Chapter 3: Types of Documentation
Anchor: #i1006893Section 1: Types of Documentation
Anchor: #i1006898Documentation Categories
TxDOT hydraulic facility analyses and design generally fall into the following basic categories:
- Parameter and criteria considerations -- Documentation of parameter and criteria considerations includes data source identification, evaluation of data, assessments of the reliability of data, what decisions were made and why, qualifying statements such as limitations and disclaimers, and design values comprising the set of parameters and criteria that govern the design. Design parameters define the limits of the facility design. For example, in sizing a structure, design parameters include economically available shapes, environmentally suitable materials, and physical geometric limitations. The standards of design development are the design criteria. Examples include allowable headwater (for a culvert), allowable through-bridge velocity (for a bridge), and maximum water elevation in a pump station sump. Both design parameters and criteria are established from the unique characteristics of the design site and situation. These items should be fully documented for the design of TxDOT drainage facilities.
- Federal and state regulatory criteria -- (See Chapter 2.)
- TxDOT policy or coordination with other policy – TxDOT policy represents a significant basis of design of any drainage facility. Chapter 2 addresses TxDOT drainage-related policy. In cases where TxDOT policy conflicts or differs with policy of an outside entity, include qualifying statements and explanations in the documentation. Note that federal and state regulatory criteria have the force of law with which TxDOT must comply. Anchor: #i998540
- Hydrology and hydraulic analyses -- Documentation of the hydrologic and hydraulic analyses includes the assumptions, judgments, decisions, computations, and plans, profiles, and details.
Carefully identify, consider, and evaluate data sources used during the design process. In a conflict among data from different sources, evaluate the conflicting data to determine its relevance and usefulness.
Make subjective selections, decisions, and assignments throughout TxDOT drainage design procedures as part of the engineering design process. When subjectivity is necessary, document the qualifying statements about the selection process. For example, the assignment of a runoff coefficient for use in the rational method of estimating peak discharge is a subjective assignment based upon current and projected watershed characteristics. You should systematically assess those characteristics. However, in order to assign an appropriate runoff coefficient, you must make judgments regarding future watershed characteristics. Include the design considerations leading to those judgments in the files as qualifying statements.