Now that they've had a chance to complete flow monitoring of Lansing sewers and analyze the data, a representative of GBA architects and engineers told Lansing City Council members Thursday they were able to evaluate the criteria the city had used for sizing pipes.
Tim Scheller of GBA said the evaluation of the existing pipe sizes is preliminary but future activities include confirmation of that evaluation, doing a model of the sewer system for planning purposes and making a final report with recommendations as to sewer rehabilitation priorities and relief sewer improvements.
An important part of their planning had to do with the future growth rates and areas considered priority growth areas. The report focused primarily on the 7-Mile drainage base and the 9-Mile drainage basin, which together amount to 926 acres.
The plan involves a 7-Mile Creek interceptor as well as one for 9-Mile Creek at some point.
One of the major points made during the presentation was a change in the way to determine what size of pipe is needed.
Scheller said the data collected during the flow monitoring suggested the pipes could be smaller than some that followed the city's design criteria.
For example, for the 7-Mile Creek project, what had been conceived as a 36-inch pipe could be downsized to a 32-inch pipe. This could be a little less spent on the pipes, for example, going from about $5.2 million to $4.8 million on that project.
Tony Zell, wastewater superintendent, asked if the council was OK with the new design criteria. Council members wanted the comments of city engineer Matthew Harding, who said he was comfortable with the change.
Scheller said the plans for the first phase should be 90 percent complete within the next couple of weeks, complete enough he could submit them to the state for review.
The next step is putting the project out for bids and Zell said he expected to have bids ready for a council meeting in mid-October. Scheller anticipated construction would start at the first of next year, taking nine months or so.