Woodridge Lake Long -Term Invasive Weed Control Plan

Transcription

1 Woodridge Lake Long -Term Invasive Weed Control Plan

2 Outline Our invasive weed problems The plan a significant remediation effort followed up with effective maintenance Cost Safety of the aquatic herbicide fluridone Conclusion References and additional information

3 Eurasian Watermilfoil The Problem State of Maine on Recreational Impacts Washington State on Lake Health State of Indiana on Property Value Impacts "The impacts of an [Eurasion Watermiloil] infestation have the potential to be devastating. Dense mats of Eurasian water-milfoil impair boating, fishing, and swimming. Reduced lake water quality is another concern. Eurasian watermilfoil adversely impacts aquatic ecosystems by forming dense canopies that often shade out native vegetation. Significant rates of plant sloughing and leaf turnover, as well as the decomposition of high biomass at the end of the growing season, increase the internal loading of phosphorus and nitrogen to the water column. Dense Eurasian watermilfoil mats alter water quality by raising ph, decreasing oxygen under the mats, and increasing temperature. Stagnant water created by Eurasian watermilfoil mats provides good breeding grounds for mosquitoes. A lake heavily infected with [milfoil] will be aesthetically displeasing which results in reduced property values

4 Curly-Leaf Pondweed (CLP) - The Problem State of Minnesota on Lake Health Curlyleaf pondweed (Potamogeton crispus) is a rooted submerged plant that quickly forms dense mats at the water surface of lakes and rivers in late spring and early summer... Mats interfere with boating, fishing, waterfowl hunting, and swimming. Summer die-offs can form windrows of decaying plants on shore, sometimes followed by algal blooms. Curlyleaf pondweed displaces native plant communities and decay can deplete oxygen levels, leading to fish kills and impacts on other aquatic life. K. Wagner Woodridge Lake Summary Report. The addition of curlyleaf pondweed to the lake adds another dimension to the management dilemma, and with substantial expansion observed in 2014, delaying aggressive management may carry great cost for future efforts or cause distinct impairment of habitat and lake use.

5 The impact of these two invasive weeds on our lake are not just recreational or aesthetic inconveniences, they are altering the biology of the lake. Both of these weeds have the potential to infest the entire littoral zone of our lake; which is everything from the shoreline out to a depth of about 20. These weeds grow profusely, generate enormous biomass that accumulates every year, settles to the bottom of the lake and then decays. As plants decompose, they generate nitrate which helps fertilize the lake bed for more growth. This process of decomposition removes oxygen from the water, which creates algae, stresses aquatic animals and negatively effects the water quality. If unchecked, the continued growth of these invasive weeds will accelerate the cycle of eutrophication which will reduce the quality of our lake and ultimately degrade itsrecreational value.

6 Our lake and invasive weeds 2005 to Fluridone utilized effectively to remediate milfoil (EWM) in the lake, even though the complete program was not followed No active program, limited EWM presence EWM presence increasing - LDC establishes drawdown & harvesting program 2008 to LDC manages the EWM problem with the use of deep drawdowns, mechanical harvesting, diver harvesting and a herbivore program. The two maps to the right represent the increase in milfoil between 2008 to Milfoil infestations have increased dramatically over this period. 1/3 of our lake does not support plant growth, so these maps represent a 70% increase of EWM in the regions of the lake that do. Curlyleaf pond weed (CLP) first appeared in 2013 and is slightly represented in the 2014 survey. In less than two years CLP has grown so dramatically that it is now the second most abundant plant in our lake - behind only milfoil. The two most prevalent plants in our lake are now invasive species. Field Survey 5/08/08 Field Survey 6/16/14 Field Survey 10/17/14

7 Percentage Cover of Plants in data zones Our lake needs help and it is our responsibility to care for it. The graph on the right shows the decrease in desirable plant cover and a corresponding increase in invasive plants in our lake from 2008 to At this point in time invasive weeds make up approximately 50% of the plant population of our lake. Remediating a lake that is dominated by invasive weeds is extremely difficult due to fewer native plants being available to re-establish the lake bed. A comprehensive lake management plan considers water quality, fishery and plant diversity and its foundation is a healthy, established native plant community. The issues that we must understand in order to avoid our lake from being further dominated by invasive weeds: Plant Cover in Littoral zone of our Lake Desireable Plant Cover Curlyleaf Cover Linear (Milfoil Cover) Milfoil Cover Linear (Desireable Plant Cover) Plant cover represents an estimate of the areal (twodimensional) cover on the lake bottom. Nature cannot displace the weeds without assistance and if they are not removed, they will expand the only variable is how much. When weeds are removed from an area, by any method, the remediated area will most likely become reinfested by the most aggressive growing plants in the lake, which unfortunately for us are milfoil & curlyleaf.

