Agenda Packets - 2008/03/10 - Laserfiche WebLink

Home Browse Search

Mounds View, Minnesota Project No: 435-08131-0 2008 Street Maintenance Project Page 3 Required Improvements The surface of all streets proposed for the 2008 Street Maintenance Project are in good condition. The required maintenance activities needed on these streets consist mainly of sealing transverse surface cracks that have developed in the bituminous, and application of a protective coating to the street surface. A discussion of the maintenance activities follows: CRACK SEAL Bituminous surfaces are susceptible to expansion and contraction in extreme temperatures. Due to this thermal movement, transverse cracks will typically develop in the surface of a bituminous street within a year or two after construction. These cracks frequently occur at regular intervals along the length of a street, and at locations of structures such as manholes and gate valve boxes. The purpose of crack sealing is to prevent widening of the cracks, and to prevent water from seeping through the cracks into the street base and subgrade, which could significantly accelerate deterioration of the street surface. Crack sealing is performed by sawing the surface of the crack to a width of ¾ to 1 inch by a depth of ¾ inch. This is done to create smooth edges within the crack to promote adhesion of the filler material. The sawed area is thoroughly cleaned using high pressure air blasting. Filler material is then placed in the crack. The filler is typically a hot-pour elastic type sealer that is placed using specialized equipment. The material remains pliable to extreme cold temperatures, allowing expansion and contraction of the crack while remaining bonded to the sides of the saw cut area. The procedure described above is commonly referred to as “route and seal”, and is effective only on narrow cracks, less than about ½ inch in width. City Staff has indicated that all required crack sealing will be performed by City forces, which will result in a project cost savings to the City. The only exception to this would be Hillview Road and the parking lot at Lakeside Lions Park. Since those facilities are jointly owned with Spring Lake Park, it is proposed that any necessary crack sealing on them would be performed as part of the construction contract. This would allow for ready identification of the complete maintenance cost expended on those facilities, and ensure equitable participation by each City towards those costs. SEAL COAT Bituminous seal coat is the application of specific rates of bituminous material (oil) and aggregate material (rock chips) on an existing bituminous roadway surface. After a curing period, the loose aggregate material is swept from the street, leaving behind only what has satisfactorily bonded to the surface. There are a variety of aggregate materials available for a seal coat operation. This Report recommends that the aggregate used for this project be a crushed trap rock, with maximum chip size of ¼-inch. This material is designated as type FA-2, and has been used successfully on several seal coat projects in the area for streets with similar characteristics to those in the proposed 2008 Street Maintenance Project. FA-2 is also the type of aggregate that was used on the 2007 Street Maintenance Project in Mounds View. Seal coating is a process that can extend the life of paved roadways by slowing the oxidation process of the bituminous surface. Another benefit of a seal coat operation is waterproofing of the street surface. This prevents water from entering the street base, which can accelerate the deterioration of the street surface