SERPENTINE ROCK INFORMATION
March 12, 1994
This information was prepared to respond to possible homeowner questions about serpentine rock which may be present below the soil surface at the Silver Creek Valley Country Club. In summary: It is unlikely that a homeowner will encounter serpentine rock in surface soils at the Silver Creek Valley Country Club. Keeping serpentine rock wet and minimizing airborne dust have been used as simple and effective methods to control possible asbestos released from serpentine rock during construction activities.
What is serpentine?
Serpentine rock is a hard, greenish/gray rock which contains naturally occurring asbestos veins embedded in the rock, Serpentine rock is very common in California. In fact, serpentine rock is the State of California designated "state rock". Typical serpentine rock contains less than 1-5% asbestos. The asbestos in serpentine is not generally free to be released unless the materials is mechanically disturbed by methods such as crushing or grinding.
Serpentine contains a form of asbestos called chrysotile. Chrysotile asbestos is the most common form of asbestos and is regarded by some scientists to be the least hazardous form of asbestos. Chrysotile asbestos is present in our cars' brake linings, in many building products installed before 1980, and in commercial products such as felts, friction products and millboard. The ambient air that we breathe and the water we drink contain background concentrations of asbestos because asbestos is a naturally occurring material in the ground. Also present day uses of asbestos, such as in car brake linings, release asbestos into the environment.
Could Serpentine be present on my Silver Creek Valley Country Club Lot?
Serpentine is common in the San Jose, California area. Shea Homes has covered all identified serpentine within all Residence building pads with a two-foot thick layer of non-asbestos laden material. However, the possibility exists that any excavation may encounter some serpentine material. The Silver Creek Valley Country Club development was carefully managed for the safety of future homeowners. Geologists and environmental consultants worked with Shea Homes to minimize the potential for future handling of serpentine material.
Is the asbestos in serpentine hazardous?
Asbestos in serpentine is embedded in the rock. Asbestos is not hazardous unless it is somehow released from the rock, becomes airborne in higher concentrations than normal background concentrations and is inhaled in some quantity. It is difficult to release the asbestos from serpentine rock because the rock is very hard. Power tools such as jackhammers and pulverizers, which violently disturb serpentine rock, are capable of releasing asbestos from serpentine rock.
The State of California regulates asbestos, in the workplace and the environment, as a material known to cause cancer. These regulations only apply to long asbestos fibers (greater than 5 microns in length) which are rarely released to the air when serpentine rock is disturbed. When serpentine rock is broken up by digging activities, the asbestos fibers which may be released are generally very short in length (less than 5 microns in length).
The State of California regulations for asbestos also specify airborne concentrations of asbestos which may not be exceeded without special notifications or control measures. Extensive air monitoring and soil testing has been conducted during the excavation and grading of serpentine rock at the Silver Creek Valley Country Club. The results show that occupational and environmental criteria are easily met using some fairly simple control methods such as keeping the serpentine material wet during construction activities.
Non-occupational exposures, such as digging in serpentine-containing soil, have generally not caused asbestos-related diseases due to: the infrequency of exposure; the much lower airborne concentrations present: and the forms of asbestos encountered. Nevertheless, since asbestos is a carcinogen, it is a good idea to minimize exposure whenever possible.
What do l have to do when I want to landscape or put in a pool?
Serpentine may not be present in the area of your home or the area of your planned work. If your planned work may expose or disturb any soil which is more than two (2) feet beneath the grade, refer to the CC&R's for requirements when performing this work.
Should I be concerned if my neighbor is digging in his yard and causing dust to blow towards my house?
Most surface soils at the Silver Creek Valley Country Club do not contain serpentine. So airborne dust from a neighbor is likely to be more of a housekeeping and nuisance concern than a health concern.
If a neighbor is digging in serpentine material and causing airborne dust to blow towards your house please, request your neighbor to control the dust. Keep in mind that non-occupational exposures, such as digging in serpentine-containing soil, have generally not caused asbestos-related diseases. This is due to the infrequency of exposure, the much lower airborne concentrations present and the less hazardous form of asbestos encountered.
What do I have to do with excavated soil?
The transportation and disposal of asbestos-containing materials is covered by state and federal regulations. If your work produced excess dirt from more than two (2) feet below grade, then consultation with an environmental professional should occur before moving potential asbestos-containing materials from your property. You may contact either David Durst or Bruce Keyston at McLaren/Hart, (916) 638-3696, for a current recommendation.
It is unlikely that a homeowner will encounter serpentine rock in surface soils at the Silver Creek Valley Country Club. Keeping serpentine rock wet and minimizing airborne dust have been used as simple and effective methods to control possible asbestos released from serpentine rock during construction activities.
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