Highway Projects

MDOT I-495 / I-270 Noise and Air Quality Analysis

HMMH was part of a large team that worked to update a shelved Environmental Impact Statement in Maryland to address widening alternatives to the I-270 and I-495 highways in the Washington, D.C. metro area.

HMMH updated the noise prediction models to reflect current Federal Highway Administration and state regulations, as well as to accommodate the revised alternatives and current land use. In addition, HMMH evaluated noise abatement feasibility and reasonableness for all sections along I-270 and provided significant contributions to the documentation, graphics, and quality control review.

HMMH’s air quality analysis participation included a technical review of the DEIS and Air Quality Technical Report. The air quality analysis consisted of evaluating seven Alternatives consistent with EPA, FHWA, and Maryland DOT (MDOT) methodologies and guidelines for conducting an air quality Project Level analysis.

A carbon monoxide (CO) hot spot analysis was conducted for the affected intersections and roadway segments using the EPA MOVES and CAL3QHC dispersion model. A quantitative MSAT analysis was conducted to address mobile source air toxics (MSATs) using the EPA MOVES model along with Project traffic assessments consistent with FHWA guidance and methodologies. A qualitative greenhouse gas (GHG) analysis was also conducted similar to the MSAT analysis using MOVES to evaluate potential GHG impacts from each Alternative. HMMH was responsible for addressing comments from EPA, MDOT, and FHWA for the DEIS and Air Quality Technical Report.