Geosynthetics April/May 2021 - 31

and 70% filtration efficiency and high
flow rate. It should be noted that most
of the products from this category were
open-weave geotextiles, which may be
appropriate for use as a prefilter prior to
runoff reaching a point of concentration
before being released off-site or as a filtration component in areas where trash
migration is an issue.
ASTM D7351 test data
Figure 4 presents results of D7351 testing
of a wide range of SRD types commonly
used in linear, toe-of-slope applications.
SRDs tested include both woven and nonwoven geotextile-based silt fence, along
with various proprietary composite and
woven fences and socks/wattles.
Discussion of D7351 data
ASTM D7351 was used for the evaluation of 12 unique two-dimensional silt
fence SRD products and 10 unique threedimensional sock/wattle SRD products
in this research. All the products were
subjected to the theoretical 30-minute
peak discharge of a design storm event,
as prescribed in the standard calculated
using the MUSLE. The resulting influent
sediment concentration is prescribed at
approximately 6%, and the soil type used
in this research was loam with a PI ≤ 8.
The data displays a clear delineation in
performance between the two-dimensional
and three-dimensional SRD products.
Two-dimensional SRD products tested
via ASTM D7351 provide consistently
high sediment retention efficiency, with all
tested product providing no less than 82%
sediment retention efficiency. However,
performance of the two-dimensional
SRD category, in terms or water retention
efficiency, ranges greatly, from 7% water
retention effectiveness to 98% water retention effectiveness over the course of the
design storm. This relationship is most
likely a result of the material characteristics
of the tested product, specifically, weave

geometry. In the data, the products with
lower water retention effectiveness are all
composed of plastic monofilament fibers,
while the products with higher water
retention effectiveness are composed of slit
film fibers. As discussed earlier, the differences in manufacturing of these filtration
component fabrics leads to a marked difference in flow rate, and thus water retention effectiveness. Encouragingly, these
results provide reasonable agreement with
the performance of product categories
tested in the ASTM D5141 testing program
described previously.
Separately, the data displays relatively
consistent performance from the threedimensional SRDs tested in this program.
All three-dimensional products provided
high sediment retention efficiency, with
performance ranging from 88% to 98%
efficiency. However, as a product category, and as opposed to two-dimensional
SRDs, three-dimensional SRDs have a
consistently lower water retention effectiveness percentage (Figure 5 on page 32).
This is a result of the vertical profile, or
effective height, of the three-dimensional

FIGURE 4 ASTM D7351 performance
testing results

www.GeosyntheticsMagazine.com

http://www.GeosyntheticsMagazine.com

Geosynthetics April/May 2021

Table of Contents for the Digital Edition of Geosynthetics April/May 2021