Environmental Safeguards Forest sites are managed in accordance with state biosolids management guidelines, including careful site selection and layout, correct nitrogen application rates, and monitoring of soils and streams. These best management practices were based on years of research and operational experience.
 Monitoring water quality at a stream near an application site.
Stream monitoring Streams and wetlands are protected by setbacks, or buffer areas, that are not fertilized. Depending on site-specific conditions, setbacks range in size, from the minimum of 33 feet required by federal and state rules, up to 200 feet. Water quality of streams near biosolids application sites is monitored to ensure that surface waters are protected. Wherever possible, water upstream of the units is collected for comparison. Storm events are also sampled to verify that the site has adequate buffers. Since 1986, water samples from forest streams near our application areas have been analyzed for ammonia nitrogen, nitrate-nitrogen, fecal coliform and enterococcus. Streams are also sampled during major storms to verify that buffers prevent runoff. Nearly 20 years of monitoring forest streams near our sites has shown no changes to surface water quality from biosolids. 
Effects on wildlife Since the 1970's, UW researchers and others have conducted studies on the effects of biosolids applications on forest wildlife. From soil microbes to larger animals, biosolids benefit the forest ecosystem. Biosolids create healthier soil by providing food for soil microbes and plants. Because of lusher vegetation growth, herbivores such as deer and small mammals have a more abundant and nutritious food supply, more protective cover, and produce more offspring. Studies at the UW's C.L. Pack Experimental Forest (external link) near Eatonville, and at the Snoqualmie Forest found no negative impacts on wildlife caused by biosolids application activities. In fact, studies have shown that deer and elk prefer biosolids fertilized areas because the forage there is more nutritious than that of non-fertilized areas. In addition, does foraging in biosolids fertilized areas have more fawns than those in non-fertilized areas. Studies conducted on small mammals such as shrews and mice, and on reptile and bird species at in northwest forests showed no harmful effects from biosolids. 
A haul truck unloading biosolids at a new application site.
Other concerns Prescribing the right amount of nitrogen is the most important technical element of these projects. However, people often ask about the potential for long-term impacts from metals in biosolids. King County's biosolids have very low levels of metals - well below the EPA and state standards for use on food crops. In addition, metals in soils and biosolids are environmentally stable, bound so tightly to biosolids that they do not leach or move through the soil. Long term local research has confirmed that metals pose no threat to groundwater, surface water or animals.
Public involvement Neighbors and other interested parties are encouraged to visit these projects. Your comments are always welcome. For more information or to arrange a tour, please contact the biosolids management program. Other beneficial uses of King County biosolids: |
