Sand Filter

Technical Standards for Sand Filters

1. Sites for sand filters should be selected in the lower one third of the topographic cross section of the site within an area of poor infiltration. 

2. Area of storm water collection shall not exceed the area required to collect the down slope flow of no more than 5/6ths of the storage volume capacity of the filter. 

3. The sand filter shall consist of four parts consisting of: 

a. The delineator. This shall be a stone filter composed of rock of various sizes (3”, 4”, 5” & 6”) overlaying a3 mil porous weed barrier.

b. The sand lens which shall be sized to capture, filter and clean the design storm for the design storm and the drainage basin of the storm water facility.  A chemical filter barrier shall be used in the top six (6) inches of the sand lens. 

c. The concrete wall diffuser. This shall be an 8” reinforced concrete wall of variable depth and length which shall diffuse inflow.

d. Outflow shall be 4” to 8” pvc pipe connected to an outflow head wall overflowing into a rip rap water ramp.

e. Native grass filter a minimum of thirty-six (36) inch wide of native or ornamental  grasses such as andropogon, acymbopogon, bahiagrass, cynodon,  miscanthus, panicum, paspalum, pennisetum, tripsacum or vetiveria used to filter run off prior to introduction to the sand filter. 

4. Length and width and general sizing of the facility shall be as needed for the extent of the drainage area.

5. Grade drainage basin site with a broad shallow turf grass swale that will direct all run off to the facility.

6. Fortify and decorate the entry edge with paving units mortared to a concrete base at the edge of the sand filter to identity its presence in the landscape design.

7. Sand filter can be planted with drought tolerant palms, cycads, yucca or other desert plants.