Effects of Rainfall on E. coli Concentrations at Door County, Wisconsin Beaches

Table 8

E. coli concentrations (*MPN/100 mL) from beach water collected at time intervals following the triggering of a rain event at Sunset Park beach. While there was a significant difference between the mean E. coli concentration during a rain event and the seasonal mean E. coli concentrations for this beach using ANOVA (Table 1), Scheffe matrix analysis showed no significant difference between E. coli concentrations at each sampling times after a rain event and the seasonal E. coli mean.. If rainfall was sufficient to trigger multiple rain event notifications on one day, then multiple events were sampled.

Date of Rain Event	Outfall Pipe 1–3 Hours	1–4 hours After	8 hours After	12 hours After	24 hours After
	After Rain Event	Rain Event	Rain Event	Rain Event	Rain Event
6/4/07	n/a	739.8	238.2	198.9	44.3
6/17/07	n/a	482.7	111.2	68.9	13.1
6/18/07	n/a	39.5	73.8	46.8	18.5
6/18/07	n/a	52.7	46.4	159.7	29.5
6/20/07	n/a	45.6	36.9	187.2	21.3
7/10/07	n/a	594.8	39.3	43.5	4.1
7/11/07	n/a	48.8	13.5	18.7	7.4
7/12/07	n/a	504.1	17.1	13.2	7.4
7/26/07	n/a	182.6	178.5	172.5	42.5
8/28/07	n/a	93.7	45.9	65	25.3

∗Most probable number.