|
<br />
<br />Agti4tZ~ Standards Laboratory for Jli.t.J:llte for
<br />quality control evaluation.
<br />
<br />In addition to the inorganic parameters, all of
<br />the groundwater samples collected were analyzed
<br />for selected pesticides, The pesticide analysis was
<br />performed by the Colorado Department of
<br />Agriculture Standards Laboratory, A listing of
<br />pesticides was compiled for analysis based on those
<br />substances that have recently been, or are currently
<br />being utilized in the Arkansas Valley according to
<br />agricultural officials there. Budget restrictions
<br />would not allow testing for all pesticides used in the
<br />study area, To reduce the analysis cost, each
<br />pesticide was weighted according to its chemical
<br />properties of persistence and mobility in the
<br />environment, amount of active ingredient used per
<br />acre, and the amount of acreage within the study
<br />area that pesticide was used on, Pesticides were
<br />then selected according to their final score and the
<br />ability of the laboratory to detect their presence.
<br />
<br />The results from this sampling program have
<br />been entered into the C.OPHE Grollnrlwater Quality
<br />Data System, a database located at CDPHE. A
<br />detailed reoort describing the area sampled, the
<br />(Protocol fui- sampling and analysis, and the results
<br />of the analvsis was provided to the Commissioner
<br />of Agriculture in early 1997.
<br />
<br />~
<br />
<br />
<br />.Re$'ult$~f~~esticideAn~I~
<br />, ':F"i".t ^ , ,
<br />
<br />, 'Pesticicl~: .
<br />
<br />Use
<br />
<br />Herbicidlil'
<br />Herbicide'
<br />Herbicide
<br />
<br />Atrazine' .
<br />MetolacHlbl"
<br />2;4-D '
<br />
<br />Analysis of laboratory results for the Arkansas
<br />Valley indicates that ground water in parts of the
<br />study area has been impacted by various
<br />agricultural chemicals. The maior inorganic
<br />contaminant of concern is nitrate. Nineteen of the
<br />one hundred thirty nine wells sampled (1~)
<br />showed nitrate levels in excess of the EP A standard
<br />-
<br />for drinking water (10 mg/L). The drinking water
<br />standard is used as a benchmark for nitrate levels in
<br />all wells regardless of use because the alluvial
<br />aquifer is a significant source of drinking water in
<br />the valley. Twelve of the one hundred thirty nine
<br />samples ( 9%) showed oositive for the herbicide
<br />Atrazine. One sample detected the herbicide
<br />Metolachlor and one sample detected the herbicide
<br />2,4-D. AILPesticide detections where well below
<br />the drinking water standard.
<br />"
<br />
<br />A confirmation sampling was performed on
<br />those wells that had a nitrate level above 10 mg/L,
<br />or a pesticide detection in 1994. The confirmation
<br />sampling tested 32 wells and found little change
<br />from 1994, indicating a high level of confidence in
<br />the initial work. Nitrate levels were statistically
<br />unchanged and the only pesticide detected was
<br />Atrazine. One well did contain Atrazine at a level
<br />above the standard of 3.0 ug/L.
<br />
<br />""'ot;i;~:>~"; 0
<br />
<br />~'o',o /~
<br />
<br />,(j):O$
<br />'OM
<br />'0' c'O"2^"
<br />0, ,.,. _' '0:,-',
<br />, " .". ,.
<br />,m, ,0 '. '., '
<br />
<br />'>1>2 '..
<br />,.'m;,i'.','
<br />'1",'
<br />-'-,-,'
<br />
<br />~m()unts aregivenih'Mi~rograms peiHter.orp~~^~'r/ilet::billion\", ..
<br />, .', -', ,,'_,,-, '_ :..._ -, \_ c~'_,' j<J':'<'",_ _ _ ,,_ ~ _"':-"-"^"<,^ _, '//e"o,,;Lx^' ;,:,,,-:,:-,'0_',,_,>:,_ ___'__',__':_"_,<,
<br />DLi-MinimUmc\ln~~fI~.~tion that canOedi'll' -'\ ":ffjell3,bOratorY
<br />Met~The maximum:'iimountallowed'inarfhkln Sr" \'
<br />, ", ., .: " :,J~~~:~L": -, " "- -, -":'''':::<' .;.<.H
<br />
<br />, :"'-,,.,
<br />,J,' ):5.:~~::t}~:Y;-
<br />
<br />
<br />Page 3
<br />
<br />l .
<br />),--"",'--.-_;~~'(:J!_:,~" .
<br />'., ",-.' ,-,,t.,,,-lnk:, . _ -"'<<,,, ,
<br />~_".:,.<J,~.l_.',-'tfi-"):t>' "'_"~."'_
<br />
<br />-"";:0"_,0
<br />
<br />
|