NOA Air-Quality Lessons Learned during Calaveras Dam Replacement Project BART EKLUND* AECOM Corporation, 9400 Amberglen Boulevard, Austin, TX 78729
JOHN ROADIFER NOEL WONG MICHAEL FORREST AECOM Corporation, Kaiser Center, 300 Lakeside Drive, Oakland, CA 94612
Key Terms: NOA, Asbestos, Air Quality, Emission Controls ABSTRACT The Calaveras Dam Replacement Project (CDRP) pioneered technical approaches for addressing community exposure to naturally occurring asbestos (NOA) via the inhalation pathway. Over the course of the CDRP, approaches were developed for key issues, including determining the NOA particles of interest, defining the toxicity limits to apply to various types of NOA particles, establishing dust control, and creating appropriate feedback loops for using laboratory data. Specific issues of interest included whether to count only structures above a certain length and the inhalation unit risk value to use for amphiboles. The knowledge gained on the CDRP can and is being used to optimize NOA evaluation and control at other, similar projects. INTRODUCTION The original Calaveras Dam was constructed in 1925 in Alameda County, CA. At the time, it was the largest earth-fill dam in the world. The resulting reservoir was situated primarily in Santa Clara County and had a capacity of 100,000 acre-ft (120 million m3 ) and a surface area of approximately 1,450 acres (590 ha). It was determined that the hydraulic fill dam was subject to liquefaction failure during seismic activity, and the capacity of the reservoir was restricted to approximately 40 percent capacity by California regulators in 2001. To restore lost capacity, the San Francisco Public Utilities Commission (SFPUC) constructed a replacement dam located approximately 1,000 ft (300 m) downstream of the original dam. This was called the Calaveras Dam Replacement Project (CDRP). * Corresponding author email: bart.eklund@aecom.com
Construction on the new earth- and rock-fill dam began in August 2011, and construction activities were completed in late 2018. The new dam is 220 ft (67 m) high and 1,180 ft (360 m) wide at the base. The volume of the dam is 3.5 million yd3 (2.7 million m3 ). About 11 million yd3 (8.4 million m3 ) of material was excavated during construction, some of which contained naturally occurring asbestos (NOA). A broad definition of NOA was applied (i.e., California Air Resources Board Asbestos Hazard Emergency Response Act [CARB-AHERA] structures), as discussed later in this paper.
Air-Quality Program A comprehensive air-quality program was undertaken to address species of interest. Pre-construction air monitoring was performed to develop a baseline of local air quality. Twenty-four-hour, time-integrated samples generally were collected on a monthly basis. In total, 22 monthly monitoring events were performed from August 2008 through December 2009 and from May 2010 through November 2010. Routine air monitoring began in January 2012 and continued through November 2018. The work was done in compliance with a Comprehensive Air Monitoring Program (CAMP) document that served as the test plan (URS, 2012). The CAMP document was amended about a dozen times between October 2013 and December 2016 as new information became available and the results-to-date were reviewed and evaluated. The dam construction took place in a valley that primarily ran north-south. There were relatively few residents located within 5 mi (8 km) of the construction activities in either direction, but the largest number of potential receptors was to the north. The monitoring network included six community monitoring locations located to the north over an extended distance, and
Environmental & Engineering Geoscience, Vol. XXVI, No. 1, February 2020, pp. 35–38
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