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Silver Lake Plaza <br />Table V-4.5.2(14) Maintenance Standards - Sand Filters (Below <br />GroundlEnclosed) (continued) <br />Maintenance <br />Defect <br />Condition When Main- <br />Results Expected When <br />Maintenance is Per- <br />tenance is Needed <br />formed <br />formed <br />area. A specified % of the <br />vault surface area must <br />provide ventilation to the <br />vault interior (see design <br />specifications). <br />Cracks wider than 1/2-inch <br />or evidence of soil particles <br />entering the structure <br />Vault replaced or repairs <br />Vault Structure <br />through the cracks, or main- <br />made so that vault meets <br />Damaged; <br />tenance/inspection per- <br />design specifications and <br />Includes Cracks <br />sonnel determine that the <br />is structurally sound. <br />in Walls, Bot- <br />vault is not structurally <br />tom, Damage to <br />sound. <br />Vault repaired so that no <br />Frame and/or <br />Cracks widerthan 1/2-inch <br />cracks exist wider than <br />1/4-inch at the joint of the <br />Top Slab. <br />at the joint of any inlet/outlet <br />inlet/outlet pipe. <br />pipe or evidence of soil <br />particles entering through <br />the cracks. <br />Baffles or walls corroding, <br />Baffles/Internal <br />cracking, warping and/or <br />Baffles repaired or <br />walls <br />showing signs of failure as <br />replaced to specifications. <br />determined by main- <br />tenance/inspection person. <br />Ladder is corroded or deteri- <br />Ladder replaced or <br />orated, not functioning prop- <br />repaired to specifications, <br />Access Ladder <br />erly, not securely attached to <br />and is safe to use as <br />Damaged <br />structure wall, missing <br />determined by inspection <br />rungs, cracks, and mis- <br />personnel. <br />aligned. <br />Basic sand filter maintenance criteria: <br />Inspections of sand filters and pretreatment systems should be conducted every 6 months and <br />after storm events as needed during the first year of operation, and annually thereafter if filter <br />perfonns as designed. Repairs should be performed as necessary. <br />Suggestions for maintenance include: <br />• Accumulated silt, and debris on top of the sand filter should be removed when their depth <br />exceeds 1/2-inch. The silt should be scraped off during dry periods with steel rakes or other <br />devices. Once sediment is removed, the design permeability of the filtration media can <br />typically be restored by then striating the surface layer of the media. Finer sediments that <br />have penetrated deeper into the filtration media can reduce the permeability to unacceptable <br />levels, necessitating replacement of some or all of the sand. <br />WESTERN ENGINEERS, INC. 41 PROJECT: 15-1415-A <br />