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2.3.3 Elevated Sand Trench  (Title 25. Environmental Protection, Chapter 73,  Section 73.55)


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In-ground version of a trench system.  The
elevated sand trench system is a high-breed system that is basically an elevated mound with a trench construction.


System Highlights (General Highlight of Characteristics Required for this System- It is critical that you review the PADEP regulations and any local agency regulations regarding the siting and use of this system.   In general, these systems have found widespread use in Pennsylvania, because of the presence of fragipans, perched water tables, and shallow depths to bedrock and high permeability materials. These systems can be used when:

1. The depth to the limiting zone occurs at less 20 inches to less than 48 inches below the mineral soil surface.  The system then requires that approved sand be used to create a minimum of 4 feet of satisfactory material between the bottom of the aggregate and the top of the limiting zone, but a 1 foot minimum of sand is required in all elevated sand mound systems.

2.Maximum Slope of undisturbed soil for an inground trench is 25%.

3.The average percolation rate, as determined, by conventional test, see Section 73.15, yields a percolation rate of  3 to 180 min/inch.

4.The sand will be placed from the upslope side of the bed using lightweight equipment, the slope of the sand not directly beneath the aggregate area shall be approximately 50%, and the top of the sand directly beneath the aggregate shall be level to a tolerance of +2 inches per 100 feet.   The bed should be surrounded by suitable berm material and the width of this berm shall be a minimum of 3 feet at the top of the aggregate.

5.Regarding construction, the system design will meet  Section 73.52 (trenches) with exceptions and additional specifications.

6.When a mound system with trenches is used, the area between the individual trenches shall be filled with mineral soil.  A minimum distance of 5 feet shall separate sands of individual trenches.  This measurement shall be from the toe of the sand.

For more details, see Chapter 73, Section 73.55.