Agenda - Council - 10/26/2021 - Laserfiche WebLink

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We were not provided any information regarding traffic volumes such as Average Annual Daily Traffic (AADT) counts or vehicle distribution for the roadways. We assumed these roadways will be utilized mainly by automobiles, light trucks and school buses with some heavier vehicles such as garbage trucks and UPS or FedEx type delivery vehicles. For the purposes of this evaluation, we assume the street will generally be classified or described as a "typical urban street" and estimate the pavement will be designed for a maximum of 100,000 Equivalent Single Axle Loads (EASL's) over a design life of 20 years. The ESAL's have not been adjusted for any future growth. Changes in the nature, design, or location of all or parts of this project may occur. Likewise, if the proposed traffic volumes exceed these values we should be informed. Additional analyses and revised recommendations may be necessary. 4.2 Discussion Roadways/pavements Based on a brief review of historical aerial photographs available on Google Earth and the Anoka County GIS website it appears that the streets were originally built around 1997 and appear to be approaching or have exceeded their assumed 20-year design life. It appears some, or all, of the streets were subject to some periodic maintenance that included seal coating/chip coating. Evidence of fairly recent seal coating/chip coating was visible on cores 3, 4, 5 and 7 obtained from Iodine Court, Junkite Street and 146th Circle. Evidence of recent seal coating/chip coating was not readily apparent at the remaining locations. We observed longitudinal and transvers cracks with some "alligator" or fatigue cracking of the pavement surfaces. The cracking observed could be the result of a combination of factors including; inadequate pavement thickness, pavement age and/or possibly frost action/frost heave. Longitudinal cracking are cracks parallel to the pavement centerline or laydown direction. These can be caused by poor joint construction, reflective cracking from an underlying layer, fatigue cracking or top -down cracking resulting from the age of the pavement or due to expansion and contraction of the pavement surface or increased traffic loads on the pavements. Transverse cracking are cracks perpendicular to the roadway centerline or laydown direction. These are often caused by shrinkage of the pavement surface, reflective cracking from an underlying layer or top -down cracking. Alligator or fatigue cracking can be symptomatic of poor subgrade soils and/or inadequate pavement thickness. Aggregate Base An apparent aggregate base layer was observed below the pavements at each boring location. The aggregate base appeared to contain little gravel and because of that it was identified as Possible Aggregate Base on the boring logs. Based on our observations the aggregate base or Possible Aggregate Base may not meet MN/DOT gradation specifications for Class 5 aggregate base. It is possible that the Possible Aggregate base was initially placed as new or virgin Class 5 aggregate base but has degraded over time due to traffic and possibly frost action. Soils The borings encountered sandy subgrade soils including; poorly graded sand and poorly graded sand with silt which correspond to the ASTM Classifications SP and SP-SM, respectively. 7