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4.5 AIR QUALITY Construction activities would also affect regional air quality. The daily emissions shown in Table 4.5-3 would increase the emission burden within San Joaquin County and larger San Joaquin Valley Air Basin. Comparison of these emission totals to the "thresholds of significance" recommended by the San Joaquin Valley Air Pollution Control District-San Joaquin Unit shows that only emissions of PM-10 from the project would exceed the threshold. Since San Joaquin County is non-attainment for PM-10,this impact is considered significant. Miti ag tion 4.5-1(a) The project as currently proposed incorporates several particulate strategies. Overall dust control is proposed to be accomplished using water sprinklers and a watering truck to keep exposed surfaces damp. The haul road is proposed to be graveled with six inches of road base aggregate that would be treated with penetrating oil for dust control. Watering can be expected to provide about 50 percent dust control, while the use of a graveled and oiled haul road would reduce emissions from the haul road by about 80 percent (compared to a dirt road). These measures have been assumed to be in use in the analysis of impacts, and would not be sufficient by themselves to reduce PM-10 emissions to a less-than-significant level. 4.5-1(b) The severity of construction impacts can be reduced to a less-than-significant level through the application of additional mitigation measures. To ensure Aw eonstr-u A grading permit should not be issued unless a satisfactory PM-10 Dust Prevention and Control Plan has been approved by the San Joaquin Valley Unified Air Pollution Control Board. This plan should specify the methods of control that will be utilized, demonstrate the availability of needed equipment andpersonnel,and identify a responsible individual who, if needed, can authorize the implementation of additional measures. The Plan should, at a minimum, include the following: • suspension of dust-producing activities during periods of high winds when dust control measures are unable to avoid visible dust plumes; • during the dry season (May-October),provide equipment and staffing for watering of all exposed or disturbed soil surfaces at least twice daily, including weekends and holidays. An appropriate dust palliative or suppressant, added to water before application, should be utilized; • continuously sprinkle or chemically stabilize temporary stockpiles of soil. Soils to be stockpiled for longer than three months should be seeded and watered; • require that all trucks leaving the site drive over a grid of parallel metal bars or metal grating designed to remove mud from the tires; 4.5-8