Title
Consider/Discuss/Act on a Resolution of the City of McKinney, Texas, Authorizing Variances to the No Floodplain Rise Restriction of the Stormwater Ordinance for Certain Properties Along Honey Creek and the East Fork of the Trinity River Near U.S. 75
Summary
COUNCIL GOAL: Enhance the Quality of Life in McKinney
Direction for Strategic and Economic Growth
MEETING DATE: March 21, 2017
DEPARTMENT: Development Services / Engineering
CONTACT: Mark Hines, PE, Director of Engineering
RECOMMENDED CITY COUNCIL ACTION:
• Approval of Resolution.
ITEM SUMMARY:
• Developers along Honey Creek and the East Fork of the Trinity River (EFTR) are proposing projects that will increase the fully-developed, 100-year floodplain along both creeks by no more than 0.06 feet (approximately 3/4") on properties upstream and downstream of U.S. 75. The location of the property is shown on the attached map.
• The Stormwater Ordinance prohibits increasing the fully-developed, 100-year floodplain on properties owned by others without the affected property owner’s written consent and drainage or floodplain easements.
• Staff recommends approval of a variance to authorize the proposed increase in the floodplain up to a maximum of 0.06 feet.
• In order to alleviate any adverse impacts of the Water Surface Elevation (WSE) increase on the future development of affected adjacent properties, staff also recommends a variance to the Storm Water Management Ordinance to allow a decrease in the freeboard requirement on those affected properties by the same amount of the floodplain increase on said properties. Thus, instead of requiring 2.00 feet of freeboard, as little as 1.94 feet would be required. The affected properties are shown on the attached map along with the proposed change in floodplain elevation and corresponding reduction in the freeboard requirement.
• Affected property owners will receive notification of floodplain changes and variances granted.
BACKGROUND INFORMATION:
• After completion of the TxDOT U.S. 75 project and the City of McKinney F.M. 543 project, the developer’s properties experienced an increase in the fully-developed, 100-year EFTR floodplain of 0.69 feet (approximately 8-1/4”).
• The TxDOT U.S. 75 project, if completed as a stand-alone project, would have created significant WSE increases downstream of U.S. 75 (as much as 1.13 feet) and decreases upstream of U.S. 75 for both creeks.
• The McKinney F.M. 543 project was undertaken in the same timeframe as the TxDOT U.S. 75 project. Based on an analysis completed by Freese and Nichols on behalf of the City, this project in combination with the U.S. 75 project reduced some of the more extreme WSE changes downstream of U.S. 75, but resulted in WSE increases upstream of U.S. 75 along the EFTR. The combination of the projects better balanced the floodplain elevation changes on properties adjacent to U.S. 75 to the point where no property was singly affected significantly more than the others. This is considered good and sufficient cause to request the granting of the variance regarding an increase in WSE.
• The developer's engineer has attempted various site configurations in an effort to eliminate any off-site WSE increases. However, this is not possible without an unacceptable loss of approximately 50 acres of developable property. This is above and beyond the amount already lost to meet the valley storage requirement.
• Acquisition of the required written consent and easements from all the affected property owners is unlikely and would result in an exceptional hardship.
• Granting of this variance will not result in additional threats to public safety or extraordinary public expense, create nuisances, cause fraud on or victimization of the public, or conflict with existing local laws.
• This variance will not be in violation of FEMA regulations.
FINANCIAL SUMMARY:
• No additional costs to the City or to developers are anticipated due to approval of this variance request.
BOARD OR COMMISSION RECOMMENDATION:
• N/A