What are the findings today?
Although water quality problems (notably wet weather discharges) still exist, the conditions on the Merrimack are greatly improved since the plant began operation. Bacterial counts are lower by orders of magnitude. The river now generally meets water quality standards for dissolved oxygen. Also, except during wet weather conditions, discharges of solids and grease have ceased.
Documented pollution levels:
1. “Coliform”: Coliform refers to a group of related bacteria that are often used as an indicator of the degree to which a waterbody is contaminated by pathogenic organisms. Although Massachusetts no longer has a standard for (total) coliform levels in rivers and streams, New Hampshire’s standard is “no sample greater than 406 counts per 100 milliliters”.
Coliform counts in the Merrimack River below Lawrence:
– 1963 Data: Average of all samples = 4,850,000 counts per 100 milliliters.
– 1994 Sample: Result = 190 counts per 100 milliliters.
2. “Dissolved Oxygen”: The dissolved oxygen level in a waterbody is one measure of its level of pollution by organic substances, such as contaminants in sewage. For a river body such as the Merrimack, the Massachusetts standard for dissolved oxygen level is “not less than 5.0 milligrams per liter”. Levels below the standard are evidence of significant contamination and could be toxic to fish.
Dissolved Oxygen Levels in River below Lawrence:
– 1963 Data: Average of all samples = 2.4 milligrams per liter (Some samples showed complete depletion (i.e. Ð 0) of dissolved oxygen.
– 1994 Sample: Result = 7.97 milligrams per liter