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CASE UPDATE ON 153/155 AVENUE N.W. By: Steve Jankowski, City Engineer Background: You will recall that in June 1994, we received a preliminary engineering report on the alignment for 153/155 Avenue between Variolite and Armstrong Boulevard. The consultants, RLK Associates Ltd., indicated that this alignment could be constructed with only the installation of a retaining wall to prevent encroachment of the roadway into the wetland. Subsequent to an actual wetland delineation, which resulted in the wetland being approximately 25 feet further inland than had been anticipated, ! reported to the Road and Bridge Committee at the February 14 meeting, that the alignment described in the preliminary report could not be constructed without impacting the wetland. I indicated to the Road and Bridge Committee at that time that the consultants and myself would be discussing alternatives with the County and State in an attempt to attain an alignment that would meet our transportation needs without impacting the wetland known as Jeglands Marsh. At this point, our efforts have resulted in two basic alignments. The first option most closely conforms to the original alignment described in the June 1994 preliminary engineering study. This alignment consists of the double S type curves that would convey the traffic from 155th and Variolite directly to a cross intersection at 153rd and Armstrong. In order to retain this alignment, without encroaching on the wetland, a reduction was made in the design speed of the approach curve closest to Armstrong Boulevard from 35 miles per hour down to 30 miles per hour. In addition, the cross-section of this roadway was reduced from 40 feet, in the original design, to a range of between 32 and 38 feet, with parking being restricted along the entire north side of the roadway and along the curves on the south side of the roadway. This alignment also reduces the available property remaining for development between 153/155 and Armstrong Boulevard to between 150 and 200 feet. This represents a reduction of approximately 50 feet in depth from the original preliminary engineering design. A second option for avoiding impact to the wetland consists of extending 155th due west along the section line until intersecting with Armstrong Boulevard. This alignment would require the use of Armstrong Boulevard between Lane and 153rd Avenue to carry east/west traffic wishing to travel on 153/155. A major disadvantage of this option is that it creates conflicts with accelerating and decelerating 153/155 traffic, with faster moving traffic on Armstrong Boulevard. This speed differential can be as high as 35 miles per hour when 153/155 traffic reaches its maximum speed on Armstrong. To mitigate this safety concern, this alternative would include the construction of two additional travel lanes on this segment of Armstrong Boulevard to facilitate the differential traffic speed. This alternative would also require the closure of 154th Lane west of Armstrong to prevent through traffic from moving from 155th down 154th Lane. A variation of this alternative would be the construction of extra lanes on Armstrong Boulevard with the addition of signalized intersections at 155th and 153rd Avenues which would eliminate the safety concern associated with the disparate speeds of 153/155 vehicles using Armstrong Boulevard, as they would be protected during their acceleration and deceleration by stopping traffic on Armstrong. The delay caused by the traffic on Armstrong from this alternative would be a negative aspect of this option. Below is a summary of estimates of total project costs which include project overhead of 25 percent with the original alignment identified in the preliminary engineering report and each of the alternative options discussed above.