2013-050 - Addendum to the Final Environment Imapct Report No. 2006-01

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CONSTRUCTION ACTIVITY IMPACTS Dust is typically the primary concern during construction of new homes and infrastructure. Because such emissions are not amenable to collection and discharge through a controlled source, they are called "fugitive emissions." Emission rates vary as a function of many parameters (soil silt, soil moisture, wind speed, area disturbed, number of vehicles, depth of disturbance or excavation, etc.). These parameters are not known with any reasonable certainty prior to project development and may change from day to day. Any assignment of specific parameters to an unknown future date is speculative and conjectural. Because of the inherent uncertainty in the predictive factors for estimating fugitive dust generation, regulatory agencies typically use one universal "default" factor based on the area disturbed assuming that all other input parameters into emission rate prediction fall into midrange average values. This assumption may or may not be totally applicable to site - specific conditions on the proposed project site. As noted previously, emissions estimation for project - specific fugitive dust sources is therefore characterized by a considerable degree of imprecision. Average daily PM -10 emissions during site grading and other disturbance average about 10 pounds per acre. This estimate presumes the use of reasonably available control measures (RACMs). The SCAQMD requires the use of best available control measures (BACMs) for fugitive dust from construction activities. With the use of BACMs, fugitive dust emissions can be reduced to 1-2 pounds per day per acre disturbed. Current research in particulate - exposure health suggests that the most adverse effects derive from ultra -small diameter particulate matter comprised of chemically reactive pollutants such as sulfates, nitrates or organic material. A national clean air standard for particulate matter of 2.5 microns or smaller in diameter (called "PM -2.5 ") was adopted in 1997. A limited amount of construction activity particulate matter is in the PM -2.5 range. PM -2.5 emissions are estimated to comprise 10 -20 percent of PM- 10. In addition to fine particles that remain suspended in the atmosphere semi - indefinitely, construction activities generate many larger particles with shorter atmospheric residence times. This dust is comprised mainly of large diameter inert silicates that are chemically non - reactive and are further readily filtered out by human breathing passages. These fugitive dust particles are therefore more of a potential soiling nuisance as they settle out on parked cars, outdoor furniture or landscape foliage rather than any adverse health hazard. Exhaust emissions will result from on and off -site heavy equipment. The types and numbers of equipment will vary among contractors such that such emissions cannot be quantified with certainty. Demolition and grading activities will shift towards construction and paving, etc. The CalEEMod was developed by the SCAQMD and provides a model to calculate both construction emissions and operational emissions from a residential land use project. It calculates both the daily maximum and annual average emissions for criteria pollutants as well as total or annual greenhouse gas (GHG) emissions. The CalEEMod 2011. 1.1 computer model was YAI"P SI, aQ '4