"Hot Spots" Stationary Diesel Engine Screening Risk Assessment Tables
CARB and local air districts are coordinating the stationary diesel compression ignition engine air toxic control measure (ATCM) and the Air Toxics "Hot Spots" Program (AB 2588) to make it easier for facilities to comply with both programs.
In order to streamline the evaluation of diesel engines potentially subject to the AB 2588 "Hot Spots" Program, screening risk assessment tables have been developed that engine owners can use to estimate their overall facility risk from diesel engine exhaust particulate matter (PM) from stationary diesel engines. Because cancer effects from diesel PM generally drive the risk from diesel engines, chronic and acute affects are not included in these tables. The risk tables (based on diesel PM) are listed below.
Draft Screening Risk Assessment Tables for Stationary Diesel Engines
|50% Load (Urban)||50hp||100hp||175hp||300hp||600hp||750hp||1500hp|
|75% Load (Urban)||50hp||100hp||200hp||550hp||1500hp||2600hp|
|75% Load (Rural)||200hp||550hp||1500hp|
These tables are health-conservative and should only be used for screening purposes. The local air district will determine if a more thorough evaluation is necessary. The risk tables for 50% and 75% load were developed using results from an air dispersion model (ISCST3) that estimates how emissions from a diesel engine are distributed to the surrounding area. These tables are based on the same information provided in Appendix E of the stationary diesel engine ATCM staff report published in 2003. Average release parameters such as stack height, temperature, and velocity, were taken from test data for each engine size and used in the dispersion modeling. For these tables, West Los Angeles, 1981, meteorological data were selected as the input to the ISCST3 model. All of the screening tables assume that all receptors are directly downwind from all diesel engines.
What information is required?
In order to use the risk tables, the following data fields are required:
Percent of maximum rated brake horsepower (50% or 75%)
Measured in meters from each diesel engine to its nearest receptor - residential or commercial.
Measured in units of grams per horsepower-hour; assume 1.0 g/bhp-hr if unknown.
Horsepower (HP); use the spreadsheet that is closest to the size of your engine.
Number of annual operating hours for each engine for non-emergency use.
Air dispersion modeling parameter determined by the district.
What do the results mean?
The total risk from multiple stationary diesel engines at a facility can be estimated using the tables provided. Generally, if the calculated overall facility risk is less than 10 per million, the facility will not have to do any further risk analysis, since the public notification and risk reduction thresholds are not exceeded. Facilities with an estimated risk above 10 per million may work with their local air district to complete a more refined health risk analysis using site-specific information including local meteorology data. Since the tables were developed using a health-conservative estimate of risk, facilities may find that their risk is substantially less when a more refined analysis is completed.
How do I calculate emissions and risk from an engine with control equipment?
In the absence of source test data, and at the discretion of the local air district, facilities may estimate their controlled emissions using the following assumptions:
|Control Equipment||% reduction in emissions and risk from baseline uncontrolled emission levels|
|Diesel particulate filter (DPF)||up to 85%|
|Diesel oxygen catalyst (DOC)||up to 30%|