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describes the existing sediment grain size conditions at each site. Also, Appendix A
contains the results of the sediment grain size analysis for each of the six beach fill sites.
2.
The time of year when fines in beach fill are mobilized by waves and suspended in the
water column should not differ greatly from when material is introduced to the water
column by natural phenomena (i.e., all-winter placement or two-thirds of sand volume
placed during the Fall-Winter season, between September 15 and March 15).
Informal USACE guidelines titled "Requirements for Sampling, Testing and Data Analysis of
Dredged Material" were reviewed to address these sediment issues (1989). This report expands
upon the USACE procedure by considering other properties (color, compactability, etc.) of
upland borrow material, which are not formally considered by the USACE in published
guidelines.
Number of Sample Locations, Sampling Procedure, and Testing
Sediments will be sampled at each potential sand source location. The gradation of this
material will be compared to the gradation of the existing beach sites. This section
recommends the number of samples to be collected, collection sites, sampling procedure,
testing, and data analysis and display to evaluate sediment size compatibility for the
Program.
In the absence of formal guidelines, the USACE (1989) specifies the number of locations
to be sampled at each borrow site, N, as
N = A1/2 50
(1)
in which A is the plan area of the borrow site in square yards (about 1.5 sample stations
per acre). The USACE notes that in no case will less than three sampling locations be
acceptable. The USACE (1989) does not specify the procedure for taking samples of
potential beach fill material on land. Samples from a proposed dredge area are taken to
the proposed depth of dredging plus 2 feet. For the purposes of sampling potential sand
source sites on land, the sampling program should be consistent with the USACE
Equation (1) sampling density, and one sample at each location be obtained below the soil
horizon (at either mid-depth or at the bottom of the excavation). All samples will be
sieved in accordance with American Society for Testing and Materials (ASTM) D 422-63
(Test Method of Particle-Size Analysis of Soils, ASTM 1999).
This procedure can be used as an initial guideline, but should be reconsidered for specific
conditions, with additional samples taken as necessary. Additional samples could be
required based on variable stratigraphy. However, most potential sand sources are flood
control debris basins, which are located in previously undeveloped areas so the USACE
guidelines may be appropriate.
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