Overview

Assistance to Air Pollution Control Agencies

Regulatory and Strategic Analysis

Public Health Analysis

Energy Facility Licensing

Permitting Support

Compliance Support

Litigation Support

Vehicle & Engine Certification Assistance

Greenhouse Gas Assistance

  - Mobile Source Emissions

  - Stationary Source Emissions

Emission Testing Facilities

I/M Support Services

Modeling Capabilities & Data Analysis

Questions regarding Modeling Capabilities & Data Analysis?

Sierra maintains a wide variety of emission factor and air quality models and has extensive experience and expertise in applying these models in regulatory compliance and air quality planning applications.

Mobile Source Emission Factor Models – Emission factor models include the U.S. Environmental Protection Agency’s MOBILE and NONROAD series and the California Air Resources Board’s EMFAC and OFFROAD series of models.  In addition, Sierra has adapted and implemented a vehicle simulation model called “VEHSIM” for a variety of applications where there is a need to simulate the effects of changes in vehicle and engine design or changes in vehicle driving patterns on emissions and fuel efficiency.  In each of these cases, Sierra has experience not only in running these models, but also in customizing them for client-specific applications.

Air Dispersion Models – Sierra provides air quality modeling services using a range of EPA and state guideline models.  Screening and refined modeling is performed in support of air quality permitting, environmental documentation (NEPA and CEQA compliance), and regional and local planning using models such as AERMOD, CALINE3, CALPUFF, CTSCREEN, ISCST3, OCD, RTDM and SCREEN3, CAL3QHCR, and VISCREEN.  Models such as AERMOD, CALPUFF, and ISCST3 require extensive meteorological data sets, which Sierra is experienced in assembling using software such as AERMET, CALMET, PCRAMMET, and MPRM.  Sierra also has expertise in the specialized air dispersion models used in hazardous materials offsite consequence modeling, including RMP*COMP, SLAB and DEGADIS.  Sierra has in-depth experience in health risk assessment (HRA) modeling using California’s Hot Spots and Assessment Program (HARP) model.  ISCST3 is imbedded in this model, and Sierra has developed a methodology to allow an external dispersion model such as AERMOD or ISCST3 to directly estimate cancer risk and non-cancer chronic and acute health hazard.

Data Library – Sierra maintains an extensive library of data resources containing air quality, emissions inventory, and motor vehicle test data for California and a number of other states.  Motor vehicle data include emission control system descriptions (dating from 1973), vehicle emissions test results from surveillance testing and I/M undercover testing conducted by the California Air Resources Board and the U.S. Environmental Protection Agency, and millions of test records from a variety of state I/M programs.

Data Analysis – Sierra has extensive experience in analyzing large volumes of air quality, travel characteristics, and vehicle emissions data.  This experience has been applied in a variety of applications, including air quality planning, emission inventory development and forecasting, air quality trend analysis and attainment demonstration, mobile source emission factor model development, transportation planning, and vehicle driving pattern/drive cycle analyses.