07-29-09 Drainage and Flooding Committee minutes

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Mr. Ron Bottoms August 14, 2009 Page 2 of 3 equalize the flow in each pipe. Alternative 3 was the least expensive alternative with a construction estimate of approximately $1.37M. Previous Study Alternative 4 Alternative 4 included lowering Fleetwood Drive approximately 1.7 feet from Mesquite Drive north to Linwood, transitions to the side street and constructing a new 5 year storm sewer system under Fleetwood. Portions of the existing storm sewer system would be in conflict with the proposed lowered Fleetwood so a new 5 year storm sewer system was proposed. The construction cost was estimated at $2.2M for Alternative 4. Residents of Fairmont Park East Subdivision have made 'comments in support of Alternative 4 over Alternative 3 during some of the Drainage Conilnittee meetings. New detail survey data along Fleetwood ,. The City of La Porte used staff resources to develop a detailed survey alol1gfleetwood. The survey obtained more detail elevations andupdated.'information along Fleetwood from Mesquite north to almost Spencer Highway. Tq~ ~urvey obtained detail elevations along the roadway as well as elevati~rs of the storm sewer inlets along the side streets. This new survey data allowed us to reev;allJate Fleetwoodinmore detail rather than using only older reference drawings. As a resulfof the new survey a new Alternative 5 was developed. Alternative 5 Alternative 5 include~ iowenngpart of Fleetwood Road from Mulberry Drive north to South Spruce and constglcting qnew 5year storm sewer system. This alternative is shown on the attached exhibitS and thetonstruction cost is estimated at $1.66M. The benefit of this Alterna~veis to provide 'for better'sheet flow out of the subdivision during storm events higher "than'jh;~ 5 ye?TTI' event but only includes the complete rebuilding of FleetwQpd for abour.J,400 feet" Alternative 5 includes about 1,000 feet less of impfbv'ements to Fleetwood compared to Alternative 4. This Alternative 5 is more expensivetlian Alternative'} but also provides for more flow capacity during large storm events by low~ri,rg the res1:fiction of flow along Fleetwood and allowing the large storm event flows to couti,pue to flow south towards the ditch. Overflow swale or storm sewer outfall pipe As part of all of the alternatives evaluated an overflow swale or storm sewer outfall pipe is proposed to be constructed from Fleetwood Drive to the receiving ditch to compliment the capacity of the proposed Alternative. The overflow swale or storm sewer outfall pipe are critical elements to improve the drainage for Fairmont Park East and need to be constructed as a minimum even if changes or improvements to Fleetwood are delayed.