Duxbury Septic Analysis
BarrierGap analysis of Duxbury's Board of Health septic regulations against the Title 5 baseline (310 CMR 15.000). 4 provisions exceeding state baseline. 1 barrier identified.
Duxbury Septic Regulation Analysis
Board of Health Supplementary Rules & Regulations to Title 5
Last reviewed: March 3, 2026
What This Means
Massachusetts law (M.G.L. c. 111, § 31) authorizes local Boards of Health to adopt septic regulations stricter than the state Title 5 baseline. Duxbury has exercised that authority — its supplementary rules exceed Title 5 minimums in at least four areas relevant to ADU construction: groundwater separation, wetland setbacks, private well setbacks, and irrigation well setbacks. These stricter standards are legally authorized and reflect local environmental and public health priorities. However, because ADUs are treated as new construction, variance relief is not available — unlike virtually every other septic project that comes before the Board. A homeowner may have the right to build an ADU under state zoning law, but their lot may not support a septic system under the town’s Board of Health rules.
Gap Comparison
| Provision | Title 5 | Local Rule | Gap |
|---|---|---|---|
Groundwater Separation | 5 ft above high groundwater in fast-perc soils; 4 ft in slower soils | 6 ft above max high groundwater in fast-perc soils (≤2 min/inch) | +1 foot above state minimum |
Wetland Setback | 50 ft from bordering vegetated wetlands | 150 ft from bordering vegetated wetlands | 3× the state minimum (+100 ft) |
Private Well Setback | 100 ft (reducible to 50 ft with water quality testing) | 150 ft from private drinking water wells | +50 ft above state minimum |
Irrigation Well Setback | 25 ft from irrigation wells | 100 ft from irrigation wells | 4× the state minimum (+75 ft) |
No Variance Relief for ADUs | No specific ADU septic provision in Title 5 | ADUs = new construction; must meet all local standards without variances | Variance pathway unavailable for ADU projects |
Bedroom Definition | Room providing privacy, intended primarily for sleeping | Any room providing privacy with at least one window = bedroom for flow calculation | None identified |
Data Provenance
Regulatory layer: Board of Health Supplementary Rules & Regulations to Title 5
State baseline: 310 CMR 15.000 (Title 5 of the State Environmental Code)
Local authority: M.G.L. c. 111, § 31
Reviewed: March 3, 2026
Sources
Methodology
This analysis compares local Board of Health supplementary rules against the state Title 5 baseline (310 CMR 15.000). Unlike zoning — where Chapter 150 preempts certain local restrictions — local Boards of Health are explicitly authorized under M.G.L. c. 111, § 31 to adopt standards stricter than Title 5. Exceeding the state baseline is not a legal deficiency. This analysis measures the gap between local and state requirements and assesses practical impact on ADU feasibility. It does not constitute legal advice.