Tulare County, located in the heart of California, contains several small but historically significant asbestos deposits. These deposits are mostly found within the serpentine-rich regions near Porterville, where asbestos was mined and prospected in the early 20th century. The county's geology, marked by serpentine rock formations, contributed to the presence of asbestos in various locations, although none of the deposits proved commercially viable on a large scale.
Among the earliest identified asbestos deposits in Tulare County was one on the McCann Ranch, approximately 15 miles south-southeast of Porterville. This small deposit was notable primarily for being one of the first documented in the region, though its quality did not support extensive mining. Another significant site was found in the Frazier Valley area on the James Ranch, northeast of Porterville, where asbestos of fair quality was discovered but not heavily exploited. Additionally, Frazier Valley yielded some asbestos near the Tule River at coordinates 36.1806, -118.8306, around 25 miles southeast of Tulare City. These discoveries pointed to the presence of asbestos in multiple locations but lacked the quantity and quality required for sustained production (Source 1).
In the early 1900s, as industrial demand for asbestos surged due to its fire-resistant properties, the limited deposits in Tulare County gained temporary interest. High-quality asbestos commanded prices as high as $200 per ton, especially for uses requiring fireproof materials, such as theater curtains, heavy tapestries, and protective clothing. Lower-grade asbestos, which was also mined in Tulare County, found applications in products like industrial steam-packing furnace linings, insulating wall plasters, paints, and heat-resistant tiles. However, the relatively low quality of the county's asbestos restricted its use to these more utilitarian purposes, rather than weaving or finer manufacturing (Source 2).
Tulare County's asbestos deposits are primarily associated with serpentine rock, a host rock known for containing chrysotile, a common form of asbestos. Serpentine formations in the county have been mapped and studied extensively by geologists to understand asbestos distribution and its implications for land use. Today, concerns about asbestos's health risks have led to a decline in any exploration or use of these natural deposits. Areas like the McCann and James ranches remain as historical sites of early asbestos prospecting, with environmental monitoring in place to prevent potential exposure (Source 3).
By the late 20th century, recognition of asbestos's health hazards spurred widespread removal efforts in Tulare County and beyond. Many older buildings, ships, and industrial sites constructed in the 1920s and 1930s that contained asbestos have been demolished or remediated. Current safety regulations ensure that asbestos-containing materials are properly managed, particularly in regions with natural deposits like Tulare County. The California Department of Public Health and federal agencies work collaboratively to monitor and mitigate asbestos exposure risks, with particular attention to naturally occurring asbestos in historically mined areas (Source 4).
The Tulare County Asbestos Occurrence Map, developed with data from the United States Geological Survey (USGS), provides a comprehensive overview of asbestos sites in Tulare County. By exploring this map, users can view specific asbestos locations, historic site names, associated rock types, host rock data, and details about the asbestos varieties found. This tool is invaluable for researchers and the public, offering insight into Tulare County's asbestos history and its broader implications for health and safety.
The map also includes interactive features, allowing users to search for streets, towns, and other localities within Tulare County. This functionality provides easy navigation and access to information about asbestos deposits and related geological data.
Source 1: United States Geological Survey. "Mineral Resources Data System (MRDS)- Asbestos Deposits in California."
Source 2: California Department of Conservation. "Asbestos and Serpentine Rock: Occurrences and Implications in Tulare County."
Source 3: National Institute for Occupational Safety and Health (NIOSH). "Asbestos Monitoring and Environmental Safety."
Source 4: California Department of Public Health. "Managing Asbestos in Naturally Occurring Asbestos Regions of California."