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■ E�sting noise mitigation may cause a situation where additional mitigation does not provide additional noise-level reduction. ■ Cross-streets may create a situation where noise mitigation cannot be constructed continuously along the noise source. ■ Residential density is low. Cost reasonableness calculations are included in Table 6 for each modeled noise wall. Only one of the noise walls placed within the model to ma�mize decibel reduction at impacted receptors meet the Mn/DOT minimum criteria of $3,250 per decibel of reduction per residence. Wall #1 achieved a cost of $3,054 per decibel of reduction per residence. Wall #2 and Wall #3 do not meet the cost reasonableness requirement for wall consideration. The noise reductions per receptor less than SdB are not included within the overall per Mn/DOT policyi. "Feasibility" is defined as whether a noise wall may be built considering proper setback, sight lines, and location. Based upon the location of the modeled Wall #1, taking into account the proper setback, sight lines, and location, Wall #1 is a feasible noise mitigation alternative. 4.3 Evaluation of Other Noise Abatement Measures Noise walls have been chosen as the most cost-effective noise mitigation measure available for this project. Other noise mitigation measures have been considered, as listed in 23 CFR 772.13(c). They are addressed below: a. Traffic management measures: The primary purpose of the facility is to move people and goods. Restrictions of certain vehicles or speeds would be inconsistent with the purpose of the project. b. Alteration of horizontal and vertical alignments: The project was realigned for practical reasons based on grade and safety. Acquisition of real property or interests therein (predominantly unimproved property) to serve as a buffer zone to preempt development that would be adversely impacted by traffic noise: Acquisition of property for noise mitigation purposes is not a part of the proj ect scope. However, efforts will be made through local planning authorities to regulate land development in such a way that noise-sensitive land uses are either prohibited from being located adjacent to a highway, or that the developments are planned, designed, and constructed in such a way that noise impacts are minimized. d. Noise insulation of public use or nonprofit institutional structures: This is a noise abatement measure that would not affect the noise level violations of Minnesota State Noise Standards because these standards are exterior standards. FHWA guidelines and Mn/DOT policy recommend that only public buildings, such as schools and hospitals, be considered for acoustical insulation. 5.0 Noise Analysis Conclusions and Summary Traffic noise impacts occur for TH36 when modeled traffic noise levels approach or exceed the FHWA NAC-1 (70dB) level by one decibel, when impacts are modeled exceeding state noise guidelines, or those which noise levels exceed the FHWA NAC category B criteria of a SdB or more increase per receptor. As stipulated in Minnesota Statute 116.07, Subd. 2a, Rice Street and County Road B are exempt from the state noise standards, therefore noise impacts occur when modeled traffic noise levels approach or exceed the FHWA NAC-1 (70dB) level by one decibel or those which noise levels exceed the FHWA NAC category B criteria of a SdB or more increase per receptor. Noise Analysis RAMSP 105803 TH 36 and Rice Street Interchange Page 7