La. Admin. Code tit. 70 § II-525

Current through Register Vol. 50, No. 11, November 20, 2024

Section II-525 - Drainage Related Actions within or Adjacent to State Highway

A. General Requirements

1. All construction activities within state highway rights-of-way or servitudes shall conform to latest DOTD standards. Typical sections of ramps, driveways, intersecting streets, etc., shall generally conform to the standards under which the roadway was built. The design of drainage structures, such as side-drains, pipe drops, cross-drains, storm sewer systems, etc., shall be according to current standards as indicated in the DOTD's Hydraulics Manual; the materials must also conform to current standards. Extensive construction activities are subject to erosion from flowing water. Seeding, fertilizing and watering of denuded areas, using current standards, are required.

2. Diversion of additional drainage area to highway ditches, side-drains, crossdrains, bridges and storm sewer systems will not be allowed unless acceptable compensating or mitigating features are provided. Significant modifications of roadside ditches which adversely affect safety, drainage, maintainability or esthetics will not be allowed. The applicant should include sufficient information so that the required evaluations can be performed.

B. Roadside Ditches. Permit requests for tie-in of drainage systems to highway roadside or lateral ditches will be evaluated per individual request.

1. Examples of significant section alteration would be:

a. a significantly deeper ditch;

b. steeper side-slopes;

c. narrowing the existing shoulder;

d. significantly flatter ditch grades, etc.; or

e. any change which would have a significant adverse affect on the safety of maintenance personnel and the traveling public, maintainability of the roadside, capacity of the roadside ditch, or esthetics.

2. Examples of compensatory or mitigating proposals would be:

a. to enclose the roadside ditch using a properly designed swale ditch/storm sewer system; or

b. to modify the existing ditch to meet current standards.

3. The latter method usually results in wider shoulders, flatter slopes and often requires additional right-of-way. Current design methods will be used to evaluate the ability of existing drainage features to accept flow modifications requested by applicant. The applicant should include sufficient information so that the permit request may be evaluated. Required information may consist of drainage maps, plan-profile sheets, cross-sections, etc.

C. Storm Drain Systems

1. Generally, proposed tie-ins to existing highway storm drain systems will not be allowed if additional drainage area is being diverted to the system. That is, if the total proposed drainage area is greater than the existing drainage area, permission for a tie-in will usually be denied. Exceptions may be granted when it can be shown that there are compensatory or mitigating features in the proposal. An example of this could be where another highway system is overloaded and the proposed diversion eases the problem without creating a significant overload to the system to which the tie-in is requested. In general, tie-ins will be allowed if the drainage area served is within the original design drainage area. The construction of the tie-in shall be according to current standards.

2. Parallel storm drain trunk lines may be allowed within highway right-of-way if it can be shown that the proposed trunk line benefits highway drainage. An example of this would be if the proposed trunk line serves a drainage area previously draining to the highway drainage system. Another condition which must be satisfied is that there be no interference with utilities or highway features.

3. The application should include sufficient information so that the permit request may be evaluated. Required information may consist of drainage maps, plan-profile sheets, cross-sections, etc.

D. Driveways in Roadside Ditch Areas

1. Most driveways (ramps) require a drainage structure (side-drain) underneath them to convey roadside ditch flows. A ramp located at a divide in roadside ditch flow direction may be built without a side-drain, and is called a dry ramp. Two consecutive dry ramps are not allowed.

2. Recommended minimum side-drain sizes are based on current DOTD design standards. The property owner may use side-drains with capacities greater than the recommended minimum.

3. The applicant should include sufficient information so that the permit request may be evaluated. A rough sketch locating the proposed ramp is a minimum requirement. Additional helpful information would be the drainage area contributing to the side-drain.

E. Driveways in Swale Ditch Storm Drain System Areas

1. A driveway installed in areas where highway drainage is provided by a swale ditch/storm drain system may take one of two forms. Each is designed to continue existing drainage.

2. The first option is to construct the driveway to cross-section of the swale. Where swales are shallow, this is a practical solution. Swale drainage must be continued across the driveway.

3. The second solution is to construct a catch basin upstream of the driveway to intercept swale drainage. Drive profiles need not follow the swale ditch shape and catch basin design must be approved.

La. Admin. Code tit. 70, § II-525

Promulgated by the Department of Transportation and Development, Utility and Permit Section, LR 20:317 (March 1994).

AUTHORITY NOTE: Promulgated in accordance with R.S. 48:381-382, 48:193, 48:344, 38:2223.