Drainage and Stormwater Management

1 DelDOT Road Design manual July 2008 Highway Drainage and Stormwater Management 6-1 Chapter Six Drainage and Stormwater Management INTRODUCTION Adequate Drainage is essential in the design of highways since it affects the highway s serviceability and usable life, including the pavement s structural strength. If ponding on the traveled way occurs, hydroplaning becomes an important safety concern. Drainage design involves providing facilities that collect, transport and remove Stormwater from the highway.

2 The design must also consider the Stormwater reaching the roadway embankment through natural stream flow or manmade ditches. This chapter deals with Drainage policies, procedures and guidance to be followed in achieving cost-effective design and construction within DelDOT's Highway System. The information contained herein is compiled from various federal and national publications, textbooks, and Drainage manuals. The information provided is of a general nature with the inclusion of methods, criteria and references specifically applicable to DelDOT projects.

3 Source documents are listed in the introduction to each section. It is presumed that the designer is familiar with the basic theory and methods of analysis and design in both hydrology and hydraulics. The information provided herein will have to be supplemented with hard copies or on-line access to the referenced documents. The regulatory environment related to Drainage design is ever changing and continues to grow in complexity.

4 Engineers responsible for the planning and design of Drainage facilities must be familiar with Federal, state, county and local regulations, laws, and ordinances that may impact the design of storm drain systems. Many federal laws have implications that affect Drainage design. These include laws concerning: Flood insurance and construction in flood hazard areas, Navigation and construction in navigable waters, Water pollution control , Environmental protection, Protection of fish and wildlife, and Coastal zone Management .

5 Federal agencies formulate and promulgate rules and regulations to implement these laws. Highway hydraulic engineers should keep informed regarding proposed and final regulations. Some of the more significant federal laws affecting highway Drainage are: The Department of Transportation Act established the Department of Transportation and sets forth its powers, duties, and responsibilities to establish, coordinate, and maintain an effective administration of the transportation programs of the Federal Government.

6 Federal-Aid Highway Acts provide for the administration of the Federal-Aid Highway Program. Proposed Federal-aid projects must meet existing and probable future traffic needs and conditions in a manner conducive to safety, durability, and economy of maintenance, and must be DelDOT Road Design manual 6-2 Highway Drainage and Stormwater Management July 2008 designed and constructed according to standards best suited to accomplish this and to conform to the needs of each locality.

7 Federal-Aid Highway Act of 1970 provides for the establishment of general guidelines to ensure that possible adverse economic, social and environmental effects relating to any proposed Federal-aid project have been fully considered in developing the project. In compliance with the Act, the Federal Highway Administration (FHWA) issued process guidelines for the development of environmental action plans as contained in the Federal-Aid Highway Program manual (FHPM) and in 23 CFR 795 et seq.

8 Federal-Aid Highway Act of 1966 amended by the Act of 1970 requires the issuance of guidelines for minimizing possible soil erosion from highway construction. In compliance with these requirements, the FHWA issued guidelines that are applicable to all Federal-aid highway projects. These guidelines are included in the FHPM. Regulatory material is found in 23 CFR All Federal-aid projects shall conform to FHWA guidelines.

9 FHWA policy includes the following: FHWA Policy 23 CFR635 Subpart D General Material Requirements FHWA Policy 23 CFR650 Subpart A Location and Hydraulic Design of Encroachments on Floodplains establishes policy affecting any project that includes an encroachment on a base floodplain. FHWA Policy 23 CFR650 Subpart C National Bridge Inspection Standards defines the national standards for the proper safety inspection and evaluation of all highway bridges including the evaluation of bridges for scour susceptibility in accordance with the guidance in FHWA Technical Advisory FHWA Policy 23 CFR650 Subpart H Navigational Clearances for Bridges requires coordination with the United

10 States Coast Guard (USCG) and United States Army Corps of Engineers (USACE) in providing adequate vertical and horizontal clearance for navigation on navigable waterways. Other federal laws affecting hydraulic tasks, analyses, design, or construction include those formulated under the following legislative acts: The Coastal Zone Management Act of 1972 The Federal Water Pollution control Act (Clean Water Act) The Fish and Wildlife Act of 1956 The Fish and Wildlife Coordination Act The Flood Disaster Protection Act of 1973 The National Environmental Policy Act (NEPA) of 1969 The Rivers and Harbors Act (1899)