72 BULLETIN 949, TJ. S. DEPARTMENT OF AGRICULTURE. 



57. SAMPLING SEMIGRAVEL, TOP SOIL, AND SAND-CLAY. 



Samples of materials of this class shall be of two kinds: Class I, samples of the raw 

 material taken from the natural deposit; Class II, samples of the loose material after 

 being mixed in place on the roadbed and before consolidation. 



Class I samples shall be used simply as preliminary evidence of the suitability of the 

 aggregate, subject to admixture of one or more ingredients to adjust the composition 

 to the limits set forth in the specifications. 



The final acceptance of the material as satisfying the specifications shall be based 

 ^.n Class II samples. 



Standard containers. — (1) A three-compartment box of pasteboard, wood, or metal, 

 outside dimensions 5 by 10 by 10 inches; or (2) close woven bags or sacks of material 

 which do not allow sifting out of fine particles, dimensions 6 inches wide by 12 inches 

 long. 



Labeling. — Each compartment in the box container must contain a label showing 

 at what depth the contents were taken. The whole sample shall be accompanied by 

 a card, securely attached thereto, stating date, by whom taken, by whom submitted, 

 source of supply, exact location where sample was taken, position within the deposit 

 where taken, owner, quantity available, amount and character of stripping, if any, 

 whether material from same source has been previously used, where, and with what 

 results, haul to nearest point on road, average haul to job, character of haul, initial 

 cost of material. 



When bag containers are used, one complete sample shall comprise 3 bags, each bag 

 labeled as to depth from which the material is taken. 



Each bag, or, if preferred, a larger receptacle containing the three bags, is to be 

 labeled with the information detailed above. 



How to take Class I samples. — For each 1 acre or less of area two samples must be 

 taken, one a local sample and the other a composite sample. 



The local sample is to be taken near the center of the area and is intended to represent 

 the vertical average of the material at that point. It shall be taken in three layers, 

 each layer inches thick, according to the method described as follows: 



The material is to be loosened over a 3 by 3 foot area to the specified depth, usually 

 4 inches. The loose material is to be intermixed with a shovel and the sample for 

 one compartment of the box container or one of the bags is to be taken therefrom. 



The remaining loose material is to be shoveled out and discarded. The second 

 layer is to be loosened to equal depth, usually 4 inches, to be intermixed as before, 

 and a second compartment or bag is to be filled. The same procedure shall apply 

 to the third layer and the filling of the third compartment or bag. 



In exceptionally thick deposits the depth of each layer or the number of layers 

 may be increased to cover the entire thickness of the deposit. 



The composite sample is to be taken as follows: Roughly divide the area to be rep- 

 resented by the sample into squares not exceeding 50 f eetin size. At the corners of all 



squares loosen a 3 by 3 foot area to a depth of 13 inches. Thoroughly mix the loose 



material. Carry an equal amount of the material from each such point to a central 

 point and intimately mix the various samples. Not less than 200 pounds of material 

 must be so mixed. From the center of the pile of mixed material fill a container and 

 label for shipment. 



Where the material occurs as a substratum sink no less than four 3 by 3 foot pits per 

 acre or smaller area to intersect the material. Remove the covering, and sample the 

 exposed bed as for a local sample described above. 



How to take Class II samples. — These are the mostimportant samples and should be 

 taken by the engineer or competent inspector while work is in progress. 



13 A depth of 8 inches is suggested. 



