Ambient Air Quality Monitoring Program - Pahrump Air Quality
The Town of Pahrump is located in the Pahrump Valley of southern Nevada (hydrographic area 162) approximately 60 miles west of Las Vegas and 60 miles east of Death Valley. Pahrump is an unincorporated town governed by a five-member, elected Town Board, a Town Manager and staff. Located in Nye County, it borders the California state line. The town promotes itself as a tourist destination, and retirees comprise the majority of the population.
The Problem: Fugitive Dust
Fast population growth in the ‘90s through mid-2006 created intensive development. Large parcels of land were cleared of vegetation, subdivided and prepared for housing construction. Dirt and gravel roads were constructed. Many of the planned housing developments never materialized and the lots are now disturbed, vacant areas.
As a result of the disturbed, vacant land and the number of dirt and gravel roads, fugitive dust (particulate matter less than 10 microns, or PM10) became a problem. The Pahrump valley is subject to high winds and these winds often create dust storms. Even the slightest wind can pick up dust from the disturbed areas, where it can become a health hazard.
Citizen complaints in the late 90's led to the installation of an ambient air monitor in the downtown area. The Nevada Bureau of Air Quality Planning (BAQP) has been monitoring for PM10 in the Town of Pahrump since January 2001. Currently, there are four PM10 monitoring stations in various locations within the town. The monitors record ambient air data continuously, which is downloaded to the BAQP office in Carson City. Once monitoring was initiated, 27 exceedances of the national 24-hour ambient air quality standard (NAAQS) were recorded during 2001, 2002 and 2003. Under the federal Clean Air Act, this meant that Pahrump was not attaining the federal PM10 24-hour health-based standard of 150 ug/m3.
Particulate Matter (PM)
Particulate matter consists of very small airborne particles, less than 10 microns in diameter. Common sources of particulate matter are: burning fuels, such as wood in woodstoves and fireplaces or diesel in motor vehicles; crushing or grinding; dust from unpaved roads and construction sites; and industrial processes. Breathing high levels of particulate matter is harmful to lung tissue and aggravates asthma symptoms. Additional information is available regarding Air Quality and Particulate Matter
After exceedances of a NAAQS are monitored and an area is deemed to be in nonattainment by the state, the Governor typically submits a letter to the US Environmental Protection Agency (US EPA) recommending that the area be designated nonattainment. US EPA then evaluates the state’s recommendation and promulgates its decision in the Federal Register. Once an area is designated nonattainment, the state has three years to prepare and submit a state implementation plan (SIP) to US EPA. The SIP will contain a strategy with specific measures to bring the area back into attainment of the standard within five years of designation. Once the standard is achieved, control measures must remain in place for at least 10 years to ensure the area does not fall back into nonattainment.
When it became clear that Pahrump was exceeding the PM10 NAAQS, the BAQP discussed a second, more informal option for resolving the problem with the US EPA and Nye County. The US EPA agreed to allow the BAQP and Nye County the opportunity to address the problem through a Memorandum of Understanding (MOU). An MOU allows significantly more local control of the process and significantly less federal involvement. However, to justify this informal approach, the BAQP and Nye County had to demonstrate to the US EPA the environmental benefit of addressing the problem through an MOU. The BAQP and Nye County had to show that this approach would be more effective and/or produce results faster.
The US EPA, the Nevada Division of Environmental Protection (NDEP), the Pahrump Town Board and Nye County agreed to use the MOU approach instead of the formal SIP submittal. The MOU was signed by all four parties in September 2003. For the purpose of the MOU, the Pahrump Regional Planning District boundaries were used to generate the emission inventories. More information on the MOU can be found in the briefing document, and in the list of definitions. The MOU established a deadline of December 31, 2009 to bring the area back into attainment. Control strategies were required to be in place by 2006 and remain in place to ensure that the Pahrump Valley continues to attain the standards in the future.
The state and local agencies are working cooperatively under the MOU to expedite air cleanup for continued public health and welfare in Pahrump. The MOU was the first step in accelerating the development and implementation of a locally-initiated PM10 control plan. As part of the effort to control dust in Pahrump, the NDEP developed and operates a PM10 monitoring network, conducted a baseline emissions inventory, evaluated dust control measures for the Pahrump Valley and identified best available control measures, as discussed below.
The NDEP identified the major sources of fugitive dust in Pahrump. Then the BAQP staff performed a survey of the Pahrump Valley. Staff compiled the 2001 base year emissions inventory including fugitive dust sources (roads, lands amp; construction), vehicles (on-road & non-road) stationary sources and fires. Based on the 2001 inventory, fugitive emissions from unpaved roads and disturbed vacant land were found to be the biggest sources of PM10 emissions, accounting for 92% of PM10 emissions in the Valley. The MOU process allowed the NDEP and Nye County to focus on controlling the sources of emissions most responsible for the exceedances of the standards.
The NDEP developed a list of potential control measures to minimize fugitive dust in the valley. The Pahrump Valley Air Quality Management; Control Measures Assessment lists some of the measures that were considered. The list was refined after meetings and briefings that included elected officials from Nye County (Board of County Commissioners), the Pahrump Town Board, and the public. Cost, effectiveness, enforceability and testing, and implementation of the various control measures were evaluated.
Finally, the impacts on PM10 concentrations of implementing the control measures were assessed. Projected future year (2009) emission inventories were used to calculate expected reductions. Based on all of this information, a suite of control measures for unpaved roads and disturbed lands was selected. These include, for example, a commitment by the County to continue it’s paving and chip sealing program, the regulation of unpaved parking lots, storage areas, construction activities, and open areas and vacant lots, as well as strict enforcement of the state fugitive dust regulations. In addition to such area-wide measures, site-specific control measures were identified to minimize PM10 concentrations during annual events such as Harvest/Fall Festivals.
Monitoring Network in Pahrump
All of the monitors in Pahrump collect data on a continuous basis and are located in conjunction with a weather station capable of measuring maximum wind speed, wind direction and temperature. Each monitor is a Beta Attenuation Monitor and is the equivalent of a federal reference method monitor. The BAQP has the capability of downloading data hourly via wireless telemetry from each of the monitors. The map of the NDEP monitoring sites shows the locations of the monitoring sites in relation to each other and also shows the location of the meteorological tower.
The BAQP has been monitoring the ambient air quality for PM10 in the Town of Pahrump since January 2001. The first monitor was installed near the municipal pool in the downtown area. Two sites were added in 2003, and by 2006 the BAQP had expanded the monitoring network in the Pahrump Valley to four sites: the Willow Creek Golf Course, the "Our Lady of the Valley” Roman Catholic Church on Gamebird Road, Manse Elementary School and a background site on Linda Street. As of fall 2010, monitors are located and operating at Linda Street, Manse Elementary School, Glenoaks Street and the church on Gamebird Road.
The NDEP’s current and historic air quality monitoring data for Pahrump can be accessed on our near real-time monitoring page.
County Commissioners Approve Air Quality Ordinance.
The Pahrump Regional Planning District Dust Control Regulations (Nye County Ordinance 289) were adopted by the Nye County Board of Commissioners on August 17, 2004, and became effective on January 1, 2005. The Nye County Air Quality Department enforces the dust control regulations for the Pahrump Regional Planning District. Current dust regulations are codified here (see Title 15).