Number of Sample Locations, Sampling Procedure, and Testing

Custom Search

Back

Up
7_BEACON Tech Report (FINAL)

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.

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.

4-7

Moffatt & Nichol Engineers