Document qavODLQ2aJgyObYvmVejabvjj

December 1940 Memorandum for Tank: Cleaning Mile Ament the matter of what constituted a clean tank:, data from the two samples of Mr. Siebenthaler are appended. It should be noted that only high pressure mater was used in cleaning the tank and the amounts of material, namely 81 grams of scale and 235 grams of sludge, are within reasonable limits of what one might expect after such a cleaning operation. The concentrations of organic lead mere lot? in both instances and it is v;orth noting that the absolute amounts of organic lead in the scale mere less than 0.2 ng. in the entire ICO sc. feet of surface and about 1.3 mg. from the entire 100 sa. feet of bottom plate. These are less chan the amounts necessary to create unsafe concentrations in 10 cu. m. of air. Looking at the results another nay, 2C0 times the amounts of organic lead found in these samples have been obtained in samples from other tanks and in one instance 1,000 times these concentrations were encountered. Therefore, slightly more than 1 gram of lead might be present under exceptional circumstances in the amounts of sludge left remaining after Uilorough cleaning on 100 so;, feet of tank space, .assuming that all of this were tc evaporate into an enclosed place without ventilation, lethal exposure could be gotten in one day*s work. This situation would probably be possible only in a small tank, for example, a 1C' x 30* with a single top .manhole. ' ..In the case of larger tanks with more than one opening, any movement of air mould of course tend to reduce the oon- centration, 0022386 2- ?rcru the present state cf our knowledge then there is a possibility that in about 1 in ICO or :;iore tanks a situation could occur in which the tank was thoroughly cleaned and then closed and allowed to stand for days or weeks, at the end of which tine, men 'would enter the tank for purposes of repair and be poisoned. Alargo number of conditions, such as the above, would have to be net, particularly the ones specifying complete absence cf ventilation and full day's exposure under identical conditions, and probably more importantly, a rate of volatilization of organic lead from flu sludge sufficiently rapid to effect saturation in the time allotted. Ihis would occur probably only if the organic compounds were pure tetraethyl lead and they did net undergo any decomposition in the period of standing. In line with this, it would be advantageous to know the rate of evaporation of organic lead from sludge and the influence of ventilation on this, 'dork on this is i ow in progress. 'sVillard Machie, h. D. 0022387