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he identified-during inspection. It is useful and often required as Cleaning part of a permit to keep a record of each inspection. A simple Cleaning of the CDS systems should be done during dry weather form for doing so is provided, conditions when no flow is entering the system. Cleanout of Access to the CDS unit is typically achieved through two manhole the CDS with a vacuum truck is generally the most effective and access covers. One opening allows for inspection and cleanout convenient method of excavating pollutants from the system. of the separation chamber(screen/cylinder)and isolated sump. Simply remove the manhole covers and insert the vacuum hose The other allows for inspection and deanout of sediment into the sump. The system should be completely drained down captured and retained behind the screen. For units possessing and the sump fully evacuated of sediment. The area outside the a sizable depth below grade(depth to pipe), a single manhole screen should be pumped out also if pollutant build-up exists in access point would allow both sump deanout and access behind this area. the screen. In installations where the risk of petroleum spills is small, liquid The CDS system should be cleaned when the level of sediment contaminants may not accumulate as quickly as sediment. has reached 75%of capacity in the isolated sump and/or when However,an oil or gasoline spill should be cleaned out an appreciable level of hydrocarbons and trash has accumulated. immediately. Motor oil and other hydrocarbons that accumulate If sorbent material is used, it should be replaced when significant on a more routine basis should be removed when an appreciable discoloration has occurred. Performance will not be impacted layer has been captured.To remove these pollutants,it may until 100%of the sump capacity is exceeded however it is be preferable to use adsorbent pads since they are usually less recommended that the system be cleaned prior to that for easier expensive to dispose than the oil/water emulsion that may be removal of sediment; The level of sediment is easily determined created by vacuuming the oily layer. Trash can be netted out if by measuring from finished grade down to the top of the you wish to separate it from the other pollutants. The screen sediment pile. To avoid underestimating the level of sediment should be power washed to ensure it is free of trash and debris. in the chamber; the measuring device must be lowered to the top of the sediment pile carefully. Finer, silty Manhole covers should be securely seated following cleaning p y ty particles at the top activities to prevent leakage of runoff into the system from above of the pile typically offer less resistance to the end of the rod and also to ensure proper safety precautions. Confined Space than larger particles toward the bottom of the pile. Once this Entry procedures need to be followed. Disposal of all material measurement is recorded,it should be compared to the as built removed from the CDS system should be done is accordance drawing for the unit to determine if the height of the sediment with local regulations. In many locations, disposal of evacuated pile off the bottom of the sump floor exceeds 75%of the total sediments may be handled in the same manner as disposal of height of isolated sump. sediments removed from catch basins or deep sump manholes. Check your local regulations for specific requirements on disposal. to 'rte€'i ` s' ' f 4., .'''4;: t..,; 1)01- -` ` ,: . 9 .' R .'k2 4,4 Ah r.A tea. ,„ i'4:, .� may' - ' _ p 6; ' s 1/ 9 ;fit ''.4 :„;.1 ,�, 1, o,,' ---. 5