EM 1110-2-1100 (Part V)
31 Jul 2003
Figure V-4-7. Isopach map of a borrow area used at Ocean City, Maryland
Sediment composition can be determined by examining representative samples under a binocular
microscope. Samples should be prepared by thorough washing to remove fines and clean the surface
of the particles. If the material is not well sorted, it should be subdivided into sieve fractions for
analysis. A subdivision into the Wentworth classes (see Part III-1) for sand-sized and coarser
material is convenient for this purpose. The percentage of carbonate in the material can be estimated
by dissolving the carbonate fraction in multiple baths of hydrochloric acid with a subsequent sodium
hydroxide wash.
(g) Sediment size characteristics. Generally, suitable material will have grain sizes predominantly in the
fine to very coarse sand size range. The presence of very fine sand, silt, and clay in small amounts (generally
less that 10 percent) is acceptable, but sources having a substantial amount of fines should be avoided if other
more suitable sources are available. When using a borrow area with higher silt or clay content, a large
amount of material must be handled to obtain the usable portion, thereby increasing costs. Also, the creation
of turbidity during excavation and placement on the beach is environmentally undesirable. However, in the
future, as sand resources become more scarce, sand separation may prove to be economically justified
depending on the volume of material required and the relative silt and clay content of the borrow site. Borrow
material presently discounted because of a comparatively high percentage of fines may become economically
viable sand sources in the future.
One of the main considerations in selecting a borrow source is the similarity between the grain size
distributions of the borrow material and the native beach, i.e., the borrow material's compatibility
with the native material. To make this comparison, it is necessary to determine, for both native beach
and each potential borrow source, a composite grain size distribution representative of overall
textural properties. The method used to determine grain size characteristics for both the fill and
V-4-22
Beach Fill Design
Previous Page
