DECLASSIFIED Authority SECRET VOLUUE I Ph-YS I CAL DAf iAGE IIIROSIJIMA J APAI · Prepar ed by Ma j or No l a nd Varl ey SECRET rvrv D ¥1 c S5 • SECR REPORT BY MAJOR NOLAND VARLEY MANHATTAN DISTRI CT CORPS OF ENGINEERS -- DECLASSIFIED Authority f J N D ¥100 SEC E • ESTiulAT- D P AK BLA ST P ESSURE The f ollowing tabul a tion i s f ro a r epor t by Dr r G Penney Distance - Fe et f rom Zero Po i nt Peak Pr e s sur e Pe a k Pressw e Lbs Sq Inch Lbs Sq Ft 0 35 5040 600 25 3 60 0 1 000 20 2 880 2 100 15 4 2218 3 2 00 9 2 132 5 3 8 00 6 6 950 4 100 5 5 7 92 5 0 00 3 2 461 1 2 000 0 5 72 1 5 00 0 0 2s 40 - -DE CLASS Authority rvrv D _$5_ 1 SE • DECLASSIFIED Authority rvrv D ¥1 c S5 portion of the pattern in cotton prints was often burned or charred leaving the wh ite or light colored portion of t h e pattern only slightly scorched METEOROLOGICAL EFFECTS The Japanese reported that a black shower fell ten minutes after the explosion A normal rain fell nea r the center of t h e city in the afternoon and in the western part of the city in t h e late afternoon High winds were reported to have blown across the city during the aft ernoon and night of August 6 Whirlwinds of consider able velocity were a lso rep9rted by t h e Japanese POPULATION The population of Hirosh ima at the t ime of the explosion was probab l y between 250 000 and 320 000 Reliable fi gures were not a va ilable Military personnel in Hirosh i ma a t t h e t ime of t h e ex plosi on was repor t ed b y the Tok oy o Li a ison Offi ce of t h e J apane s e Army t o be appr oximately 24 000 DECLASSIFIED SECRET Authority r J J D ¥10055 Mechanical injuries nesulted from the widespread collapse of buildings and from contact with high velocity secondary missiles Collapse of fr ame building s top heavy with clay tile roofing resulted in heavy casualties Detachable material in reinforced concrete buildin0s wa s torn loose to form high velocity missiles Suspended ceilings collapsed with explosive force due to compression of the air in the closed space above the ceiling The basements of reinforced concrete build i n g s formed the only areas of safety Persons in the str e ets had li t tle chance of survival within one mile of t h e explosion The fir e s of secondary origin that swept the devastated area prevented the rescue of persons trapped in the debr is of collapsed buildings ECR SECRE • DECLASSIFIED Authority rvrv D ¥1 DOSS PUBLIC UTILITIES wat er Supply and Distribution Systeme Underground wa t er main s suffered only minor dama ge from the blast Many fire hydrants we re broken off By falling debris Service lines to buildings were broken off above ground due o collapse of the buildings The ma in Filtration Plant located one and th J 'ee fourths mile north of zero point suffered only minor damage Some recording flow meters were put out of operation by the blast Chlori•ation equipment was not operatlng since the supply of ch lorine ga s had been exhausted Distribution was b y direct pressure to the mains Electric Power Supply was from a Steam Plant located outside the city Three substations in Hiroshima were put out of a ction and transmission lines were broken by failure of power line poles EC ET DECLASSIFIED Authority rvrvD 'Jv 00 55 Gas Supplies The gas-works located 1 2 mile southeast of zero po i nt was seriously dama g ed a s shown in pictures included with t h is report It will be necessary to rebu ld t h e plant b e fore it can be placed back in operation The underground distribution system suffered little dama g e Gas pressure failed immed- iately after the explosion since the g as-holders were ri pped open by the blast Sewerag e System Ra w sewerag e was d i charg ed directly into the Ota river Sewer ma i n suffered little d ama g e T I HIROSHIMA PROFILE I 0 1000 2000 3000 DISTANCE FROM ZERO IN FEET 4000 7000