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No. 3 — Closed Detention Systems (Tanks/Vaults) <br />Maintenance <br />Component <br />Defect <br />Conditions When Maintenance is Needed <br />Results Expected <br />When Maintenance is <br />Performed <br />Storage Area <br />Plugged Air Vents <br />One-half of the cross section of a vent is <br />blocked at any point or the vent is damaged. <br />Vents open and <br />functioning. <br />Debris and Sediment <br />Accumulated sediment depth exceeds 10% <br />of the diameter of the storage area for 1/2 <br />All sediment and <br />debris removed from <br />length of storage vault or any point depth <br />storage area. <br />exceeds 15% of diameter. <br />(Example: 72-inch storage tank would <br />require cleaning when sediment reaches <br />depth of 7 inches for more than 1/2 length of <br />tank.) <br />Joints Between <br />Tank/Pipe Section <br />Any openings or voids allowing material to <br />be transported into facility. <br />(Will require engineering analysis to <br />determine structural stability). <br />All joint between <br />tank/pipe sections <br />are sealed. <br />Tank Pipe Bent Out <br />of Shape <br />Any part of tank/pipe is bent out of shape <br />more than 10% of its design shape. (Review <br />required by engineer to determine structural <br />Tank/pipe repaired or <br />replaced to design. <br />stability). <br />Vault Structure <br />Includes Cracks in <br />Wall, Bottom, <br />Damage to Frame <br />and/or Top Slab <br />Cracks wider than 1/2-inch and any <br />evidence of soil particles entering the <br />structure through the cracks, or <br />maintenance/inspection personnel <br />determines that the vault is not structurally <br />sound. <br />Vault replaced or <br />repaired to design <br />specifications and is <br />structurally sound. <br />Cracks wider than 1/2-inch at the joint of any <br />inlet/outlet pipe or any evidence of soil <br />particles entering the vault through the walls. <br />No cracks more than <br />1/4-inch wide at the <br />joint of the inlet/outlet <br />pipe. <br />Manhole <br />Cover Not in Place <br />Cover is missing or only partially in place. <br />Any open manhole requires maintenance. <br />Manhole is closed. <br />Locking Mechanism <br />Not Working <br />Mechanism cannot be opened by one <br />maintenance person with proper tools. Bolts <br />into frame have less than 1/2 inch of thread <br />Mechanism opens <br />with proper tools. <br />(may not apply to self-locking lids). <br />Cover Difficult to <br />Remove <br />One maintenance person cannot remove lid <br />after applying normal lifting pressure. Intent <br />is to keep cover from sealing off access to <br />maintenance. <br />Cover can be <br />removed and <br />reinstalled by one <br />maintenance person. <br />Ladder Rungs Unsafe <br />Ladder is unsafe due to missing rungs, <br />misalignment, not securely attached to <br />structure wall, rust, or cracks. <br />Ladder meets design <br />standards. Allows <br />maintenance person <br />safe access. <br />Catch Basins <br />See "Catch Basins" <br />(No. 5) <br />See "Catch Basins" (No. 5). <br />See "Catch Basins" <br />(No. 5). <br />Volume V — Runoff Treatment BMPs — December 2014 <br />4-36 <br />