Environmental Challenges for the Lower Merrimack River
Bacterial Challenges
Reducing high levels of bacteria in the Lower Merrimack River has been a top priority for the Lower Merrimack River.
Elevated bacteria levels are primarily caused by the following sources:
- Illicit sewage discharges to storm drain systems
Illicit discharges are generally any discharge from a storm drain system that is not composed entirely of stormwater. Illicit discharges are a problem because, unlike wastewater which flows to a wastewater treatment plant, stormwater generally flows to waterways without any treatment. Illicit discharges often include sewage, bacteria, viruses, phosphorus and nitrogen (nutrients), surfactants, and various toxic pollutants.
Illicit discharges are generally any discharge from a storm drain system that is not composed entirely of stormwater. Illicit discharges are a problem because, unlike wastewater which flows to a wastewater treatment plant, stormwater generally flows to waterways without any treatment. Illicit discharges often include sewage, bacteria, viruses, phosphorus and nitrogen (nutrients), surfactants, and various toxic pollutants.
- Combined Sewer Overflows (CSO)
CSOs occur when wastewater containing untreated human waste, industrial waste and other debris is carried through the stormwater pipes and discharged into the River. Many sewer systems originally were designed to carry sewage and stormwater in the same pipe to a sewage treatment plant. After heavy rainfall or snowmelt, however, the wastewater volume can be more than the sewer system or treatment plant can handle. For this reason, combined sewer systems were designed to have safety valves that allow overflow after rain events, which results in wastewater being discharged directly into the river.
Wastewater treatment plants in Manchester and Nashua in New Hampshire and Lowell, Massachusetts impact water quality when heavy rains result in wastewater being discharged directly into the river through combined sewer overflows. Each of the communities with combined systems discharging to the Merrimack are making progress toward controlling overflows.
Information on Combined Sewer Overflows (CSOs)
To learn more about the status of EPA's enforcement actions aimed at reducing harmful overflows to rivers in New England CSO consent decrees (PDF) (3 pp, 68 K, About PDF)
- Uncontrolled urban stormwater runoff that contains pet and animal waste
Stormwater runoff occurs when precipitation from rain or snowmelt flows over the ground. Impervious surfaces like driveways, sidewalks, and streets prevent stormwater runoff from naturally soaking into the ground. Stormwater can pick up sediments, oil, nutrients like phosphorus and nitrogen that can cause algae, debris, chemicals, dirt, and other pollutants, which flow into a storm sewer system or directly to a lake, stream, river, wetland, or coastal water. Anything that enters a storm sewer system is discharged untreated into the waterbodies we use for swimming, fishing and sometimes drinking water. Pet waste can be a major source of bacteria and excess nutrients in local waters.
For more information on Stormwater Challenges.
Nutrient Challenges
Nutrients, primarily phosphorus, are a chief culprit for dramatic algae blooms that plague the River with blue-green algae during the summer months.
These "blue green" algae blooms, are a form of bacteria known as Cyanobacteria, whose cells may release a toxin when they die. Exposure to the toxin can cause skin rashes and irritate the nose, eyes or throat, and if ingested can lead to serious liver and nervous system damage. Other harmful effects of the algae include reduced water clarity, nuisance scum, and reduced oxygen in the water which is necessary for a healthy fish habitat.
For more information on Nutrient Challenges.
Stormwater Challenges
Stormwater runoff is generated from rain and snowmelt that flow over land or impervious surfaces, such as paved streets, parking lots and building rooftops, and does not soak into the ground. The runoff picks up pollutants like trash, chemicals, oils, and dirt/sediment that can harm our rivers, streams, lakes, and coastal waters.
Water that is discharged from municipal separate storm sewer system are regulated under the NPDES Storm Water Program Municipal Separate Sanitary Stormwater (MS4) Permit. There are also opportunities to use green infrastructure approaches, which use natural processes to improve water quality by managing water at its source.
Information about green infrastructure can be found:
- General information about Green Infrastructure
- Green Infrastructure for Municipalities (PDF) (36 pp, 3.5 MB, About PDF)
- Green Infrastructure Wizard - GIWIZ
Information about Massachusetts MS4 permit
- Factsheet about Massachusetts Stormwater Permit (PDF) (2 pp, 322 K, About PDF)
- Map of regulated communities in Massachusetts
Litter
Litter and trash in water ways is a significant concern in some sections of the Merrimack River. Lawrence community stakeholders identified litter and trash as one of their top priorities to be addressed through the "Making a Visible Difference" project.
The Clean River Project is how one of the partners is addressing this problem. This organization is dedicated to cleaning up the Merrimack River, for more information on their work, go to: http://www.cleanriverproject.org.
EPA's Trash-Free Waters program is reducing the volume of trash entering U.S. waterways. Common trash from consumer goods makes up the majority of what eventually becomes marine debris, polluting our waterways and oceans. Plastics in the aquatic environment are of increasing concern because of their persistence and effect on the environment, wildlife, and human health.