Enterococcus Level

Enterococcus is a bacteria that can cause illness in humans and animals.  Water can be tested for enterococcus and test results are typically available about 24 hours after samples are collected.  Results are expressed as Most Probable Number (mpn) of enterococcus per 100 ml of water.

This website provides mpn results and color indicators that are easier to understand:

• PASS - A water site is marked green and PASS when the geometric mean of 5+ samples is equal or below 100 mpn of enterococcus per 100 ml of water.  If only a single sample is available, PASS means equal or below 200 mpn of enterococcus per 100 ml of water.
• FAIL - A water site is marked red and FAIL when the geometric mean of 5+ samples is above 100 mpn of enterococcus per 100 ml of water.  If only a single sample is available, FAIL means above 200 mpn of enterococcus per 100 ml of water.
• UNKNOWN - A water site is marked grey when there are no results or there is no available information.

NOTE: It is important to note the date the enterococcus level was collected.  Enterococcus levels can change significantly from one day to the next as environmental conditions change.  To avoid misleading people, when results are from more than 8 days ago, PASS and FAIL indicators will display in grey as OLD PASS and OLD FAIL.