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The pink shaded areas are considered "moderately likely" to have asbestos in the soil. This is a detail from a new map of eastern Sacramento County produced by the state Department of Conservation.

Study finds much of Murieta is 'moderately likely' to have asbestos in its soil

Published Sunday, July 16, 2006

A new study says much of Murieta North is "moderately likely" to have naturally occurring asbestos in its soil.

Officials came to Rancho Murieta Tuesday to answer residents' questions after the release of the study and map.

The map, which officials said is accurate to within about 1,000 feet, also includes a small section of Murieta South as "moderately likely." The study does not mean the designated areas have asbestos. There are three categories of likelihood – most likely, moderately likely and least likely.

"In this area we realize that NOA (naturally occurring asbestos) occurrences are small and that they are irregularly distributed," Larry Greene, executive director and air pollution control officer for the Sacramento Metropolitan Air Quality Management District told the audience of about a dozen people. "The only way you can really tell if you have asbestos or not is to do a sample of that particular place."

Greene said his agency adopted what amounts to a zero-tolerance standard after asbestos was found during routine testing of a proposed school site in Folsom in 2004. The policy developed as a response to health concerns voiced by the public, and it addressed the amount of construction going on in Folsom and throughout the county.

"With so much building going on, we believe that the safe thing to do is to say, you've got asbestos unless you test out," Greene said.

Prior to the finding in Folsom, Sacramento County was thought to be one of the few counties that didn't have areas of naturally occurring asbestos. Greene said 44 of California's 58 counties have naturally occurring asbestos within their boundaries.

Greene described the levels of asbestos that have been found in Sacramento County as "very low. These are not the high levels you see in El Dorado County."

The study and map are available for download here.

Asbestos is the term used for fibrous minerals found in certain kinds of rock. The fibers pose a health risk when they're released from the rocks by crushing or a weathering process.

Serious diseases can occur when someone breathes air that includes asbestos fibers. All forms of asbestos fibers can cause cancer and are classified as carcinogens.

"Asbestos is a risk when it's airborne. When it's in the ground, no problem. If it's not in a situation where it gets up in the air, it's no problem," Greene explained.

According to the study, the map is based on information "compiled and interpreted from published and unpublished geologic maps. … Limited fieldwork was conducted to check the accuracy of the geologic maps used." A disclaimer states the presence or absence of asbestos can only be determined through "a detailed site-specific examination of the property."

The study and map were prepared by the Geological Survey division of the state Department of Conservation and the map covers the eastern area of Sacramento County.

Senior geologist Chris Higgins, co-author of the study, told the audience the map interprets existing geological information to show "the relative likelihood for the presence of NOA."

Higgins explained that the study's three categories characterizing the likelihood of finding asbestos in an area were determined by the presence of certain types of rocks in settings that facilitate the formation of asbestos.

According to the report, "the presence of asbestos in nature is related to the chemistry of rocks in an area and the different geologic processes that have acted on those rocks through time. … The geology of eastern Sacramento County is characterized by a variety of igneous, metamorphic, and sedimentary rocks, some of which have been faulted or sheared. The geologic diversity in eastern Sacramento County provides some settings that are favorable for the presence of NOA."

Parts of Rancho Murieta that contain these settings and rocks come under the "moderately likely" category of the report.

The most likely areas for NOA have ultramafic rock and serpentinite, the rock types most commonly associated with asbestos. These rock types are known to exist in Placer and El Dorado counties, but they have not been found in eastern Sacramento County.

The purpose of the map is "to aid cities, counties, special districts, and state agencies in determining where they may wish to consider actions to minimize generation of and exposure to dust." This was Greene's message at the meeting.

"We aren't health officials. … We are the people who go out and make sure people … don't create dust," he told the group.

There are existing regulations to control dust at construction sites and quarrying operations like the three proposed north of Rancho Murieta along Scott Road.

"Areas that don't have asbestos still have to do normal dust control. We're doing that just to keep dust down across the whole county," Greene said, adding that the agency has 12 inspectors who monitor compliance.

Dust-generating activities are subject to controls and a formal dust mitigation plan is required for construction involving more than one acre, the officials said.

The presence of naturally occurring asbestos escalates those dust controls to a higher level mandated by the California Air Resources Board under the Airborne Toxic Control Measure.

The areas in Rancho Murieta that have been designated as likely to have naturally occurring asbestos are subject to this measure. "You've got asbestos unless you test out," said Greene. Testing requires three samples per acre.

The Airborne Toxic Control Measure mandates watering down areas that are being excavated or graded, preventing "track-out" by keeping soil on the site and off the pavement, and covering the completed construction area with three inches of soil or an acceptable alternative. "We've found out that that process has worked pretty well in Folsom," said Greene.

Some developers decide not to test every acre of a project. Instead, they upgrade their dust mitigation plan to carry out the provisions of the control measure for asbestos, Greene said. "They don't have to test. They do have to remediate."

If testing confirms the presence of asbestos, the toxic control measure applies.

Developers aren't the only ones who have to deal with the asbestos issue. Anyone within the areas identified as likely to contain naturally occurring asbestos is subject to the same constraints regarding activities that create dust.

"This is particularly important if someone's doing a pool," said Greene. In addition to the dust issues during construction, there's a soil disposal issue. Depending on test results for asbestos, the soil might have to be treated as a hazardous waste.

Contractors are informed about what's required at sites where asbestos may be present as part of the permitting process, officials said.

In response to a question about the proposed quarrying operations that have property within the likely NOA areas, Greene said, "We've already notified them of this determination. … They have a specific Air Toxic Control Measure that applies just to mining."

The proposed elementary school site on Stonehouse Road is part of the area designated on the map as "least likely" to have naturally occurring asbestos. In addition, the area was tested and cleared as part of the site evaluation process conducted by the Elk Grove Unified School District.

More information about naturally occurring asbestos, including health facts and ways to minimize exposure, is available here.

Dust and air quality complaints can be made to the Sacramento Metropolitan Air Quality Management District at 874-4800.

Paper versions of the map and study are available for viewing at the CSD and the Rancho Murieta Association.