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Subbasins - Unkety Brook
Geographic & Ecosystem Characteristics | Land Ownership & Land Use Patterns
Major Water Resource Issues | Recreation & Priority Habitat Areas
Resource Protection Goals & Recommended Actions

Land Area: 6.9 sq miles
Primary Municipalities: Dunstable, Groton
Permanently Protected Land Area: 619 acres or 26%
Limited Protection Land Area (Chap. 61, etc.): 534 acres

% Imperviousness: approximately 6.6%
Land Use: 72% forest, 10.5% residential, 9.5% ag/open, 4.5% water
# of MA NHESP Priority Sites: 4
# of discharge permits: 0
Location within the Nashua River Watershed Water Resources Habitat Analysis
Open Space Water Resources Natural Heritage
Limited Protection Water Resources Recreation

Geographic Overview and Ecosystem Characteristics: This subbasin1 predominantly lies in the communities of Dunstable and Groton, with small extension into Pepperell. Located in the Southern New England Coastal Plains and Hills ecoregion2 of central Massachusetts, Unkety Brook flows into the Nashua River downstream of the Pepperell Wastewater Treatment Facility just a mile south of the New Hampshire line. Route 113 passes through this subbasin. Streamflow, as in most of New England, has significant seasonal changes3. The southern half of the eastern boundary of this subbasin is defined by a northeast-southwest running ridgeline.

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Land Ownership and Land Use4 Patterns: The land-use pattern is 50% forest (hardwood mixed with softwood) or wetland. Low-density residential settlement as well as concentrated settlements and strip development located near town centers and along major roads account for 16% residential use. A relatively high percentage, 16%, of total land area is agriculture and/or open space. Indeed, a very low percentage (6.6%, the lowest of all 22 Nashua River subbasins) of total impervious surfaces5 — namely, paved areas such as streets, driveways, and parking lots — for this subbasin indicates that issues of compromised stormwater and other non-point sources of contaminants6 (for example: pesticides, fertilizers, oils, asphalt, pet wastes, salt, sediment, litter and other debris) are not an immediate pressing concern.

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Major Water Resource Issues: Unkety Brook is classified as a Class B* waterbody and is a warmwater fishery. It headwaters are in Groton to the east of Chicopee Row north of the Chestnut Hills with another unnamed tributary emerging at the western base of the Horse Hill ridge. It flows through significant wetlands where it is exposed to direct sunlight, and lacking dramatic relief in its bed is therefore slow moving. Some new neighborhood development on adjacent upland may influence the water quality in the Brook. Polluted runoff and sedimentation is an increasingly serious issue in rapidly developing communities.

A shoreline survey was conducted by the Unkety Brook Stream Team in the spring of 1997. In short, its findings were that Unkety Brook: "is a wonderful resource for the Town of Dunstable and provides excellent riparian and aquatic habitat. The Brook is also threatened in many places from non-point source pollution, new construction and damaging agricultural practices." At the time, manure piles as close as 50 feet from the Brook at a farm, was considered noteworthy as were sections on the brook containing the invasive plant* purple loosestrife. One other major problem was at a farm where animals had open access to the brook causing sedimentation and damaging riparian vegetation. Nashua River Watershed Association's Volunteer Water Quality Monitoring Program has noted that Unkety Brook shows perennially low dissolved oxygen (DO) levels probably due to slow flow and increased oxygen demand in wetland areas. In some areas the DO levels are below that necessary to support even warm water fishes.

A medium-yield aquifer underlies a portion of this subbasin underlying the southern half of Unkety Brook. There are no major waterbodies, no major water withdrawals, nor any NPDES* permits in this subbasin.

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Recreation and Priority Habitat Areas: The most significant permanently protected areas in this subbasin are: the New England Forestry Foundation's (NEFF) Wharton Plantation, the Larter Family Agricultural Protection Restriction in Dunstable, and a string of Groton Conservation Commission holdings (Ripley Forest and Floyd/Groton Hills Conservation Areas). The Department of Environmental Protection's (DEM) 1983 Scenic Inventory Protect identified a small section in the southwest portion of this subbasin as contributing "distinctive" scenic character to the entire region. Less than a mile of the 12 mile-long Ayer to Dunstable Rail Trail, owned and managed by the Department of Environmental Protection, is located in the northernmost portion of this subbasin. This Rail Trail is just being constructed as a combined bicycling, walking, and bridle trail.

Nearly all of this subbasin is considered to be a Natural Heritage and Endangered Species Project (MA NHESP) BioMap core area7 . There are three state-designated MA NHESP Rare Wetlands Wildlife Habitat areas in this subbasin, which are designated Priority Habitat areas as well. These are: along Unkety Brook in southwestern Dunstable; and two nearly adjacent sights to the north and east of Chestnut Hills and south of Baddacook Hill in Groton. A fourth MA NHESP Priority Habitat area is located along the power line straddling the Groton-Dunstable border. This entire subbasin falls within the proposed Petapawag Area of Critical Environmental Concern (ACEC)8 nomination.

