Somerville, MA Landscaping Rules: Rainwater Harvesting (2026)
Key Facts
- Credit type
- Optional Green Score bonus, not mandate
- Threshold
- 50% of irrigation from harvested rainwater
- Bonus multiplier
- 0.1, per Table 10.4.2
- Applies to
- New principal buildings, substantial renovations
- Administered by
- Building Official, §10.4.4.b
- Governing table
- Table 10.4.2 Green Score Bonuses
Summary
Somerville's Green Score standard for new construction and major renovations awards a bonus credit toward the required landscape performance score when at least half of a site's irrigation comes from harvested rainwater. Table 10.4.2 lists '50% of irrigation is harvested rainwater' as a 0.1 multiplier bonus under §10.4.5.b.
b. Bonuses
i. Review Boards may establish additional bonuses than those listed on Table 10.4.2 to achieve other city policy objectives based on the recommendations of the Director of Public Space & Urban Forestry.
Table 10.4.2 Green Score Bonuses Credit Multiplier Bonus Credits Publicly visible landscape 0.1 Native species 0.1 High value species 0.1 50% of irrigation is harvested rainwater 0.1 Food cultivation 0.1 De-paved Lot area 0.1
ii. Each additional bonus may have a multiplier up to one-tenth (0.1) for each bonus.
Full Breakdown
Green Score, defined in Article 10.4, is Somerville's environmental sustainability performance standard: new principal buildings and substantial renovations of a principal building must achieve a minimum weighted score, calculated under §10.4.5, by adding up the weighted value of every proposed landscape element and dividing by total lot area. Section 10.4.5.b lets the Review Boards stack additional multipliers onto that base calculation using the Bonus Credits in Table 10.4.2, and rainwater harvesting is one of six listed bonus credits: publicly visible landscape, native species, high value species, '50% of irrigation is harvested rainwater,' food cultivation, and de-paved lot area, each worth a 0.1 multiplier.
The rainwater credit is not a standalone permit requirement or a mandate to install a cistern; it is an optional way for a developer to raise a project's Green Score toward whatever minimum applies to that building type and district. Section 10.4.5.b.ii lets Review Boards cap each additional bonus at one-tenth (0.1), so the rainwater-irrigation bonus stacks with the other five bonus credits and with the base Table 10.4.1 landscape-element multipliers, such as soils, groundcovers, plants, trees, and engineered features like rain gardens and bioswales, to help a project reach compliance. The Building Official administers Green Score compliance under §10.4.4.b, and applicability is limited under §10.4.3 to new principal buildings and substantial renovations, so an ordinary remodel that is not a substantial renovation is not required to hit any Green Score target at all.
Violations & Fines
There is no separate penalty for skipping the rainwater-harvesting bonus itself, since Table 10.4.2 credits are optional; the enforceable requirement is meeting the overall Green Score minimum for the building type under §10.4.4.a. A project that submits a landscape plan claiming the bonus without irrigating at least 50% from harvested rainwater risks the Building Official rejecting the calculation and withholding approval until the score is corrected without that credit.
Frequently Asked Questions
Does Somerville require rainwater harvesting for landscaping?
What score bonus does harvesting rainwater earn in Somerville?
Which projects have to calculate a Green Score at all?
Sources & Official References
Other rules in Somerville
Compare Somerville to another location·View the Massachusetts landscaping rules overview
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