The performance of silt fences has not been well defined. Laboratory studies using carefully

controlled conditions have shown trapping efficiencies in the range of 40 to 100 percent, depending

on the type of fabric, overflow rate, and detention time (Barrett et al. 1995; Wyant 1980;

Wishowski et al. 1998). Field studies have been limited and quite inadequate; however, the results

show that field-trapping efficiencies are very low. In fact, Barrett et al. (1995) obtained a value of

zero percent trapping averaged over several samples with a standard error of 26 percent. . . .

Silt fences are effective at removing large particle sediment, primarily aggregates, sands, and

larger silts. Sediment is removed through impounding of water to slow velocity. It is argued that

the silt fence will not contribute to a reduction in small particle sediment and is not effective

against other pollutants (WYDEQ 1999). EPA (1993) reports the following effectiveness ranges

for silt fences constructed of filter fabric: average TSS removal of 70 percent, sand removal of

80 to 90 percent, silt-loam removal of 50 to 80 percent, and silt-clay-loam removal of 0 to 20

percent. However, EPA numbers from the Nationwide Urban Runoff Program should not be

considered to apply to every location. The actual trapping will vary widely for a given design

because of differences in hydrologic regimes and soil types.56

Sediment basins are also commonly used on construction sites in Virginia and, generally,

the discharges from these installations enter surface waters directly. Therefore, the

efficiency of these measures are particularly important for water quality. The EPA

Development Document notes that “[t]he effectiveness of a sediment basin depends

primarily on the sediment particle size and the ratio of basin surface area to inflow rate

(Smolen et al. 1988; Haan et al. 1994).” The document cites studies conducted in the

coastal plan and piedmont regions of Maryland and cautions that these data should not

be used for a more generalized assessment.7

2. Virginia officials have ignored the abundant evidence available to them which proves

that the general permit’s technology-based limits have not and cannot uphold water

quality standards, under many circumstances and at locations across Virginia and failed

in their duty to ensure that activities will not be covered under the general permit

unless water quality standards are met.

Thousands of miles of streams in Virginia are impaired such that designated and/or

existing uses are negatively affected. Some of these have been designated “impaired” and

included on the list the state is required to prepare under § 303(d) of the Clean Water Act.

For each of these “listed” waters, the state or EPA must prepare a Total Maximum Daily

Load (“TMDL”) and limit pollutants of concern in accordance with that TMDL.

5 U.S. EPA, Development Document for Final Effluent Guideline and Standards for the Construction &

Development Category, November 2009, pp. 7-49, 7-50.

6 I ask that you incorporate the entire development document listed in footnote 5 into the record for this

regulatory action by-reference.

7 Ibid, p. 7-63.

Many other waters in the state have not been designated “impaired” but have existing

pollution problems that violate numeric and/or narrative water quality criteria. The

DCR fact sheet for this general permit includes no mention of these water bodies and the

permit provides no protection for them to prevent further degradation from construction

stormwater discharges covered under this permit. It must be noted that permitting

officials are obligated to consider all data available to them when analyzing the potential

impacts from discharges to be covered by an NPDES permit. The absence of an official

designation of “impairment” does not relieve Virginia officials of this duty.

Also, waterbodies that currently are of high quality must receive protection under

antidegradation provisions in both federal and state law. Again, the fact sheet provides no

analysis that in any way gives assurance that general permit can prevent lowering of

water quality in those waters. The substantial quantities of pollutants that are known to

be discharged from construction sites (as demonstrated by the reports of quite limited

treatment capabilities of BMPs in documents cited above) must increase pollutant levels

in many of the streams in Virginia. Those that are currently not polluted by measurable

concentrations of phosphorous, nitrogen, or sediments will inevitably be degraded and

experience violations of the antidegradation policy due to construction stormwater

discharges. We have witnessed and documented such occurrences in the past on

numerous occasions. Even a sediment detention basin or retention pond that is operating

in the optimal range will discharge amounts of these pollutants well in excess of the

background amounts in many unimpaired waters.

Nutrients

Shenandoah Riverkeeper has collected an extensive record to show water quality

degradation in the mainstem Shenandoah River, as well as the North and South Forks of

the River. I am attaching a document with this letter entitled Shenandoah Riverkeeper and

Earthjustice Comments on Virginia’s Integrated Water Quality Report and list of impaired waters under

CWA § 303(d) and ask that it be incorporated into the record also. That document

summarizes the evidence Riverkeeper has compiled in regard to nutrient impairments. It

is important to note that phosphorous often becomes bound to soil particles and is washed

into water bodies as erosion occurs during land-disturbing activities.8

A number of metals may be present on the land and can be carried into waterbodies

through stormwater runoff and eroded soils. Both DCR and Virginia Tech studies have

shown that lands large portions of land in the Valley of Virginia have had large quantities

of arsenic and lead applied to orchards and crop lands, through the use of pesticides

throughout the first half of the twentieth century.

8Numerous researchers have documented that phosphorus losses in runoff are highly correlated to soil

phosphorus concentrations (Sims et al., 2002; Maguire and Sims, 2001; Pote et al., 1996).

A number of BMPs on construction sites employ detention of runoff water and settling to

remove pollutants. In many cases these water will warm substantially, especially in

summer and, when discharged to surface waters, will likely result in violations of instream

temperature criteria violations.

3. The lack of adequate application requirements, together with the flawed process

through which coverage under the general permit may be granted, constitutes an illegal

system of self-regulation for operators of land-disturbing activities who seek coverage

under the general permit.

The opportunity for citizens to help shape water quality limitations and permit conditions

and to involved in enforcement of those permits is a cornerstone of the Clean Water Act.

Public notice and opportunity to comment on regulatory proposals and permits are

mechanisms that were highly valued by the Act’s drafters and are meant to be not only

allowed but encouraged by EPA and other permitting authorities. The failure of the

DCR and the Soil and Water Conservation to provide for full public participation in the

I ask that the following documents be incorporated by-reference into the record for this

rulemaking:

Virginia’s General VPDES Permit For Discharges Of Storm Water Associated With

Industrial Activity (9 VAC 25-151)  (the Virginia DEQ amended this general permit in 2009 to incorporate a public notice and comment procedure into the permit, to allow citizens to help shape the permit

limitations contained in SWPPPs for industrial sites.)

Centner, Terence J., Challenging NPDES Permits Granted Without Public Participation, Boston

College Environmental Affairs Law Review, Volume 38, Issue 1, 4/1/2011.