Several drainage improvement studies were performed in 2018 in response to flood events experienced in the City from 2015 through 2017 with Hurricane Harvey. Two of the study areas included the Riverbend subdivision area, which was impacted by tailwater conditions on Oyster Creek, and the Lakebend Drive/Central Drive area of Sugar Creek, which was impacted due to excessive street ponding and high water surface elevations in lakes adjacent to the neighborhood. The street ponding depth and duration has impacted emergency response times in in both areas during heavy rain events in recent years. The Riverbend neighborhood is served by multiple drainage systems, including a storm water conveyance system (with pipes and street curb inlets) that outfalls into Oyster Creek downstream of Dam #3. This portion of Oyster Creek has a flow control structure (weir) in it that maintains water levels within Oyster Creek Park.   The Lakebend area, which is a separate drainage system from the Riverbend neighborhood, is served by one drainage system which flows through Sugar Creek Country Club and eventually outfalls into Oyster Creek.

At the completion of the studies, improvements were recommended for both locations to improve the runoff rates and reduce the ponding elevations within the streets in each area. The improvements to the Riverbend area include modification of the existing metal sheet pile weir structure with a rectangular notched weir. The structure is embedded in Oyster Creek on the west side of the existing bridge at Dulles Avenue between Randall Oak Drive and Plantation Colony Drive. The modification includes cutting and removing the top section of the metal sheet pile on each side of the weir opening to match the weir opening elevation. This will allow for increased flows over the weir during an extreme event and reduce tailwater conditions that could contribute to flooding upstream of the weir. Furthermore, these modifications will reduce the ponding depth and duration in the Riverbend neighborhood, and other adjacent neighborhoods, during major storm events and will improve the hydraulic efficiency through the existing outfall.   

The improvements to the Lakebend Drive/Central Drive area will include modifications to the structure located at the detention pond on Central Drive, adjacent to the United Healthcare Building, southeast of US59 and the  feeder road. The improvements consist of the removal, modification and replacement of the two (2) existing metal trash screens affixed to a 54-in storm sewer outfall. The proposed new screens will allow for improved flow in case of an extreme event and avoid extended flooding in the surrounding area. Furthermore, these modifications will reduce the ponding depth and duration in the Lakebend Drive/Central Drive area during major storm events and will improve the hydraulic efficiency through the existing outfall.

The design contract for the project was approved by City Council in February 2019 and design was completed in October 2019. An Invitation to Bid was advertised on November 6 through 21, 2019. Two (2) bids were received on November 21, 2019. A bid summary of the two bids is shown below:   

The engineer's estimate for this project is about $100,000. NBG Constructors, Inc. (NBG) was the apparent low bidder with a total construction contract amount of $130,000.

The available funding in CIP DR1901 is $102,000. Additional funding will be needed to cover the construction contract and contingency of $7,000 for a total budget amount of $137,000.  Therefore, a budget amendment of $35,000 from General Fund Contingency is being requested to fund the recommended construction project with contingency.

Lockwood, Andrew, & Newnam, Inc. (LAN) completed a review and evaluation of the bids, and provided a letter of recommendation indicating NBG is capable of completing a project of this nature. In addition, NBG has previously completed work for the City on different projects with positive results. Upon City Council approval, the Notice to Proceed will be issued in January with a contract time of 60 calendar days.

In accordance with Policy CO-110, Notification of Construction Impacts and Service Interruptions, the project is classified as a Neighborhood Project. No interruptions of any services is anticipated during the construction on this project.  Project information will be provided on the City’s website about both projects – neither of which will result in any interruptions to any existing utilities or require the City to enter any private property or easements.

The Engineering and Public Works Departments recommend that the City Council authorize the execution of a construction contract with NBG Constructors, Inc. for the modifications of the outfall structure at the existing detention pond at Central Drive (UnitedHealth Building) and the modifications of the existing weir at Oyster Creek and Dulles Avenue, CIP DR1901, in the amount of $130,000; and a budget amendment, in the amount of $35,000, from the General Fund Contingency to CIP DR1901.