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Staff describe upsized storm sewers, detention ponds on Burdick and Eleventh And A Half
Summary
A staff member said the project will replace undersized pipes with a 54-inch storm sewer, add detention ponds and use existing railroad-crossing infrastructure to speed runoff and reduce roadway flooding; staff noted the faster conveyance increases required storage and that signal and pavement work have separate completion dates.
A staff member described plans to replace undersized storm sewers and add detention ponds along Burdick and Eleventh And A Half, saying the work will move runoff more quickly into an existing conveyance system and require larger storage.
"We're replacing I think it's a 24 or a 36 with a 54 inches storm sewer," the staff member said, describing how piping will intercept drainage that previously ran over private property and through open channels in the Southwest Knowles subdivision.
The nut of the project, according to staff, is that piping surface flows into a larger, more direct system makes the network more efficient — but that efficiency requires more detention volume because water reaches the pond faster. Staff said the new sewer will extend uphill and that the project currently stops about 300 feet before a planned turn lane so future roadway reconstruction can connect to the pipe.
Staff described choices made to avoid new railroad permitting and costly construction. "We have an existing I think it's a 60 inch pipe that goes underneath the railroad tracks and then goes out right on the south side of the treatment plant. We didn't want to put in another parallel because working with the railroad is tough. It would have added at least a year in permitting," the staff member said. They added that jacking a new large pipe under Burdick and the railroad to reach the river would have cost roughly the same as building the ponds.
Project details noted in the presentation and discussion included: replacing 24- or 36-inch lines with a 54-inch storm sewer; routing intercepted drains from high points and private inlets into the new pipe instead of across private yards (one inlet was described as discharging near a private backyard); connecting two detention ponds with a pipe at the stakes flagged on site; and using existing infrastructure to avoid a new railroad crossing.
Staff said the contractor met a 45-day milestone on Burdick, and that the contractor was slightly ahead of schedule. They said permanent pavement striping cannot be applied until asphalt cures, so temporary markings are used for safety now and permanent markings will be installed after the cure period of about two weeks. Staff also said a traffic signal connected to the project was not expected to be installed until October or November and has a separate completion date.
Questions from a meeting attendee included how much future growth a 54-inch pipe accommodates and whether the new system would meter flows to the river. Staff replied that the drainage basin is largely built out and that the goal is to convey collected runoff through pipe and prevent roadway flooding; they confirmed the facility and land for the ponds are owned by the agency.
Staff emphasized that the project design anticipates future roadway reconstruction on adjacent streets (including a future reconstruction of Sixteenth) and that upsizing the sewer now allows the system to serve a larger drainage area when that reconstruction occurs. The presentation noted that the end of the new storm sewer is north of a local landmark referred to as CBS, and that the drainage area feeding the system is "massive," in staff's words.
The presentation concluded with an invitation from staff for questions and a note that staff would walk people through details they could not answer on site.
