Page 12 - Section3.2-FiltrexxLockDownNetting

Sand has been widely used as a water fltration media for many applications. Filtrexx ® Filtration Sand may be blended with the FilterMedia tm or applied in the feld to any of the following Filtrexx ® sediment control and fltration practices, including Sediment control, Check dams, Concrete washouts, Slope interruption, and Filtration system baffes. It is specifcally used to further reduce suspended solids and turbidity in storm runoff . Filtration Sand should not be used without one of these Filtrexx ® practices but may be used in any landscape and/or near receiving waters. For optimum performance this Support Practice tm may be applied immediately upslope and/or along the inner circumference of the Filtrexx ® management practice or blended with Filtrexx ® FilterMedia tm prior to FilterSoxx tm installation. Filtration Sand grade used for this application shall be 50% #20 and 50% #30 grade sand (medium coarse/coarse -all purpose).

Sand is a material that can be used for physical fltration of solids from water and storm water. Used with FilterMedia tm it can reduce suspended solids and turbidity of runoff when applied with Sediment control, Check dams, and Slope interruption, or solids content of storm water and effuents where Concrete washouts and Filtration system baffes are utilized. Filtration Sand is an inert material that when blended to FilterMedia tm can reduce porosity and permeability within the FilterSoxx tm . Reducing porosity and permeability will reduce the ability of solids to permeate the flter and will decrease the ability of smaller sediments (and solids), which normally contribute to suspended solids and turbidity in storm water runoff, to migrate through macro pores in the FilterMedia-FilterSoxx tm matrix.

By blending Filtration Sand with FilterMedia tm , hydraulic fow through rates will be reduced and water ponding may increase. This may be desirable in applications where low hydraulic fow through rate is desirable or unimportant, or when FilterMedia tm is too coarse and hydraulic fow through rates are too high.

According to independent testing by the Soil Control Lab, Inc., in Watsonville, CA, blending the specifed Filtration Sand with FilterMedia tm at 6% (v/v) has been shown to increase turbidity reduction performance from 26% to 53% and suspended solids removal from 64% to 71%. Increasing the blend percentage to 25% (v/v) has been shown to increase turbidity reduction from 26% to 65% and suspended solids removal from 64% to 82%.

Alternatively, if a 1 in (2.5 cm) high line of Filtration Sand is applied to the upslope or inside edge of the FilterSoxx tm suspended solids and turbidity reduction from runoff or solids-laden effuent can also be attained. This application may also reduce hydraulic fow through rates, particularly under low fow conditions. This may be desirable in applications where low a hydraulic fow through rate is desirable or unimportant, or when FilterMedia tm is too coarse and hydraulic fow through rates are too high. This application may also function to minimize undercutting of the FilterSoxx tm .

According to independent testing by the Soil Control Lab, Inc., in Watsonville, CA, adding a 1 in (2.5 cm) high line of the specifed Filtration Sand to the upslope or inside edge of the FilterSoxx tm has been shown to increase turbidity reduction performance from 26% to 65% and suspended solids removal from 64% to 89%. Similarly, the USDA-ARS has reported a 10% increase in TSS removal effciency when adding a line of Filtration Sand to FilterSoxx tm .