storms (4 inches per hour or more) shortly after application. Environmental contamination risk is highest
in this situation, especially on cultivated cropland before incorporation because of the greater likelihood
that severe thunderstorms will produce significant runoff that contains concentrated quantities of nutrients,
organic matter, and microorganisms derived from biosolids and that this runoff will enter surface waters.
Scheduling deliveries to take into account expected weather is the best way to minimize this risk.
Pollutant transport from surface applications of biosolids on sandy soils above shallow groundwater will
result in greater impact on the quality of local groundwater than similar applications on heavier textured
soils where the water table is lower. Similar results can be expected from commercial fertilizer applications
under the same circumstances. The rainfall simulation on Smith’s farm showed that lower or similar
transport rates for total suspended solids, N and P, can occur from applications of biosolids compared to
commercial fertilizer (Evanylo and Ross, 1997). The rainfall simulation also indicated that heavy metals
and pathogens in runoff from the biosolids-amended crop and pasture plots were no higher than those
from the commercially fertilized plots.
The permitting process requires avoiding steep slopes and identifying and protecting sensitive areas such
as water bodies and wetlands, which could be negatively affected by direct loading of biosolids. Biosolids
companies must meet all permit requirements, including setback regulations, or they can be found in
violation of their permits and have them revoked. The Virginia Department of Health, Biosolids Use
Regulations stipulate specific setbacks for eight distinct categories: occupied dwellings, water supply
wells or springs, property lines, perennial streams and other surface water bodies, intermittent streams
and drainage ditches, improved roadways, rock outcrops and sinkholes, and agricultural drainage ditches
with slopes equal to or less than 2 percent. The setback rules apply to surface applied, incorporated, and
winter applied biosolids. For example, the required setback from sensitive areas ranges from 10 feet
along improved roadways to 200 feet from occupied dwellings (Va. Dept. of Health). These buffers
represent a practical means to help assure environmental protection.
Except for conservation tillage, conservation practices are very compatible with biosolids applications.
Grassed waterways act as both vegetative buffers and conveyance courses to control runoff and non-
point source pollution. Buffer strips, required by the Chesapeake Bay Preservation Act, increase infiltration
and diminish surface runoff. Field borders function in a similar manner to buffer strips. These conservation
practices take up nutrients in runoff and trap sediments and suspended solids. Forested riparian buffers
are present in many areas of the Coastal Plains and Piedmont of Virginia. Riparian buffers also function
like buffer strips to filter out non-point source pollution. Thus, existing conditions at many agricultural
sites are favorable for biosolids applications to take place without significant environmental degradation.
Surface spreading of biosolids by suppliers without incorporation is the most common application practice
in Virginia. Incorporation is used to reduce odors, nitrogen volatilization (nitrogen losses to the atmosphere),
nonpoint source pollution, and soil compaction resulting from the application. Surface spreading is faster
and less expensive than incorporating or liquid injection and avoids a potential conflict with federal farm
program participation, but surface spreading may result in violating Department of Health requirements.
Direct injection or incorporation within 48 hours is required by the Virginia Department of Health if a site
has less than 60 percent crop residue or living cover or if it is applied to soils subject to frequent flooding.
If the remaining crop residues after biosolids are disked in are below the USDA conservation plan
required coverage of 30 percent ground cover after planting, the farmer could lose program benefits for
noncompliance. To avoid possible conflicts, farmers participating in USDA programs requiring conservation
plans should review their plans with their local USDA/Natural Resources Conservation Service (NRCS)
office.
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