4.2 Groundwater, Surface Water, and Endangered Species Protection

Groundwater, Surface Water, and Endangered Species Protection

Quick Answer: Water contamination occurs via point sources (spills, back-siphoning) and non-point sources (runoff, leaching). Coarse sandy soils low in organic matter have high permeability and pose the highest leaching risk. Massachusetts protects drinking water under 333 CMR 12.00 by restricting pesticides on the Groundwater Protection List within Zone II and Interim Wellhead Protection Areas.

Protecting water resources is a paramount concern for pesticide applicators in Massachusetts. The state's glaciated geology, shallow water tables, sandy aquifers (such as those on Cape Cod and in the Connecticut River Valley), and extensive network of surface waters make it highly vulnerable to contamination. Pesticides can enter water sources through two primary pathways: point sources and non-point sources.

Water Contamination Pathways: Point vs. Non-Point Sources

Point source contamination occurs when a pollutant enters the water from a single, identifiable location. In pesticide applications, point sources are almost always the result of human error or improper handling practices. Common examples include:

• Spills: Accidental spills of concentrated or diluted pesticides during mixing, loading, or transport.
• Back-siphoning: Occurs when the spray hose is submerged in the spray tank liquid during filling, and a drop in water pressure draws the chemical back into the water supply. Applicators must maintain a physical air gap (keeping the hose nozzle well above the tank rim) or use an approved backflow preventer device.
• Improper disposal: Dumping excess spray mix, tank rinsates, or untreated wastewater into storm drains, sewers, sink drains, or directly onto the soil.
• Equipment washing: Washing spray equipment in areas where runoff can enter a wellhead, storm sewer, or surface water body.

Non-point source contamination refers to diffuse, widespread movement of pesticides into water bodies from treated areas. This occurs over a broad geographic area and is influenced by natural processes rather than a single site-specific event. Runoff from agricultural fields, suburban lawns, golf courses, or forestry applications carrying pesticides into streams and ponds is a classic example of non-point source pollution. Leaching of agricultural chemicals through the soil profile into underlying aquifers over thousands of acres is also non-point source contamination.

Soil Properties Affecting Leaching

Once a pesticide is applied to the soil, its movement is governed by the physical and chemical properties of the soil itself. The three most critical soil properties are texture, organic matter, and permeability.

• Soil Texture: Texture is determined by the relative proportions of sand, silt, and clay. Sandy soils have large, coarse particles and large pore spaces. They provide very little surface area for chemical binding and allow water to drain rapidly, making them highly prone to pesticide leaching. Silt soils have intermediate particle sizes and moderate leaching potential. Clay soils consist of tiny, tightly packed particles with a massive surface area. Clay binds pesticides strongly (adsorption) and has very small pores, which slows water movement and reduces leaching, though it increases the risk of runoff due to slow water infiltration.
• Organic Matter: Soil organic matter consists of decaying plant and animal residues. Organic matter has a very high capacity to chemically bind (adsorb) pesticides. Soils rich in organic matter act like a sponge, trapping pesticides near the surface where soil microorganisms can break them down. Sandy soils with low organic matter content have the highest vulnerability to leaching because they lack both the physical filtration of clay and the chemical binding sites of organic matter.
• Permeability and Infiltration: Permeability refers to the ease with which water moves downward through the soil profile. High permeability correlates directly with rapid leaching. Infiltration is the rate at which water enters the soil surface. Low infiltration rates (common in compacted clay soils) reduce leaching but increase surface runoff.

In addition to soil properties, the chemical characteristics of the pesticide itself dictate leaching risk. Applicators must look out for products with high water solubility, low soil adsorption (a low adsorption coefficient, or Koc value), and high persistence (a long half-life). These characteristics make a pesticide highly mobile and slow to degrade, creating a significant threat to groundwater.

Massachusetts Groundwater Protection (333 CMR 12.00)

To safeguard drinking water, the Massachusetts Department of Agricultural Resources (MDAR) enforces 333 CMR 12.00, which regulates pesticide applications in the protection of groundwater sources of public drinking water. The regulation focuses on protecting Zone II areas and Interim Wellhead Protection Areas (IWPAs).

A Zone II is the primary recharge area for a public drinking water well pumping 100,000 gallons per day or more, as officially designated by the Massachusetts Department of Environmental Protection (MassDEP). An IWPA is a temporary circular protection zone established around a public water well when a formal Zone II has not yet been delineated.

Under 333 CMR 12.00, MDAR maintains a Groundwater Protection List (GPL), which is updated annually. The GPL includes active ingredients (such as atrazine, simazine, and metolachlor) that have been identified as potential groundwater contaminants due to their environmental mobility and persistence.

The application of any pesticide containing an active ingredient on the GPL is highly restricted within a Zone II or IWPA. To legally apply these products in these protected areas, the applicator must:

1. Verify that no viable, effective alternative pest control method exists.
2. Use a department-approved Integrated Pest Management (IPM) program tailored to the site.
3. Operate under an approved Pesticide Management Plan (PMP) that outlines specific practices to prevent groundwater contamination.

Applicators can determine if a site lies within a Zone II or IWPA by consulting MassDEP maps, local Boards of Health, or using MDAR's online mapping tools before scheduling applications.

Endangered Species Protection

Pesticides can also threaten rare, endangered, or threatened wildlife and plant species. Applicators must comply with both federal and state laws designed to protect these organisms.

At the federal level, the Endangered Species Act (ESA) is implemented by the EPA through the Bulletins Live! Two (BL2) online database. Before applying any pesticide, the applicator must access the BL2 system, enter the product's registration number, the location of the application site, and the month of the scheduled application. The system generates a geographic bulletin showing whether any pesticide use limitations are in effect for that area. If a bulletin contains restrictions, they are legally binding and enforceable under federal law.

At the state level, the Massachusetts Endangered Species Act (MESA) is administered by the Natural Heritage and Endangered Species Program (NHESP), a division of MassWildlife. NHESP maps state-listed rare species habitats, vernal pools, and key ecological areas. Applicators working near designated sensitive habitats must ensure that their activities do not result in off-target drift or runoff that could harm protected species, particularly in aquatic environments or wetlands.