Water Sources and Watershed Protection
Massachusetts systems draw from bedrock and gravel wells, reservoirs, rivers, and infiltration galleries. This domain tests whether you can name a source type, define its protection zones, and connect watershed conditions to raw-water quality and treatment requirements.
Source types and protection areas
- Groundwater, surface water, and groundwater under the direct influence of surface water (GWUDI). A GWUDI determination brings filtration and disinfection obligations similar to surface water.
- MassDEP Source Water Assessment Program (SWAP) reports rank each source's susceptibility to contamination; sanitary surveys add field findings.
- Groundwater zones: Zone I is a 400-foot radius around the well; Zone II is the contributing recharge area from an approved MassDEP groundwater model; Zone III is the rest of the contributing watershed. Where no Zone II is approved, an Interim Wellhead Protection Area based on pumping rate is used.
- Surface water zones: Zone A (400 feet from the bank or edge of the reservoir), Zone B (0.5 mile), Zone C (the remainder of the watershed).
Protection tools
Land acquisition and conservation restrictions, zoning overlays, stormwater and MS4 controls, Title 5 septic setbacks, road-salt and snow-dump management, and agricultural best management practices.
Worked example
Zone I area for a well: A = πr² = 3.1416 × 400² = 502,655 ft². Dividing by 43,560 ft²/acre gives about 11.5 acres. Because the radius is squared, doubling the radius quadruples the protected area - a fast mental check.
Traps that cost marks
Mixing the groundwater Zone I/II/III labels with the surface-water Zone A/B/C labels. Treating Zone I as a 100-foot setback. Forgetting that a spring or infiltration gallery may be classified GWUDI, which changes treatment requirements. Confusing SWAP susceptibility ranking with an actual regulatory violation.