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Number of Wells that Tested Positive for Total Coliform Bacteria – A total of 7,035 (13%) of 51,028 wells tested were positive for total coliform bacteria. This was not considered a “failure”, but these wells were then required to do follow-up testing for fecal coliform or E. coli. The NJDEP believes that a significant percentage of wells testing positive for total coliform are not actually contaminated with fecal waste. Some coliform of non-fecal origin may be present as buildup in the plumbing system, for example. Number of Wells that Tested Positive for Fecal Coliform or E. coli – A total of 1136 ( 2 . 2 % ) o f t h e 5 1 , 0 2 8 w e l l s t h a t w e r e s a m p l e d w e r e p o s i t i v e f o r e i t h e r f e c a l c o l i f o r m or E. coli in at least one of the samples collected at the well. presented by county in Appendix E. These data are

Geographic Distribution – The percentage of wells with fecal coliform or E. coli in the combined counties above Burlington and Monmouth (“northern”) was 3.5%. In the remaining (“southern”) counties, the percentage was 1.0% (see Figure 3 above). The NJDEP believes the northern/southern difference is real and not an artifact of the use of different labs or different methods in these two regions. Both laboratory and method biases exist but do not account for the observed difference between the northern and southern parts of the state. The difference is most likely due to the different geology in these regions. The geology in the north is characterized by areas with limestone subject to solution cavities (called karst), fractured bedrock and gravel/cobble water-bearing zones. The southern part of the state is comprised

mainly of the coastal plain (alternating layers geology appears to protect ground water from

of sand and clay). fecal contamination

Coastal plain better than the

other geological areas of the state. Comments – The percentage of wells coliform or E. coli after the two years

testing positive for total coliform of PWTA testing, when the data

and fecal were first

analyzed, was 13% and 2.1%, respectively (compared to between September 2002 – April 2007, respectively).

13% and 2.2% failure rate Thus, the percentages of

wells testing positive are consistent following the

wells.

In

the

absence

of

any

significant

change

testing in the

of an extent

additional 24,964 of fecal pollution

impact, the percentages found in this any significant extent in the future.

analysis

would

not

be

expected

to

change

to

For the bacteriological analysis, the data are based on a single sample in 91% of the cases.7 Thus, the 2.2% fecal coliform/E. coli -positive figure should be considered a

lower limit of the true extent of microbes are randomly distributed

fecal contamination in New in ground water and because

Jersey. Because fecal contamination

can often be low or intermittent, a single sample can miss the Alternately, fecal contamination may be present in some samples in

contamination. the absence of

coliform bacteria8. A reasonable statewide is perhaps an additional

estimate of the true one or two percent.

extent

of

fecal

contamination

7 Test results are valid for 6 months. For homes that sold more than once during this four and half year period, or did not sell within a 6-month period, the well was tested more than once. The 51,035 wells included 4,431 with multiple t e s t r e s u l t s ( 9 3 . 3 % o f t h o s e w e r e t e s t e d t w i c e ; 6 . 1 % w e r e t e s t e d 3 t i m e s ; a n d 0 . 5 % w e r e t e s t e d m o r e t h a n 3 t i m e s . ) 8 Atherholt, T. et al. October 2003. Evaluation of Indicators of Fecal Contamination in Ground Water. American Water Works Association. 95 (10): 119. Journal

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