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John Stark, Community Development Director City ofRoseville November 17, 2006 Page 23 The MPCA defines daytime as 7 a.m. to 10 p.m. and nighttime as 10 p.m. to 7 a.m. Traffic noise analyses are typically conducted for the peak noise hour during both daytime and nighttime when free flow traffic conditions create the highest noise levels. The existing (year 2006) and future year 2030 build conditions p.m. peak hour traffic volumes were used to model daytime traffic noise levels. The nighttime peak hour traffic is generally from 6:00 a.m. to 7:00 a.m., just prior to the morning rush hour. Nighttime traffic volumes were estimated for project area roadways fi'01ll average daily traffic (ADT)2 volumes, generally between two and four percent of the ADT. However, peak noise levels do not always correspond to peak traffic hours. This is the case when increased congestion causes reduced speeds. Level of service C conditions is considered to represent peak traffic noise conditions. To account for this phenomenon, a default traffic volume of 1,500 vehicles per lane per hour for 1-35W and 600 vehicles per lane per hour for local roadways was used in the noise models when existing and projected traffic volumes exceeded these thresholds. Existing (year 2006) and future (year 2030) daytime and nighttime traffie noise levels are shown in Tables 8 and 9, respectively. Noise levels currently exceed State daytime and nigbttime noise standards at all three modeled receptor loeations (existing year 2006). Traffic noise levels will increase from one to three dBA from existing (year 2006) to year 2030 Scenario lA build conditions; whereas, some areas are anticipated to experience no change in traffic noise levels from existing (year 2006) to year 2030 Scenario 1B build conditions. The observed increases are the result of higher traffic volumes under year 2030 build conditions. Future traffic noise levels are anticipated to be similar between the two redevelopment scenarios. Traffic noise levels are anticipated to be the same or one dBA greater under redevelopment Scenario IA. The largest increase in traffic noise was observed at Receptor 3 under year 2030 Scenario lA build conditions. Receptor 3 was estimated to have a three dBA (nighttime LlO) and four dBA (nighttime Lsa) increase from existing to build conditions under redevelopment Scenario lA. A three dBA change is barely perceptible to the human ear; a five dBA change is noticeable.3 Please recall that the nighttime peak hour traffic is generally from 6:00 a.m. to 7:00 a.m., just prior to the morning rush hour. Year 2030 build conditions analyses assume a similar heavy truck percentage as the existing models. However, under the two future redevelopment scenarios, land uses in the Twin Lakes AUAR area include more residential and office/business uses. These types of land uses typically generate less heavy truck traffic, and as a result, the heavy truck percentage on the adjacent roadways will likely be lower than what was modeled. Therefore, it is likely that future traffic noise levels will be unchanged from existing conditions and thus the analysis results present the worst-case potential noise scenario. 2 Average daily traffic (ADT) volumes for project area roadways in the noise models was estimated using p.m. peak hour volumes. The p.m. peak hour volumes \\'ere assumed to be approximately 8 to 12 percent of ADT, based on percentages used for the 2001 AUAR traffic noise analysis. 3 Minnesota Pollution Control. 1999. A Guide to Noise Control in Afinnesota.