Two habitat protection focus area identified in the Nashua River Habitat Assessment Report (MAS, 2000) are:

  1. Horse Hill-Baddacook Hill: an area on the watershed boundary in Groton and Dunstable covering most of the southeastern portion of this subbasin which includes NEFF's Wharton Plantation as well as the Town of Groton Conservation Commission and Water Department, and the Groton Conservation Trust.
  2. Hound Meadow Hill-Hawk Swamp: the lightly developed northwestern corner of Dunstable important for its role as buffer for the Unkety Brook and associated wetlands and their adjacent wooded uplands. Hawk Swamp, which is bisect by Route 113, is a spruce-fir boreal swamp, and an example of a natural community type near the southern end of its range. Unkety Brook has been identified as exceptional habitat for aquatic wildlife. Priorities include the low land adjacent to Unkety Brook. Another priority for protection of a riparian corridor habitat is east of River Street.

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Resource Protection Goals and Recommended Actions

GOAL: Protect wildlife habitat and migration corridors in the subbasin.

  • Create a riverside greenway and insure habitat preservation, especially for state-listed threatened species such as the wood turtle.
  • Sponsor local events to raise public understanding about native wildlife and the impacts of development patterns on ecosystem and habitat integrity.
  • Work with local conservation commissions to gain their backing of natural resource and habitat inventories.

GOAL: Protect high-priority open space, vistas, and community character in the subbasin.

  • Encourage the use of MA Executive Order 418* funding for Open Space and Resource Protection Plans for each Massachusetts community in this subbasin.
  • Conduct public education sessions to promote local passage of Community Preservation Act*.
  • Work toward ideal of at least 25-50% protected open space in each municipality. Determine which Chapter 61, 61A and 61B properties to pursue Right of First Refusal* options on if the opportunity arises.
  • Work with municipal officials to develop subdivision standards that require proponents to devote at least 50% of land (not including already undevelopable wet or steep land) for open space conservation and encourage mixed-use development and cluster zoning by-right bylaws.

GOAL: Increase recreational opportunities throughout the subbasin.

  • Educate the public and municipal departments (especially DPWs) on efforts relating to invasive species identification and removal.
  • Support efforts of the Squannassit Regional Reserve Initiative* (facilitated by the NRWA) and the Petapawag nomination which encompasses much of this subbasin.

GOAL: Improve water quality in the subbasin.

  • Help develop and disseminate Best Management Practices (BMPs)* for small-scale, hobby type agricultural operations.
  • Identify any WMA withdrawals in this subbasin.
  • Identify underground storage tanks (USTs) and work to have them removed.

GOAL: Reduce potential negative effects of some development in this subbasin.

  • Monitor development along the banks of Unkety Brook to ensure building practices are sensitive to riparian habitat and water quality considerations.
  • Help local volunteer board members responsible for development and land-use rulemaking and enforcement get technical assistance and information regarding techniques to control/guide land use and development balanced with adequate resource protection (e.g., Citizens Planner Training Collaborative9 workshop offerings).
  • Increase or establish staff hours for municipal conservation agents to more effectively monitor construction sites runoff and assist with the preparation of bylaws such as erosion-sedimentation controls.

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* See glossary.

1 For this Plan, subbasins were delineated and analyzed using USGS defined boundaries which sometimes are truncated at the gaging station and may not appear to be consistent with topographically determined drainage areas.

2 The Coastal Plains and Hills ecoregion is an area with generally similar soils, vegetation, shape of the land, climate, and bedrock geology (glacial tills and outwash deposits). The Commonwealth of Massachusetts considers this physiographic region the "Central Upland" region.

3 Corresponding to seasonal stream flow changes are notable spikes in bacteria levels during summer and fall. Seasonal cycles of high bacteria concentrations may be attributed to decreased dilution during summer months, when tributary flows are lowest. (Wachusett Reservoir Watershed Protection Plan Update 1998, pp. 2-29)

4 "Land Use" description at

5 According to the Center for Watershed Protection's Rapid Watershed Assessment Handbook protocol, an area with less than 10% (8 - 12%) impervious surfaces is considered "partially threatened"; less than 8% is considered "sensitive" or what one would say is a relatively pristine environment;" 12 - 20% is considered "threatened"; and more than 20% is considered "non-supporting" or urbanized. The figures cited in the narrative are based on NRW Estimated Impervious Cover by Sub-basin based on '85/'92 Land Use: MDC '98 Methods Estimate by Bruce Bayne and Jo Anne Carr of the EOEA Nashua River Watershed Team.

6 Primary pollutants of concern in stormwater are suspended solids, nutrients, metals, oil and grease, temperature and bacteria. The sources of bacteria in urban settings are typically human litter and animal waste left on driveways, lawns, commercial and residential streets, parking lots and rooftops.

7 BioMap url:

8 ACEC url:

9 Citizen Planner Training Collaborative (CPTC)

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