residents?
  • Would placing more than 200 truck trips a day that carry up to 80,000lbs. per load have any impact on the infrastructure of our existing road and railroad system?
  • Is the design value of the Salinas River Bridge sufficient to withstand the many loaded gravel trucks that will be crossing the 323' long bridge simultaneously?  This is a reasonably foreseeable event since project applicant has stated that trucks will be coming with asphalt and concrete to be recycled and be leaving with full loads of gravel.   Link to land use waiver  filed by Las Pilitas Resources LLC seeking exemption from current ordinance prohibiting a recycling operation. 
  • These events will need to be viewed cumulatively with all the other existing truck traffic generated by projects as well as other quarries east of the proposed project site.  


  • From page 1 of Traffic Impact Study for Las Pilitas Rock Quarry (located on hwy 58 @ Salinas River) “SR 101 interchange at El Camino Real was not analyzed in this report. It is the applicant’s opinion that the interchange will not likely experience an increase in truck trips due to the operation of the proposed project." It goes on to say there is no increase in demand for material, they will just be taking other quarry business.
  • Will the need for more material be given as a reason to allow this operation after the traffic studies that are based on "there is no increase in demand for material" have been completed?
  • If business is taken from Rocky Canyon Quarry, that is an increase in truck trips for Santa Margarita.  Rocky Canyon trucks currently do not go through Margarita, they use Santa Barbara Rd. onramp.
  • All truck trips generated by Las Pilitas/Hwy 58 Quarry will be in addition to existing Highway 58 traffic.  The existing Hanson and Rocky Canyon quarry operations do not place traffic onto Hwy. 58.
  • 200 truck trips only accounts for gravel extraction.  It also assumes extraction is at a uniform rate, meaning there will be periods when traffic volume is much higher.  Asphalt and Concrete Recycling will generate additional truck trips that are yet to be quantified and will add significantly to the daily truck trip count.  Las Pilitas Resources LLC has filed a waiver to exempt their operation from the ordinance that does not allow this use on the proposed site. 
  • On-site fuel storage has been removed from the application.  Will truck trips associated with fueling on-site equipment be added to the number of truck trips being studied?  
  • Are there any traffic concerns when you try to get over 200 gravel hauling trucks a day from Parkhill Rd. area through Santa Margarita and onto  Hwy. 101?  What about days when far more trips occur (200 is an average that assumes material will be extracted equally throughout the year which will realistically not occur)?
  • Can large trucks with trailers navigate the many dangerous curves on Hwy. 58 without the results off-tracking creating safety hazards?
   According to Caltrans, "an advisory system was created because Caltrans is prohibited from restricting the KPRA on these routes. A truck with a KPRA longer than that posted may not be able to stay in its lane. Although California Legal trucks may legally travel on advisory routes, the driver is still legally responsible for unsafe offtracking, such as crossing the centerline or driving on shoulders, curbs and sidewalks." Link to source of this information      Link to Mathematical method for determining off-tracking

  • Is there a plan for large trucks to enter and exit the tight quarry site?  Will excess truck traffic use Parkhill Rd as a turnaround? 
  • Will excess truck traffic be present in the town of Santa Margarita while waiting to be radioed in to the quarry? 
  • Will creating an endless truck depot amount to the de-facto industrialization of the rural character of Santa Margarita?
  • Is there any monitoring and/or enforcement planned on a truck limit?
  • Will there be monitoring and/or enforcement when gravel trucks shortcut through residential neighborhoods in Santa Margarita?
  • Are the 30-50 truck trips a day that already exist from an existing adjacent trucking facility going to be factored into the baseline for the  total number of trips being studied?
  • What responsibility will the county accept for property damages, or fatalities caused by the failure to properly study the traffic impacts on an already very dangerous route?
  • 65'-72'  long double gravel trucks navigating onto El Camino Real make a Rail Road crossing each trip cycle. Not enough space is available (sign indicates 50') for stopping between the tracks and El Camino Real.  


  • Project application estimates 20,000 gallons per day for water consumption.  Data used in calculations has not been presented to the community at this time.  
  • Dust control alone could use 20,000 to 40,000 gallons per day in the dry months, based on information from other quarries and the extraction volumes being applied for.  
  • Project applicants have told investors and media their products will be used in portland cement concrete.  Aggregate of this quality requires washing for cleanliness according to the Portland Cement Association, yet applicant now states that no material will be washed.  
  • Does a market exist for unwashed aggregate?  Will infrastructure costs justify the production of low quality (low priced) material?
  • Because it is standard operating practice at quarries to wash aggregate, is it reasonably foreseeable to assume that washing aggregate will occur?  
  • Will the study of the impacts created by this practice be required under CEQA guidelines?
  • How will the applicant’s statement that they “will not be washing any aggregate” be regulated?  Will on-site monitoring be employed?
  • From Initial Study: “based on available information, the proposed water source is not known to have any significant availability or quality problems.”  No evidence to substaniate this claim has been presented by the applicants.  Were any of the many surrounding residents that truck water in to get through dry years consulted?  
  • Applicant may need an appropriative water right if they plan on storing water or pumping it out of an immediate watershed.
  • How do the new water diversion regulations (from the State Water Resources Board) apply to this project?
  • It is unlawful to divert at a rate which would infringe on the rights of others.
  • How will this mine’s intense water usage affect the rest of the community's residents?
  • Will the impacts be confined only to areas surrounding the proposed site?
  • Will there be monitoring and enforcement mechanisms related to regulating set rates of water usage?


