Lake Bacteria

State Standards for bacteria

Recreational use:

  • 200 colonies of fecal coliform bacteria /100ml for primary contact recreation
  • 1000 colonies of fecal coliform bacteria /100ml for secondary contact recreation

Swimming beaches:

  • geometric mean of 33 enterococcus bacteria or 126 E.coli bacteria per 100 ml of water (fresh water)
  • geometric mean standard of 35 enterococcus bacteria per 100 ml of water for five samples over 30 days and an instantaneous (single sample) standard of 104 enterococcus bacteria per 100 ml of water (salt water).

Lake Sampling

**For the Mass. Department of Environmental Protection-approved SOP, get the pdf file here**

Equipment

  • Sterile pre-labeled High Density Polyethylene (HDPE) bottle, 250 ml
  • Pair of latex gloves
  • Hip boots or chest waders (near-shore sampling only)
  • Rinse water and towel
  • Field data sheet and pencils
  • Cooler
  • Cubed ice
  • Frozen koolit
  • Zip-loc bag (1-gallon size)
  • 1 personal flotation device per person (boat sampling only)

Sampling Protocol

Wash hands with rinse water and dry with towel before starting sample run. If you sample in an area that may have high fecal levels, rinse hands before handling the next sample bottle.

Be careful not to touch your hands to yourself before you have cleaned them in order to avoid coming into contact with pathogens. If you are sampling from waters known to be contaminated with sewage, wear latex gloves to protect yourself.

Near shore sampling: Carefully wade into the lake to a depth of about 2 feet and avoid stirring up bottom sediment. Stop and wait for pre-disturbance (from wading in) conditions to return before taking sample. If a dock is present, it is acceptable to sample from there, provided the water depth is at least two feet.

Boat sampling: Be sure to sample where the lake is more than 1 foot deep, and drop anchor on the side opposite to where you will collect sample. Wait for any disturbance of the bottom to settle and dissipate.

Place upright, capped sterile sample bottle under the surface of the water about 6 inches. Do not rinse the bottle. Slowly uncap and let it fill to capacity under the water. With hands away from the bottle opening, bring the bottle up and out of the water, pour off a little water to leave some air space (approximately 1/2 inch) in the bottle. Cap the bottle and tighten.

Transport

See river protocol.