Louisiana Administrative Code
Title 51 - PUBLIC HEALTH-SANITARY CODE
Part XIII - Sewage Disposal
Chapter 7 - Individual Sewerage Systems [formerly Chapter 13 Subpart D]
Subchapter B - Design and Construction Regulations [formerly Chapter 13 Appendix A]
Section XIII-723 - Sand Filter [formerly Section V of Appendix A]

A. [Formerly paragraph A:5.1 of Appendix A] Another alternative for the secondary treatment of septic tank effluent is a deep-type sand filter bed. Treatment in a sand filter bed is accomplished by the action of microorganisms in a sand bed in which the suspended solids of the septic tank effluent have been trapped by filtration. It is important that the sand bed remain aerobic throughout the treatment process. This is accomplished by exposing the sand surface to the air as much as possible on a continuous basis. Of course, the best way this can be done is to place no cover whatsoever over the sand bed. Since this is not aesthetically desirable for homes, a coarse gravel cover of clean, washed gravel, not to exceed 6 inches in depth over the bed is permitted. No other cover is acceptable. A filter bed system is shown in §1501. B.9 (Figure 9).

B. [Formerly paragraph A:5.2 of Appendix A] The sand filter bed is constructed by placing perforated pipe near the bottom of a rectangular area of the required size in a layer of gravel covered by a layer of coarse sand 24 inches deep. On top of this are placed distribution lines (perforated pipe) likewise encased in a layer of gravel [see §1501. B 10 (Figure 10)]. The septic tank effluent is distributed speedily in the gravel cover spreading over the top of the sand seeping slowly and vertically through the sand to the bottom layer of gravel to be carried away in the under drain line.

C. [Formerly paragraph A:5.3 of Appendix A] Sand filter beds are to be constructed with a minimum width of 12 feet and a minimum length of 25 feet. This minimum size filter bed is adequately sized for design flows of up to 400 gpd. For greater design flows, the required length shall be increased by eight feet for each additional 150 gpd or portion thereof.

D. [Formerly paragraph A:5.4 of Appendix A] The bed must be drained completely. This may require the bed to be raised above natural ground level.

E. [Formerly paragraph A:5.5 of Appendix A] To prevent sand infiltration into the underdrain, a layer of graded gravel must be placed over the underdrain line and the entire bottom of the filter bed. All gravel must be clean and washed.

F. [Formerly paragraph A:5.6 of Appendix A] Filter sand shall conform to the following standard specifications.

G. [Formerly paragraph A:5.7 of Appendix A] At least two distribution lines must be provided and they must be sloped 2 inches to 3 inches per 100 feet. The lines must be 4-inch diameter, 20-inch long farm tile, 2 feet to 3-feet lengths of vitrified clay bell-and-spigot sewer pipe laid with open joints, or perforated nonmetallic pipe meeting one of the standards cited in §719. M The ends of the distribution lines must be half-closed [see §1501. B 10 (Figure 10)].

H. [Formerly paragraph A:5.8 of Appendix A] Underdrain pipe materials are the same as those for the distribution pipe, however, the slope must be no less than 4 inches per 100 feet.

I. [Formerly paragraph A:5.9 of Appendix A] The filter bed must be appropriately protected from surface runoff water.

J. [Formerly paragraph A:5.10 of Appendix A] The filter bed must be located no less than 10 feet from the property line.

K. [Formerly paragraph A:5.11 of Appendix A] The location of the filter bed shall comply with minimum distance requirements from water wells, water lines, etc., as contained in Part XII of this Code.