09-27-1989 Council Agenda - Laserfiche WebLink

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Sheet No. 7 of the plans show the cross sections and the typical design section. It should be noted that this was a five ton road which was the accepted practice at that time. This consists of two inches of bituminous, nine inches of crushed gravel and 24 inches of sand gravel sub -base. The soil borings taken in 1986 and 1988 bear out the fact that the sub -base extends to a depth of 36 to 48 inches. The original contract called for 7,000 cubic yards while the final estimate paid was 8,700 cubic yards which explains the added thickness. The soil report from Braun recommends four inches of bituminous (for 7 tons capacity which we requested) with eight inches of aggregate over 18 inches of granular material. They also recommend the use of Geotextile Fabric "to reduce the risk of fines being "pumped" into the pavement section. This brings up another question asked at the meeting. Why wasn't this fabric used originally? The answer is that although some type of material existed, it was still in the experimental stage in the late seventies. MnDOT was testing it as it does all new products but had not accepted as late as 1983. It is obvious that this pumping action occurs through traffic action and the pressure of groundwater. The heavier the traffic the more pumping occurs. Reference was made at the meeting that a large part of the damage to the road could be blamed on the development of Allan Avenue and Thunder Bay for which the sand fill and base were hauled over Payne Avenue which is true. At the same time, however, it is also true that a large amount of fill was brought in to raise the lots on Payne Avenue. This fill was an average of three feet over the front third of the lots on both sides of the street. This fill may have gone unnoticed because most of the homeowners didn't.livesthere at the time and secondly it was done on a lot by lot basis. As a rough comparison, we have calculated the amount of material hauled into Allan Avenue and Thunder Bay (base and sub -base) to be about 4,900 cubic yards by comparison. The amount of material hauled into the Payne Avenue lots is about 28,700 cubic yards. Using a conservative figure of 15 yards per load, this translates to 1,913 trucks. To aggravate matters, all this took place during a period of the highest precipitation ever recorded in any five or ten year period. It was recorded from 1977 to 1986. A copy of a release from the State Climatology Office is enclosed. We also enclose a copy of the Plans and Specs for Payne Avenue. We also enclose copies of the Soil Borings by Braun in 1986 and 1988 as well as a report by Twin City Testing in 1987 for Valento Lane which is about 250 feet East of Payne Avenue but contins the same type of soil. Their recommendations are the same as Braun and agree with the construction used on Payne Avenue. Yours truly, ,�� 4, Donald 0. Carley, P.E` Vice President DOC /kt Enclosures Page 65