Stormwater drainage for temporary conditions during construction where the permanent drainage has not yet been constructed or connected should be designed using the guidance in TxDOT’s . The expected capacity for which the temporary system should be designed will depend on the expected duration of the temporary condition. A conservative approach for typical construction phases is to assume a rainfall event with a 50% Annual Exceedance Probability, or a 2-year Annual Recurrence Interval.

Temporary drainage should be designed using positive drainage in an TCP phases and should not assume the contractor will use pumps to drain low points. Design of the temporary drainage should be coordinated with the design of the Storm Water Pollution Prevention Plan (SWP3).

Refer to TxDOT’s , Chapter 8, Section 6 – Special Applications for discussion on risk assessment during construction.