two low level pesticide detects one for atrazine at 0.13 ug/L and one
for 2,4-D at 1.8 ug/L. Neither of these pesticide levels approach
the ES levels, 3 ug/L and 70 ug/L, respectively, for these compounds
in ground water.


 In general, the analytical results indicated that medium-to-large
 sized, unlined yard waste composting facilities that allow organic
 wastes to decay anaerobically, generate leachates that have an impact
 on ground water quality.. This conclusion is not entirely surprising
 as many authors (Helfrich, 1992, Kovacic, et. al., 1992, and Cole,
 1994) have acknowledged that the potential for the-generation of an
 enriched leachate exists when organic materials decay anaerobically.
 The leachate quality results of this study were compared to the
 results of a study done by Helfrich (1992)(Table 5) on yard waste
 that was allowed to decay anaerobically under controlled conditions.
 The results show that the leachate from the study sites are well
 within the range of values found by Helfrich for anaerobic decay

 The most obvious ground water quality impact revealed during the
course of the study was the increase in nitrate levels in wells
downgradient of the composting facilities. The downgradient wells at
both sites had nitrate levels that were consistently higher than
nitrate levels at the upgradient wells. The nitrate levels in the
downgradient wells were, at times, 3 to 12 times higher than the
levels detected in the upgradient wells. The WDNR's enforcement
standard for ground water quality with respect to nitrates was
exceeded on four occasions at three separate downgradient wells
during the course of the study.

The leachate data can be used to verify that the yard waste compost
is contributing to the elevated nitrate levels in the ground water.
Nitrate levels in the leachate were generally low, between 0.023 and
37.2 mg/L with a mean value of 2.2 mg/L. However, the ammonia
concentrations in the leachate tended to be very high with levels as
high as 424 mg/L with a mean value of 74.2 mg/L. Conversely, the
ammonia concentrations in the ground water wells tended to be very
low, with values that never exceeded 3.5 mg/L.

Clearly what is happening is that ammonium (NH4) ions in the leachate
are interacting with the soil and the atmosphere to transform into
the nitrate and nitrite (N03 and N02) compounds found in the ground
water analyses. Hem (1992) detailed how reduced forms of nitrogen in
surface waters are commonly transformed into nitrate. Hem also cites
a study where waters high in ammonia were quickly oxidized in the
atmosphere to form nitrate and nitrite. Nitrogen in reduced or
organic forms can also be reduced by soil bacteria to form nitrate
compounds. The low levels of nitrate in the leachate could be caused
by the relatively low initial nitrogen content of yard waste
(Kovacic, et. al., 1992) or by the reduction of nitrates into nitrous
oxide or nitrogen gas under anaerobic conditions (Hem, 1992).