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100. ,_ w� ,- Maintenance * The CDS system should be inspected at regular intervals and `°"; maintained when necessary to ensure optimum performance. „ , ,..a , The rate at which the system collects pollutants will depend more heavily on site activities than the size of the unit,e.g.,unstable soils or heavy winter sanding will cause the grit chamber to fill { --;tAt more quickly but regular sweeping of paved surfaces will slow ''ice 130; i accumulation, 0,00 & 00% 00% 100% t 140% Inspection %Design.Fkrwftate Figure 2. CDS stormwater treatment predictive performance for Inspection is the key to effective maintenance arid is easily various particle gradations as a function of operating rate. performed. Pollutant deposition arid transport may vary from year to year and regular inspections will help insure that the Many regulatory jurisdictions set a performance standard for system is cleaned out at the appropriate time. At a minimum, hydrodynamic devices by stating that the devices shall be capable inspections should be performed twice per year(i.e, spring and of achieving an 80%removal efficiency for particles having a fall)however more frequent inspections may be necessary in mean particle size(d50)of 125 microns(VVADOE,2008), The climates where winter sanding operations may lead to rapid model can be used to calculate the expected performance of such accumulations,or in equipment washdown areas Additionally, a PSD(shown in Figure 3). Supported by the laboratory data,the installations should be inspected more frequently where excessive model indicates(Figure 4)that the CDS system with 2400 micron amounts of trash are expected. screen achieves approximately 80%removal at 100%of design flow rate,for this particle size distribution(d50 = 125 pm). The visual inspection should ascertain that the system components are in working order and that there are no blockages or obstructions to inlet and/or separation screen. The inspection should also identify evidence of vector infestation .100 and accumulations of hydrocarbons,trash, and sediment in the °'" y a ' q "`' , , .,;:x system_ Measuring pollutant accumulation can be done with a calibrated dipstick,tape measure or other measuring instrument: y� -:. , , , ,:3 .2. ,„ If sorbent material is used for enhanced removal of hydrocarbons " then the level of discoloration of the sorbent material should also 40 , b '10 1 'taaf tom: Figure 3. PSD with d50 — 125 microns, used to model performance for Ecology submittal. CDS 6t PeriberrIonce for ., - ,, _ % '4' r a i a ; q ar d #; ALL. a 40%- 00% IX% 120% '140% . : � Figure 4. Modeled performance for CDS unit with 2400 microns '-r screen, using Ecology PSD:; . 14 _ .M -.• ';',f.';'..;':-',,„.';.'•!:,.'-':',";;:.,'-';'.. 'a 'fi" 5 ..0.."a4{ k p 4