When Denton County needed civil engineering services for analysis and design of the Oliver Creek Road Crossing, they called Pacheco Koch. The project was tailored to meet Denton County’s budget constraints through two separate phases of design. The first phase prepared a detailed hydrologic model of the watershed and a preliminary hydraulic analysis of the road crossing, with alternative analyses and probable construction cost estimates. The second phase provided a detailed hydraulic analysis, Letter of Map Revision (LOMR), and final design plans.
The second phase was expedited to meet county requirements to encumber funds before fiscal year end. Vehicular access to this existing low-water crossing was closed due to damage caused during a recent storm event. A detailed hydrologic model was developed for approximately 58 square miles of watershed located in Denton and Wise counties. Three existing NRCS lakes were modeled in the analysis. The model incorporated a point rainfall reduction and included modified puls routing for nearly 19 miles of stream to simulate the significant attenuation effects related to valley storage. An unsteady hydraulic model was used to quickly develop the storage-discharge relationship within each reach. Discharges for the 1-, 2-, 5-, 10-, 25-, 50-, and 100-year recurrence interval storms were determined, and a hydraulic analysis was prepared for approximately 1.5 miles of Zone A designated floodplain. Construction alternatives were developed for multiple recurrence intervals.
The project also included delineation of Jurisdictional Waters of the U.S., construction permitting through the U.S. Army Corps of Engineers, preparation of a LOMR through FEMA, development of culvert design plans, traffic control planning, and utility coordination, as well as bidding and construction phase services.