Concrete Ship Constructors of National City,
Cal., U.S.A.

 B7-A2 type

MC Hull Nos  634-638                      Yard Nos 1-5
                        1220-1236                                       6-22

These concrete barges were first envisaged in 1941, when it was becoming apparent that something would have to be done to increase the movement of petroleum products from the Texas oil area to the North-Eastern United States.
The proposal to build a pipeline had not been favoured by shipbuilders and by the end of 1941, when the USA had been drawn into the war, the shortage of steel caused the Maritime Commission to recommend that concrete tow barges be built for the purpose.
When the first plans were drawn up it was thought that no quarters for crews needed to be provided, but the Bureau of Marine Inspection and Navigation decided that the barges must have crews to prevent them becoming navigational hazards in the event of casualty. The provision of crew quarters made it necessary to add not only a deck house (aft) but other equipment, including lifesaving gear and wartime defence features. Two small 45-hp diesel engines were installed in a midship house for pumps, lighting, winches and the steering mechanism and the accommodation, in the poop, was for twelve men.

Measurements: 375ft length oa
                            360 ft length bp
                              56 ft breadth
                              38 ft depth
                              28 ft 6 ins draught
Tonnages:         5,410 gross
                            6,600 deadweight

Yard No 1 was launched on 13 October 1942, the first launching of a concrete vessel in twenty-two years, after 166 days on the ways. She was finally delivered on 13 April 1943 after taking a total of 349 building days. This was the prototype and subsequent deliveries were worked down to less than a third of this time, mainly by added pre-assembly operations. The final delivery was made in May 1944. In the event, all these barges passed to the jurisdiction of the military authorities,

The first five barges were named CONCRETE NOS 1-5 (with the latter four being renamed - as below) and were operated by the US Navy. The remaining vessels, intended to be named as 'Concretes' were also operated by the US Navy and were completed as YO-type and YOG type fuel oil and gasoline barges, as follows:

                      Yard No 2                       became CONCRETE NO 2 then YO 144
                      Yard No 3                       became CONCRETE NO 3 then YOG 40
                      Yard No 4                       became CONCRETE NO 4 then YOG 41
                      Yard No 5                       became CONCRETE NO 5 then YOG 42
                      Yard No 8                       became YOG 53
                      Yard No 16, 19, 22        became YOG 82-84 (See how YOG82 looks today (Photo: John Campbell)
                      Yard No 6,7                    became YO  145-146
                      Yard No 9-13                  became YO  159-163
                      Yard No 14, 15, 17         became YO  182-187
                                     18.20.21

B5-BJ1 type

These vessels were double-deck covered lighters with a wooden housing.
Measurements: 265ft length oa
                            264ft length bp
                              48 ft breadth
                              17 ft 7ins depth
                              12 ft 9 in draught
Tonnages:          2,630 gross
                             1,632 deadweight

                        MC Hull Nos. 2214-2235                      Yard Nos. 23-44.

All the above lighters were taken over by the War Department, given US Army numbers BCL 3049-3070 and were used as floating warehouses and supply lighters.

B5-BJ2 type

These lighters were originally of the B5-BJ1 type, but were equipped with 130,000 cu ft of refrigerated space and were reclassified.

MC Hull Nos. 2236-2238                       Yard Nos. 45-47
Yard No. 45 HYDROGEN                      9.44
Yard No. 46 CALCIUM                        10.44
Yard No. 47 ANTIMONY                     11.44
The above three lighters were taken over by the War Department and given US Army numbers 3071-3073. They were used as refrigerated floating warehouses.

 B5-BJ3 type

These two lighters were originally of the B5-BJ1 type, but were completed as maintenance lighters for the US Army and reclassified. They were numbered FMS 1-2.
MC Hull Nos 2695-2696     Yard Nos 48-49       
Yard No. 48 CERIUM                      3.45
Yard No. 49 RADON                       5.45

Source: From America to United States, Part III by L. A. Sawyer and W. H. Mitchell (World Ship Society 1984)

 Read more here:
http://www.ww2pacific.com/concship.html 
http://www.concreteships.org/ships/barges/