January 13, 2015 Wayland Surface Water Quality Committee (WSWQC) 59 Moore Road Wayland, MA 01778 thomas.largy@verizon.net Via Email Re:
2014 Summary Report Water Chestnut Harvesting, Heard Pond, Wayland, MA
Dear Committee Members: In accordance with the Order of Conditions, DEP File No. 322-0678, for the removal of Water Chestnut in Heard Pond, we are pleased to provide this summary report of the 2014 management program. On June 30, 2014, a pre-harvesting survey was conducted by Jeff Castellani of Lycott Environmental (Lycott) to assess the density and distribution of Water Chestnut (Trapa natans). Water Chestnut plants were observed consistently around the shoreline within the floating-leaf and emergent aquatic vegetation and extended up to ten feet into the open water. More specifically, Water Chestnut growth was observed at a density of approximately a dozen plants per 100’ x 100’ grid on the west, north and east shorelines. The south cove exhibited similar densities and extent except scattered growth was observed throughout three-fourths (¾) of the south basin in the open water. Excluding the southeast corner where the river runs adjacent to the wetlands, the infestation would be described as scattered coverage of trace to light density (0-20) or up to 20% density. The only area that would be characterized as moderate density was in the opening to the wetland area in the southeast. Many of the Water Chestnut plants co-existed within other species of floating-leaf vegetation primarily, White Water Lily (Nymphaea odorata), and emergent vegetation primarily Pickerelweed (Pontederia cordata) and Buttonbush (Cephalanthus occidentalis). Based on these observations, the 2014 Water Chestnut infestation appeared to be broader in density however consistent in coverage than that observed in 2013. On Heard Pond, nutlet germination and rosette development typically takes place in mid to late June. The majority of rosettes had surfaced by the June 30th survey, rosettes were 4” to 8” in diameter with some still suspended in the water column. In general, Water Chestnut germination and rosette growth observed on area water bodies in the spring of 2014 were advanced compared to the infestation on Heard Pond. However, those area water bodies are nutrient rich river systems and are typically ready for an initial harvest by the second week of June. Hardy Pond in Waltham Massachusetts, with a similar mechanical / hand harvest history, exhibited the same phenomenon as Heard Pond in recent years with respect to a fluctuation in Water Chestnut plants observed / harvested; 2012 – 835 plants, 2013 – 4,320 plants, and 2014 – 1874 plants. Based on the growth present at the time of the survey, it was recommended the hand-pulling event commence the second week of July.
In accordance with the management plan approved by the WSWQC, removal of Water Chestnut was to be accomplished by the hand-pulling method, supplemented by mechanical harvesting, if necessary. A base of operations was designated on the southwestern shoreline of Heard Pond off of Pelham Island Road. On July 11, Lycott commenced physical removal of Water Chestnut from Heard Pond utilizing only the hand-pulling method. Hand-pulling commenced in the southeast wetland area for three days and proceeded to the south cove perimeter, south cove open water and then the perimeter of the remaining shoreline. A follow-up and final hand pulling effort was conducted in each area. Due to the lower than mean water level experienced at Heard Pond this season, wading was employed to access the wetland and shoreline areas. The shallowness of the water in the infested areas coupled with the density of the floating-leaf and emergent aquatic vegetation necessitated several sweeps of the respective areas to spot the Water Chestnut plants, particularly in the southeast wetland area. On September 4, 2014, Jeff Castellani performed the annual post-harvest survey of Heard Pond for Water Chestnut plants. Thirtynine rosettes, approximately 8” in diameter, still flowering with nutlets intact, were observed and removed while conducting the inspection. Over the course of the 2014 management season, a total of 5876 plants with rosettes 6” to 12” in diameter were removed, bagged and disposed by Lycott during nine hand-pulling days as outline below. The WSWQC intern also removed an additional 123 plants during three visits and 39 plants were removed by Lycott during the final inspection. A summary of the hand-pulling events is provided in the following table: Date
No. of Plants
7/11/14
1200
Southeast wetland area
7/14/14
1900
Southeast wetland area
7/15/14
1200
Southeast wetland area South cove perimeter
7/16/14
500
South cove open water
7/17/14
200
South cove open water Open water perimeter of pond
7/18/14
200
Open water perimeter of pond
7/21/14
50
Pickerel weed and lily perimeter (WSWQC intern)
7/24/14
241
Pickerel weed and Lily perimeter
7/25/14
274
Pickerel weed and lily perimeter
8/6/14
53
Southeast cove wetland area (WSWQC intern)
8/8/14
161
Final sweep--perimeter and southeast wetland o 13-west shore o 117-southeast wetland o 31-Pickerelweed & Lily
8/22/14
20
24 additional spotted but intern could not reach from boat – perimeter and southeast wetland
9/16/14
39
Within Water Lily along shoreline (post-harvest survey)
6038
1/13/2015
Location(s)
2014 Total of Plants Harvested
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The combined thirteen days of hand-pulling and inspection, conducted by Lycott and the WSWQC intern yielded 60 bags of plant material, totaling approximately 1.5 tons and/or 6038 plants. The plant count (691 in 2013 versus 6038 in 2014) increased by 873.8 percent. A summary of the yearly tonnage of plants removed from Heard pond since 2008 is provided in the following table:
Tons Of Plants Harvested 2008 to 2014 9
8.4
8
Tons
7 6 5 4
3.2
3 1.5
2 1
0.21
0.27
0.12
0.04
2010
2011
2012
2013
0 2008
2009
2014
Harvest Year
Much discussion and conjecture transpired trying to understand the sharp spike in the number of Water Chestnut plants observed this season. Below is a summation of the factors that may have contributed to the increase in the number of nutlets that germinated this season:
The lower than mean water level this season, allowed sunlight to penetrate into the sediment that may have spurred a higher percentage of nutlet germination. Last season’s climate conditions, a wet, cool spring, higher than mean water level in the pond during the summer months and the general tannic color of the pond’s water may have contributed to the lower number of Water Chestnut plants last season. Dense floating-leaf and emergent aquatic vegetation cover may also be stalling nutlet germination. Missing just one plant in a harvest season could add up to 18 nutlets to the existing seed bed. Coupled with the understanding that nutlets are viable for up to 12 years, the areas that we are predominately hand harvesting were not intensively hand harvested until 2007. Although we have discounted the possibility of the adjacent Sudbury River depositing nutlets into the wetland area, waterfowl and wildlife may have transported additional seeds into the pond and wetland areas. Areas from a short distance with heavy floating-leaf and emergent vegetation coverage may visually appear to be Water Chestnut free, even by the trained eye.
Going forward, wading will be employed and several sweeps of the pond to prevent a Water Chestnut plants from being left behind. The water level will also be monitored to aid in scheduling the initial, followup and final hand-pulling days to maximize the ability to access the wetland area, as well as the densely vegetated littoral areas of the pond. 1/13/2015
3
It is anticipated that Water Chestnut coverage and density will decline in 2015. With the addition of the wading effort in the southeast wetland area, Lycott anticipates six to eight days of hand-pulling will be needed during the 2015 season to continue the eradication process of Water Chestnut in Heard Pond. Please contact us if you have any questions or require additional information. Sincerely,
Jeffrey J. Castellani Director of Mechanical Operations JJC
1/13/2015
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