08-12-2019 Council Packet - Laserfiche WebLink

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MINUTES OF THE ORONO PLANNING COMMISSION Monday, July 15, 2019 6:30 o'clock p.m. Curtis indicated there are stairs on one side and some of that was affected. The photo on the overhead is from a previous slope failure showing the general area. The stairs were repaired recently and survived this most recent slope failure for the most part. The repair that was done for the previous failure was tiered retaining walls, and the bottom of that repair is what failed. Bollis asked if there was a permit for the previous repair. Curtis stated the property owner went through a conditional use permit process with the City Council but that she does not believe the actual permits were followed through with. As a result, Staff does not know exactly what was done. Ressler asked if there is any clarity as far as relocating any dirt or bringing in dirt from an outside source. Curtis suggested the applicant address that. Dale Gustafson, Applicant, stated this is a complex piece of property and that it is clear that boulders on the steep slope are generally not going to stay there. The slope has failed twice. This system of subterranean grid creates a network under the soil that will hold the slope from top to bottom. On the cross-section at the top, there are timbers going down that help stabilize against the slide and there are also timbers that go across in rows. The difficulty with this type of project is that they cannot work on it at one time. The contractor has to start at the bottom and dig down, put the first crib in, and then each of the subsequent cribs are connected together by the longer timbers that go through it. Right behind the wall there is a section of drainage rock. The moisture that gets in the ground will come down through the clay, encounter the rock, and instead of just collecting there and creating this mass that has freeze/thaw problems, the water will come up to the wall and rock, then go down to the next level and then the next level, and slowly make its way to the bottom level. That will greatly reduce the rate of the runoff, and over time that will help stabilize the slope. Gustafson noted the contractor has been doing this for 30 years and has not experienced a failure yet. When you look at the details on the survey, the surveyor must provide a one -foot contour of the area next to the lake. When you see lines that are parallel to each other, it will tell you that that section was not surveyed. It was marked on the top and the bottom and then the computer determines the difference. When someone tries to build it, those numbers will not match. As they go through this process, the contractor will accommodate the existing grade as they build it. Gustafson stated they are not able to specify exactly where each crib will be. McCutcheon asked if it will be 60 feet long. Curtis indicated it will be in the bottom half or bottom third of the slope. Gustafson stated the boulder walls that remain will be taken out. McCutcheon suggested the applicant provide as much detail as possible to help ensure this will hold, and that if he was the engineer reviewing this, he would look for rise over run, drain tile, and the amount of gravel. Chair Ressler opened the public hearing at 7:42 p.m.