Floodplain Permit Committee Meeting

FLOOD PLAIN PERMIT COMMITTEE MEETING 201 West Gray, Building A, Conference Room D Monday, December 19, 2016 3:30 p.m. Minutes PRESENT: Shawn O’Leary, Director of Public Works Susan Connors, Director of Planning/Community Development Ken Danner, Subdivision Development Manager Jane Hudson, Principal Planner Sherri Stansel, Citizen Member OTHERS PRESENT: Carrie Evenson, Stormwater Engineer Rachel Warila, Staff Greg Hall, Street Superintendent Chris Serrano, Construction Manager Bob Flume, Citizen The meeting was called to order by O’Leary at 3:31. Item No. 1, Approval of Minutes: O’Leary requested a roll call of the committee. Five members of the committee were present and a quorum was established. Scott Sturtz and Neil Suneson were absent. O’Leary called for a motion to approve the minutes from the meeting of November 7, 2016. A motion was made to approve the minutes by Ken Danner. Seconded by Sherri Stansel. Approved 5-0. Item No. 2, Flood Plain Permit Application No. 580: O’Leary stated this application was for the Havenbrook Street bridge replacement project over Brookhaven Creek located approximately 200 ft. east of 36th Avenue N.W. about 1 block south of West Robinson Street. Carrie Evenson gave the Staff Report for this application and Flood Plain Permit Committee meeting December 19, 2016 Page 2 mentioned the applicant was the City of Norman Public Works Department with City Engineer Scott Sturtz who was not present. Evenson stated that the existing bridge consists of 9 -108” corrugated metal pipes (CMPs) that was constructed in 1982. She said that on September 25, 2016, the bridge was closed by the City of Norman due to collapse of the roadway and an investigation by the Department of Public Works determined that the existing corrugated metal stormwater pipes under the roadway were corroded to the extent that 2 of the pipes had collapsed allowing the roadway to settle by over 2 vertical feet. She said with this emergency repair project, the City is proposing to demolish the portions of the existing bridge that must be repaired, and replace the 9 existing 108’ CMPs with 9 new “coated” CMPs of the same size. Evenson presented a map of the bridge project depicting the floodway and floodplain, explaining that the new CMPs will be the same size as the previous pipes but will be coated inside and outside with a protective product to ensure a longer life in corrosive soil conditions. She said work to replace the CMPs will require the construction of a temporary cofferdam to divert stream flow away from half of the CMPs at a time, to provide a dry work environment. She said that other deficient structural elements of the existing bridge will be repaired or replaced as needed and the existing concrete pavement and sidewalk will also be replaced. She said that because the existing CMPs are being replaced with new coated CMPs of the same size in the same location, no rise in the Base Flood Elevation is anticipated. She then presented some photos of the bridge failure which showed why the roadway needed Flood Plain Permit Committee meeting December 19, 2016 Page 3 to be closed and some photos depicting the bridge repairs underway and the removal of the corroded CMPs. Evenson mentioned the Applicable Ordinance Sections were Fill Restrictions in the Floodplain, City Council Approval, No Rise Considerations and Emergency Authority, which have all been addressed in the report. O’Leary introduced Greg Hall, Streets and Stormwater Superintendent, the project manager for this project. He explained that this application was for a significant problem that occurred unexpectedly in September, which led to one minor vehicular accident but that the Norman Police Department worked quickly to close the bridge before there were any injuries. He said that City staff had done a great job exploring options and alternative repairs, including everything from a 2 million dollar bridge to the use of CMPs. O’Leary said the floodplain ordinance dictated part of this choice in the desire not to make any changes in the floodplain. He added that the bridge would be put back exactly the way it was and that part of the work would be done by City crews, saving money in the process. O’Leary asked the FPC if they had any comments of questions regarding this application. Stansel asked if the coated CMPs were a new product and O’Leary responded that they have been around since about the 1970s to 1980s but were not required for use unless placed in reactive soils that tend to react negatively to metal pipe. He explained that reactive soil was not identified during the previous pipe installation and that the bridge did last for 34 years. He said that bridges of this type could last up to 60 years but the reactive soil created holes in the Flood Plain Permit Committee meeting December 19, 2016 Page 4 metal pipe that eventually caused it to collapse. He said that the pipe sizing and the wall configuration was found to be sufficient but the material itself failed, which is why they are replacing it with a coated material that will not react to the soil conditions at the project area. Stansel asked if the soil at Brookhaven Creek is different than the soil in other areas around Norman. O’Leary said there were reactive soils in the western part of the City more often than other parts. Danner said this was one of the reasons the City uses different pipe for the waterlines because they were becoming corroded by the soil. O’Leary stated that metal pipes tend to react worse in the western part of the City than the eastern part due to the soil conditions, so if they choose to use metal pipes coatings are now required. Connors asked if the entire bridge would have to be repaired before the road could be opened up for traffic. O’Leary replied they were repairing half of the bridge and that the road would remain closed because there were 9 pipes in a series and because of equipment access all 9 pipes could not be repaired at the same time. He said all repairs would need to be made before the road could reopen, which could happen around February or March, 2017; if the weather cooperates and everything else goes as expected. Stansel asked where the concrete from the repair would be hauled off to and Greg Hall said that there was very little but that it would be broken into pieces and used as rip rap material. O’Leary asked Bob Flume if he had any questions or comments. Flume said he was a property owner on 36th Street and he had received a floodplain notice in the mail and he had come to the meeting early and already discussed his concerns with Carrie Evenson. O’Leary asked for Flood Plain Permit Committee meeting December 19, 2016 Page 5 a motion from the committee. Danner recommended approval of Floodplain Permit Committee application #580, which was seconded by Connors. Motion approved 5-0. A motion was made by Danner which was seconded by Connors. Approved 5-0. Item No. 3, Miscellaneous Discussion: 1. There were no applications for the January 3, 2017 meeting. 2. There were no pending application for the January 17, 2017 meeting. O’Leary asked if there was anything else from the committee and there was not. O’Leary called for a motion to adjourn. Connors motioned to adjourn, seconded by Danner. Motion was approved 5-0. Meeting adjourned at 3:45 p.m.