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Pine Meadow Pond

Pine Meadow Pond
(aka Erskins Pond, Upper Flannagan Pond) 

  • 34 acres
  • A shallow pond with an average depth of 6-7 feet
  • Artificially created by the impoundment of water at a dam close to Oak Ridge Drive, for use by a sawmill, hence a ‘flooded wet meadow’
  • Perimeter approximately 1 mile
  • Part of the 538 square mile Nashua River Watershed
  • Located within the Petapawag ACEC (Area of Critical Environmental Concern)
  • Receives its water from Pine Meadow Brook, which comes from a source near Half Moon Road in Groton
  • Pine Meadow Brook just upstream a bit now features Rock Meadow Pond, another flooded wet meadow by beaver dams
  • Water flows from Pine Meadow Pond at its southwestern tip over a human-made dam and then through a culvert a short distance away in order to pass underneath Oak Ridge Drive and enter Flannagan Pond’s northwestern corner
And if you want to learn more…

 

General Description and History
Pine Meadow Pond is part of the chain of hydrologically-connected ponds and streams that bisect Ayer and eventually convey their waters into the Nashua River:  Long Pond > Sandy Pond > Flannagan Pond (fed into also by Pine Meadow Pond) > Balch Pond > Grove Pond > Plow Shop Pond > Nonacoicus Brook > Nashua River.

Left in its natural state, Pine Meadow Pond would have remained a brook passing through what used to be known as Pine Meadow, back when Ayer was still part of the Town of Groton (until 1871).  Further upstream, a brook still feeds into this area, flowing from Rock Meadow Pond whose impoundment is the result of industrious beavers and their stick-and-mud dams.  In turn, the water in Rock Meadow Pond has its source further north, in swamps on the north side of Snake Hill, located in present-day Groton near Half Moon Road. 

Pine Meadow Pond attained its pond status after it was dammed at its outlet at the south end, near Oak Ridge Drive, transforming Pine Meadow into Pine Meadow Pond.  Historical documents written in 1890 include references to the remains of a sawmill constructed at this location prior to 1715.  Another sawmill was constructed at the same location in 1903.  The property was sold in 1937 and the mill was destroyed in 1939 but the new owners rebuilt the dam and have kept the meadow flooded ever since.

Pine Meadow Pond is bordered on 3 sides (west, north, and east) by the 129-acre Town-owned Pine Meadow Conservation Area that provides walking trails as well as boat ramp access (for canoes and kayaks) to the pond from off of Groton Harvard Road near the trailhead.  Much of Pine Meadow Pond’s shoreline is therefore undeveloped, with only a few residences located at the very southern tip of the pond.

To get a sense of how much water is impounded upstream from Pine Meadow Pond, and how much force is contained by that water, consider this:  In 2011, the beaver dam at the upstream outlet of Rock Meadow Pond had a catastrophic failure, suddenly releasing an estimated 19 million gallons of water that rushed downstream through Pine Meadow Pond with such force that it took out a section of Oak Ridge Drive.  The force of this of this flood was enough to raise not only the water level in Flannagan Pond, but also through backwashing upstream, the level of Sandy Pond for a time until the floodwaters were able to subside and dissipate along their normal chain of flow.  The Department of Public Works then had to replace the culvert and rebuild that portion of Oak Ridge Drive so that it was again passable.

Much of Pine Meadow Pond is comprised of a very dense assemblage of native floating-leaf as well as submerged aquatic vegetation.  Plant growth is densest at the more shallow northern end where it gradually transitions into a wet meadow/marsh community of plants.  The southern end of the pond ranges from very dense growth in the near-shore areas to sparse growth in the deeper central area where the water is more open.  The Ayer Conservation Commission includes this pond within its annual aquatic vegetation maintenance program, along with Sandy and Flannagan ponds.  For Pine Meadow Pond, this program focuses on the eradication of non-native aquatic plants (primarily variable leaf milfoil and curly-leaf pondweed) as well as reducing the excessive overgrowth cover and density of native water lilies throughout much of the pond.

Trophic Status
Ponds, lakes and other surface waterbodies can be evaluated on scales that rate their trophic status.  This status indicates the amount of ‘biological productivity’ (or total weight of living biomass at time of measurement) that a waterbody sustains.  Biomass in a waterbody is usually dominated by either aquatic vegetation or algae.  Waterbodies can range from oligotrophic – less biomass/’good’ water quality; mesotrophic – moderate biomass/’fair’ water quality; and eutrophic to hypereutrophic – high/dense biomass/’poor’ water quality.  Too many ‘nutrients’ in a waterbody (especially from phosphorus and nitrogen runoff from stormwater, nearby fertilizer use, septic systems, etc.) will lead to an increase in plant and/or algae growth and a decrease in water quality as the process of eutrophication continues.  While eutrophication is a natural process of nutrient enrichment in aquatic ecosystems that takes place gradually over time, it can be dramatically accelerated by the impact of human activities that increase the flow of nutrients into waterbodies and their surrounding watershed.

According to the Geosyntec Consultants study of Ayer Ponds completed in 2016, as measured by the Carlson Trophic State Index (TSI) model, Pine Meadow Pond is rated as mesotrophic.  The Carlson TSI uses water clarity and measurements of Total Phosphorus (TP) and Chlorophyll-a to make its assessment.  A different model for evaluating eutrophication is the Vollenweider model which uses measurements of a pond’s ‘flushing rate’, the TP load entering the pond from external sources, and the internal TP concentration already there {i.e. from sediment and plant decomposition).  In spite of the density of vegetation on Pine Meadow Pond, the Vollenweider model is in agreement with the assessment of Pinemeadow Pond as mesotrophic.  The lack of human development around most of this pond undoubtedly has contributed to its maintaining a healthier mesotrophic state..

Impairment
The Federal Clean Water Act (effective in 1972) governs water pollution in the United States, and requires states to identify waterbodies that do not meet EPA standards and are designated as “impaired.”  Pine Meadow Pond is not listed as an impaired waterbody in Massachusetts.

This sign project was funded by a community grant from the Nashua, Squannacook, and Nissitissit River Wild & Scenic Stewardship Council.