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noise analysis, and comparison to the Minnesota State Noise Standards and the Federal Noise Abatement Criteria. Receptor locations are shown on Figure 1 in Appendix B. All receptors were entered into the MINNOISE model using Alpha factors equaling 0.5. Alpha factors within MINNOISE models are factors that control the rate at which noise is propagated, or at what rate over distance, the noise is diminished. An Alpha factor of 0.5 within MINNOISE has a noise rate of decay of 4.SdB per doubling of distance. This is an appropriate value for propagation over soft ground with an at-grade roadway and first floor receptor. MINNOISE calculates the amount of potential noise directly related to traffic speeds, traffic mix (% cars, trucks, heavy trucks), and peak hour percentages of predicted future traffic (Design Year 2033 "Build" and Design Year 2033 "No Build"). Traffic volumes were taken from the traffic analysis completed for the EA and were available for the "Daytime" and "Nighttime" peak volume times of: ■ the hour from 4:30PM to 5:30PM (Daytime) and ■ the hour from 6AM to 7AM (Nighttime). Traffic counts were available along TH36, the on and off ramps for TH36, County Rd. B, and Rice Street for the peak times of morning rush hour 7AM to 8AM and evening rush hour 4:30PM to 5:30PM. The peak "nighttime" traffic hour (between lOPM and 7AM) was the hour between 6AM and 7AM. Traffic count information was only available along TH36 during the "nighttime" hours. No traffic count information was available for the on and off ramps to and from TH36 or along Rice St. and County Rd. B for the peak "nighttime" hour of 6AM to 7AM. The percent change was calculated for the traffic counts along TH36 between the 6AM to 7AM hour and the 7AM to 8AM hour. The percent change (66%) from the available Hwy 36 data was then applied to traffic along Rice St., Cty. B, and the entrance and e�t ramps to and from TH36. These calculated traffic counts are presented as the "nighttime" counts in Table 5. Speed assumptions were based on posted speeds that range from 35mph to SSmph. When noise impacts are identified, a noise wall mitigation analysis must be performed. 4.0 Noise Wall Mitigation Analysis With noise levels exceeding state and federal noise standards, a mitigation analysis was required and completed to determine if ineasures, such as a noise wall, are reasonable and effective in attenuating the noise at those locations. To have a noise wall considered for mitigation, one of the following factors must e�st ■ The noise standards are presently in excess of state noise standards. ■ The predicted noise levels are expected to be in excess of the state noise standards for the design year of the project. ■ The noise levels are predicted to be "substantially" above current noise levels in the project design year. "Substantial" is defined as a SdB or greater increase in noise. ■ The predicted noise level for the design year approaches or exceeds the acceptable limit. "Approaching" is defined as noise levels being within 1dB of the FHWA NAC. In this instance, levels predicted as 69dB are considered approaching the FHWA NAC of 70dB. If one or more of the above conditions are met, noise walls need to be considered based upon cost reasonableness and noise wall feasibility. Noise Analysis RAMSP 105803 TH 36 and Rice Street Interchange Page 5