Rule 15-18-77-5.5.15 - Expanded Polystyrene (EPS) Aggregate Systems1. General: The EPS Aggregate system utilizes bundles of expanded polystyrene aggregate to replace rock aggregate in a subsurface disposal system. Effluent is distributed via a 4 inch perforated pipe incorporated into the center of one EPS bundle. System configurations of multiple bundles will incorporate one bundle run containing the 4 inch perforated pipe in conjunction with bundles containing only EPS aggregate. This 4 inch perforated pipe receives the treated effluent for distribution throughout the trench. The expanded polystyrene aggregate must be contained in a material that is resistant to the effects of wastewater, will prevent the loss of aggregate from the container and strong enough to retain the shape of the bundles during system installation and backfilling. All EPS Aggregate Systems must be installed by a factory-trained installer that is an authorized representative of the manufacturer.2. Construction a. The EPS Aggregate System absorption trenches shall be a minimum of 24 inches and a maximum of 36 inches in width. b. The bottom of the trenches and the distribution lines shall have a grade from level to no greater than two inches fall per 100 feet.c. The grade shall be measured from the trench bottom and not the effluent distribution line encased in the EPS bundle.d. The EPS Aggregate system shall be covered with an approved cover material before backfilling. Covering material shall consist of craft paper or other bio-degradable product approved and/or supplied by the manufacturer.3. Distribution of Effluent [EPS Aggregate System] a. When a change in elevation of the disposal trench is required, a distribution box, connecting lateral or crossover must be used. At the point where a crossover line leaves a lateral, the trench for the crossover line shall be dug no deeper than the top of the distribution pipe in the preceding trench so that an undisturbed block of earth will remain in place for the full depth of the system [Figure 2]. The invert of the crossover must be at least four inches lower than the invert of the septic tank outlet line. b. Distribution boxes may be used to connect the effluent line to the effluent distribution lines. The distribution box shall be level and supply all lines equally. Field lines must be equal lengths when served by one distribution box. Non-perforated rigid pipe shall exit the distribution box for a minimum of five feet at level grade before the effluent distribution line (perforations) begins.4. Absorption Beds [EPS Aggregate Systems]: Absorption beds may be constructed using the EPS Aggregate system. a. Absorption beds and trenches should be located a minimum of 10 feet from any trees.b. The amount of linear footage required for EPS horizontal systems shall be the same as for trench configurations [Table V]. The bottom of the bed should have a relatively level grade; the grade within the bed shall not exceed the grade allowed for EPS trench installations. EPS triangular systems shall not be used in bed configurations.c. The EPS bundles shall be placed side by side in the bed. The number of bundles will depend on the lineal footage required and the width of the bed to be constructed.d. Care should be taken to prevent heavy machinery from damaging the bed during backfilling.e. The effluent must be equally distributed to the bed by means of a distribution box or with a pipe manifold.5. Sizing a. EPS Aggregate systems shall be sized in accordance Table6. Homeowners may install 1-14 configuration EPS, provided that all applicable regulations of the Department are observed15 Miss. Code. R. 18-77-5.5.15