Drainage Ditches and Culverts for Pads and Ranch Roads
Every site drainage job starts with two questions: where the water comes from, and where it can go. On a pad, a swale or ditch carries runoff away from the building area at a steady fall.
Where a road crosses a draw, a culvert lets storm water pass under the road base. A culvert too small for the flow sends water over the top and cuts the road away. On a wide, shallow draw, a low-water crossing lets the flow run across the road instead. Culverts on a new ranch or lease road go in with the road building work.
On development projects in Fort Worth, the city's stormwater review sets the design rules. Any ditch or culvert carrying more than 10 cubic feet per second needs a hydraulic model. The project's civil engineer runs that model, and we cut the ditch to the grades it sets.
What Goes Into Stock Tank and Pond Construction?
A stock tank is the Texas word for a farm pond. The USDA's pond handbook describes two kinds. An embankment pond holds water behind a dam built across a draw. An excavated pond is dug out of nearly level ground and holds a smaller supply.
The handbook rates clay and silty clay as excellent pond soils, and sandy clay as usually satisfactory. The drainage area above the tank has to be big enough to keep water in it through a drought. Too big, and storms call for costly overflow structures.
The site is cleared, and the topsoil is set aside for later. A core trench under the dam is filled with clay in thin layers, each compacted before the next. A spillway passes storm runoff around the dam before the water can top it. The handbook warns that a dam with too small a spillway will probably be destroyed in its first severe storm.
Detention and Erosion Control on Fort Worth Commercial Sites
Roofs and paving shed more water than open ground, and the city says that raises flooding risk. In Fort Worth, disturbing 1 acre or more calls for an approved grading permit and a stormwater drainage study. If downstream pipes and channels cannot carry the new flows, the developer can improve them or detain the water.
A detention basin holds that water and releases it through an outlet at pre-developed levels. We cut the basin and shape the swales that feed it to the engineer's grades. When a Fort Worth plan proposes detention, the city requires a storm water facilities maintenance agreement. This work often runs alongside site preparation for the building pads.
Erosion control is part of the rules on bigger sites. The TCEQ construction stormwater permit covers work that disturbs an acre or more of soil and drains to surface water. It calls for a stormwater pollution prevention plan before construction starts. The USDA handbook says grass planted soon after construction can protect disturbed ground from erosion.