Page 15 - Section4.1.1-SWPPPCutSheet-FiltrexxSedimentControl

338 | Filtrexx ® Low Impact Design Manual | Version 8.0

6. Installation of Concrete washouts shall ensure that the containment area within the Concrete washout is suffcient to allow for receiving water to properly fow through the flter Concrete washout fltration system.

7. Stakes shall be installed through the middle of the Concrete washout on 5 ft (1.5m) centers, using 2 in (50mm) by 2 in (50mm) by 3 ft (1m) wooden stakes.

8. Staking depth for sand and silt loam soils shall be 12 in (300mm), and 8 in (200mm) for clay soils.

9. Standard diameter size of Concrete washouts for concrete washouts is 18 in (450mm). For applications where rate or volume of contami- nated water addition is high the Engineer may specify 24 in (600mm) or 32 in (800m) diameter Concrete washouts, a stack design, or an equilateral triangle or pyramid design.

10. If stack or pyramid design is specifed, Concrete washout Soxx tm should decrease in diameter with each layer of Concrete washout Soxx tm .

11. Concrete washouts may be installed on top of impermeable mats or membranes to prevent percolation of contaminated water into soil. Local ordinances may require the use of additives to reduce ph contamination in runoff. 1 2. Concrete washouts shall not be placed near concentrated or high sheet fows of storm runoff which may compromise the structural base of the Concrete washout.

13. Vegetated Concrete washouts may be seeded at the time of manufacture and installation to create a contained ‘green or living bio-flter’. These may be left intact once construction phase is complete. The appropriate seed mix, live stakes, and/or sprigs shall be specifed by the Engineer.

14. Concrete washouts installed on paved surfaces should be stabilized along the outer circumference using concrete blocks for structural support.

INSPECTION and MAINTENANCE

Routine inspection should be conducted within 24 hrs of a runoff event or as designated by the regulating authority. Concrete washouts should be regularly inspected to make sure they maintain their shape and are producing adequate hydraulic fow-through and solids removal. If rainfall is excessive, additional Concrete washouts may be required to contain the added water volume. Water height within the Concrete washouts should remain 4 in below the lowest point of the rim to allow for storm water volume additions. If overfow, undercutting, or leaking between Concrete washouts occurs,

maintenance should be conducted immediately.

1. The Contractor shall maintain the Concrete washouts in a functional condition at all times and it shall be routinely inspected.

2. If a Concrete washout has been damaged, it shall be repaired, or replaced if beyond repair.

3. The Contractor shall remove solids or fltrate from the inside of the Concrete washout when solids accumulation has reached 1/2 of the effective height of the Concrete washout, or as directed by the Engineer. As an alternative, another Concrete washout may be installed on top of, or in a pyramid design to increase the containment capacity of the Concrete washout.

4. If Concrete washouts become clogged with debris or solids, they shall be maintained so as to assure proper hydraulic fow through. Overfow or undercutting of contaminated water is not acceptable.

5. If minor undercutting occurs, the areas may be plugged with sand, soil or additional

FilterMedia tm . If undercutting continues, a new Concrete washout should be installed and leveling or minor grading of ground surface may be required to increase surface contact with Concrete washout.

6. Concrete washouts shall be maintained until contaminated water has fully percolated through the device.

7. The FilterMedia tm and fltrate may be dispersed on site once solids separation is complete only if there are no concerns with soil and water contamination, or as determined by the Engineer.