  • The zoning of surrounding properties is incorrect in the project description.  Residential Rural (RR) zoning exists to the South and East, not Rural Lands as stated.
  • The number of residences that will be affected has been misrepresented in the application.  
  • Selective mapping represents that the quarry site is only surrounded by large parcels of rural land. This is false and misleading. 
  • The impacts to residents are significant when you identify that residents actually exist on adjacent and nearby parcels.  
  • It is unacceptable, unrealistic, unreasonable, and likely unlawful to not consider that the interests of other property owners and community members be considered as equal to the interests of the applicants. Should the property rights of all parties not be considered? 
  • If you were going to buy a home in this area, would you want to know about the proposed quarry?
  • How many area home purchase or home improvement decisions have already been deferred pending resolution of this proposal?  What affect has this had on property values?
  • Will the taxes generated from Oster/Las Pilitas/Hwy 58 Quarry offset the lost revenue from the lower taxes on all the homes with reduced values in the surrounding area?
  • The quality of life, the health, the safety, and the property values of a community will all be on the decline and should be given collectively the same consideration the applicant is being given in regards to the feasibility of this project.

RURAL CHARACTER becomes Industrial Character

The blight currently showing in Santa Margarita is due to some temporary construction projects that are currently underway.  The Hwy. 58/Las Pilitas Quarry would create a permanent truck and equipment depot in and around town due to the lack of sufficient staging areas on-site.  

  • Do we want the future character of Santa Margarita to be that of a truck depot and equipment yard?
  • The temporary projects responsible for the current blight are generating only a fraction of the more than 200 daily truck trips that the Hwy 58/Las Pilitas Quarry proposal would generate.  
  • First Solar talks Trucks article


  • Would you want to live near industrial operations or have your safety compromised by heavy truck traffic on a daily basis?
    As the desirability of an area decreases, so do property values. 


  • Geographic inequity describes a situation in which the burdens of undesirable land uses are concentrated in certain neighborhoods while their benefits are received elsewhere.
  • This community already is home to two mining/quarry facilities that have reserves far in excess of what the proposed life span of this project would be. Each of these existing facilities is also located (sited) in such a way that their impacts are far less dramatic to the community.
  • The community already shoulders more than it's fair share of impacts related to extraction of resources.  Is there good reason (benefits outweigh impacts) why the community should be made to shoulder the added impacts of a third rock quarry?


  • If the proposed mine extends below the water table, it could affect wells in the surrounding area. Residue from explosives, spilled fuel, and other chemicals could seep into the ground water.     


  • In addition to carrying residue from explosives, spilled fuel, and other chemicals, runoff from the site could silt up the Salinas River and other bodies of water.  The proposed project site is within the Upper Salinas River Watershed (the Salinas River flows through the Southwest portion of parcel APN 070-141-070, one of the two parcels proposed to be mined). Upper Salinas River Watershed Action Plan   


  • The enormous explosions associated with hard rock mining have been known to crack foundations and destroy drilled wells miles away. Video of mine blasting
  • Is the applicant willing to take responsibility by reimbursing for damages when such events occur?
  • Drilling in preperation for blasting is noisy and ongoing for long periods.  
  • There are three major problems with blasting in quarries:
  1. The detonation of the explosives causes a lot of dust and debris, which is unavoidable. Much of this dust will become airborne for a very short period and settle back down to earth, but not all of it. Some of the dust, which is what is called the PM10, and smaller size remains in the air and will be carried off with the prevailing wind.
  2. The explosives are loaded into a number of holes drilled into the rock. If for any unforeseen reason there is a cavern in the underground, the hole can overfill with explosives, creating a very unsafe situation.
  3. It is possible that once the holes are filled with explosives, the winds will exceed the wind speed for blasting, but now the holes are filled with explosives. What to do? Once the holes have been filled, it is too late to remove the explosives. The only safe thing to do is detonate the explosives, even if the wind speeds are above the allowable limits, which means the dust will be leaving the quarry site.


  • Once an area starts multiple mining operations, it quickly becomes less than pristine. If this proposed industrial mine penetrates the existing zoning, others will follow the lead. Many of the parcels in this area have granite deposits.
  • Rural character will quickly deterioate into industrial character. 
  • Will the signs entering town be changed to read "gateway to granite quarries"? 


  • Once an operation like this gets permitted, there is little to prevent a mining company from vastly expanding the scope of a project, adding new operations, and sending trucks out in greater numbers.
  • There is also nothing to keep the “local” principals of this LLC from selling out to a much larger corporation that has resources to push the boundaries much further.