OHA Drinking Water Services
OHA Drinking Water Services
Contact Report Details

PWS ID: OR41 00055
Who Was Contacted and Phone: Gary McLauchlin (503) 325-3524
Contact Date: 06/19/2009
Contacted By: HOFELD, EVAN (REGION 1)
Contact Method/Location: Office
Reasons: SWTR
Details: SUMMARY: Answered questions about slow sand media DETAILS: I sent an e-mail to Gary at gmc@astoria.or.us about slow sand filter media depth. Filter media should conform to the standards in AWWA B100, which specifies the quality but not the depth. Our rules do not specify a depth, but I sent three documents that should have helped. I sent a pdf called 9205-00055 Slow Sand Specs from the bid documents for modifications to Astorias filters in 1992 - I copied the cover and the section pertaining to the media - it shows a table of depths for the silica sand and gravel and 18 inches of sand media, for a total depth of 41" (I think there may be a typo in it, because is says 41 inches of fine media, but the top paragraph of page 4 indicates to mark a sand media depth of 18 inches and the sum of the gravel depths in the table and 18 inches is equal to 41 inches). The range in guidelines for minimum fine media depth seems to be 30-80 cm (1.0-2.6 ft) per the 1991 AWWA Slow Sand filter design manual (excerpt attached as a pdf called Slow Sand Bed Depth). Chapter 3 on page 18 of the other attached PDF document from the Washington Dept of Health had detailed information on slow sand design. ACTION NEEDED: System to call if further questions.

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