Blame Canada geese for recent sliming of Chestnut Hill Reservoir

The MWRA is looking at steps to prevent a recurrence of the recent blue-green-algae infestation in the Chestnut Hill Reservoir that include treating the water with alum, which basically prevents the organisms from obtaining the phosphorus they need, and figuring out what to do about Canada geese, which that poop out the stuff like nobody's business.

In a message posted to reservoir and Allston/Brighton forums, MWRA Director Fred Laskey said an outbreak that popped up last month - the second this year - seems to have largely subsided on its own and that water testing showed no trace of the dog-killing, people-sickening toxins normally associated with the ancient life form.

Laskey said his experts are pretty sure the phosphorus comes out of the rear end of geese, because the reservoir - now used as a water source only in emergency situations has virtually no watershed, "with no storm drains or road run-off getting into the water:"

On any given day, 50 to 100 geese can be seen in and around the reservoir. A simple walking inspection along the reservoir perimeter path shows large amounts of goose droppings, which are known to be high in phosphorus and other nutrients. I should also point out that there is no other major source of nutrients getting into the reservoir. The reservoir has a very small tributary area with no storm drains or road run-off getting into the water. We have discussed control options with our partners at DCR: this is still developing. One short-term action is the installation of signs about the geese issues and warnings against feeding them. You will likely see these go up soon.