EWEB/New Triad Hospital Relocation Transportation Analysis Report

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PATTERSON STREET UNDERPASS - ESTIMATE OF PROBABLE CONSTRUCTION COSTS except that the 9'6" planting and/or parking strips will be transitioned out before beginning the descent to connect with Patterson Street. Horizontal geometry was developed such that the connection to the EWEB site is aligned with the existing street adjacent to the substation. Vertical geometry was developed using maximum grades of 5% resulting in a minimum clearance under the bridges of 14 ft. In order to accomplish this clearance, it was assumed that the Hwy. 99W grade could be raised approximately 2 ft. over the underpass. Design speed of 20 mph was used for the undercrossing connection to the EWEB site. Illumination The roadway illumination system for Patterson Road Undercrossing Project will be provided by wall mounted GE Versaflood II Wallighter (or equivalent) style fixtures. These fixtures should be ordered with a stippled flat glass Tense to reduce side glare that impedes the motorist's and pedestrian s vision within the undercrossing envelope. Rigid metal conduit, metal junction boxes at each fixture and electrical conductor will be contained within the retaining wall structure to provide power for the illumination system. A power source and lighting controller cabinet will be located outside the undercrossing at a nearby location to accommodate future maintenance of the system. Drainage The estimate is based on assumed flow from the contributing area on 8th Ave. from Sta. 206+00 to Sta. 209+32 (intersection with Patterson Street.); on Patterson Street. from Sta. 2+00 (near Broadway) to Sta 7+77 (intersection with Riverfront Parkway), and on Riverfront Parkway from Sta. 21+23 to Sta. 31+58. Collection, conveyance or treatment of stormwater from areas outside these areas was not included in the estimate. Collection/conveyance pipe contributing runoff to the sag at Sta. 6+60 in Patterson Street, were sized for the 25-year return storm event. Pipe conveying water away from the sag and the pump station was sized for the 100-year return event. The rational method was used to calculate the peak runoff flows. stormwater Pumping Station The pumping station was located north of the intersection of Riverfront Parkway and Patterson Street. Discharge from the pumping station will be via a forcemain tied into a new gravity pipe system in Riverfront Parkway at Sta. 21+23 that will flow northwesterly to the existing 60-inch storm pipe near the intersection with Mill Street. The estimate includes an emergency generator to provide power to the pump station should municipal power be lost. Construction Dewatering Subsurface geologic and hydrogeologic data is not available to make a design level estimate of the dewatering requirements at this location. However a planning level estimate is i : provided here for initial conceptual design. This estimate may vary in magnitude by an additiona130 percent or be reduced by 50 percent. This estimate anticipates that to dewater the construction site the groundwater table will need to be lowered by approximately 10 feet. To accomplish this, we estimate the need for 7 to 10 wells capable of pumping 3500 to PDX/PATTERSON STREET UNDERPASS TECH MEMO 062504 PAGE 2 OF 6