8 The Two Step Plan A long track record of success Step 1 involves a significant initial remediation program to substantially reduce the invasive levels to the point where. Step 2. efforts in subsequent years involve more minimal management efforts. Follow up efforts must be sustained and disciplined or the initial remediation effort is wasted. Step One involves using a pelletized form of the aquatic herbicide fluridone at a dosing of approximately 40 ppb in targeted treatments areas. The major advantages of this approach are: It will be effective throughout the lake and we can expect a 90% reduction of both EWM & CLP the year of treatment. There will be a reduced impact on the surrounding native vegetation. This will allow the native plants to re-establish themselves in the remediated areas more efficiently, making re-infestation of invasive plants more difficult. In subsequent years less intensive efforts are required. This map is a sonar survey of our lake performed on 10/17/14. Because EWM is the tallest growing plant in our lake, this is an excellent representation of the actual below surface infestation of EWM.

9 The Proposed 2-Step Integrated Plan 2015 Mechanical Harvesting as necessary 6.0 Drawdown (Mid Nov- Mid Jan) Step 1 - Remove 90% of the weeds 2017 Step 2 - Locate and remove remaining weeds 2018 and after Application of fluridone (3 to 5 treatments over a day period beginning in April) Utilize pelletized fluridone targeted to the problem areas; dispensed in 3 to 5 separate applications of ppb of Sonar pellets, resulting in a total of ppb being applied in the treated area over the day period. Since the pellets are time release formulations, we would not expect to see more than 10 ppb of fluridone in the water column at any one time No restrictions on swimming or any recreational activity. Restrictions on lawn watering consistent w/ WLPOA rules. Mechanical harvest if necessary 6.0 Drawdown (Mid Nov - Mid Jan). Comprehensive spring weed survey Diver harvest sporadic infestations Spot treat weeds with fluridone pellets if density warrants Mechanical harvest if necessary 6.0 Drawdown (Mid Nov - Mid Jan) Continued disciplined maintenance - which is effectively a continuation of the Step 2 efforts.

10 Cost Year Description Cost Low Range Cost High Range 2015 Mechanical Harvesting $15,000 $20, Mechanical Harvesting $0 $5,000 Targeted Treatment Fluridone $100,000 $120, Mechanical Harvesting $0 $5,000 Diver Harvesting $10,000 $25,000 Spot Fluridone Treatment (if required) $ 0 $20, Mechanical Harvesting $5,000 $10,000 Diver Harvesting $30,000 $30,000 Spot Fluridone Treatment (if required) $ 0 $20, Mechanical Harvesting $5,000 $10,000 Diver Harvesting $30,000 $30,000 Spot Fluridone Treatment (if required) $ 0 $20,000 Total 5 Year Cost $195,000 $315,000

11 Fluridone 30 Years of Effective Use Connecticut DEEP There are no human health concerns with the proper use of this chemical. The allowable drinking water level (150 ppb) is greatly in excess of common use rates (5-20 ppb), so that contact activities such as swimming do not have a waiting period after application. Targets and inhibits the unique chlorophyll-making ability of aquatic plants, not humans or other animals. A slow-acting systemic herbicide used to control milfoil, curly-leaf pondweed and other invasive weeds. Used at very low doses. Produced in slow release pelletized formulations, which can be better targeted to problem areas. Safety tested and approved for use by the United States EPA in years ago. Also tested by U.S. Agriculture Dept, other government bodies and many private institutions. Approved for use by the CT Dept. of Health Registered in all 50 states and Puerto Rico and is annually used in hundreds of waterbodies. Ken Wagner has recommended its usage many times. Expect to reduce milfoil and CLP by some 90%, with a long proven, and safe track record of doing so. Native, seed-bearing plants, will grow back. WL effectively used it in 2005 but did not build upon this success with a sustained second step maintenance plan.

12 The 65 Connecticut Towns where fluridone was used in 2013 Connecticut is a small state yet lakes in 65 of our towns used fluridone in 2013 because it is a very effective invasive weed management tool Ashford Avon Berlin Bethel Bethlehem Bloomfield Branford Brookfield Canterbury Chaplin Cheshire Colchester Danbury Darien Deep River East Haddam Easton Ellington Essex Fairfield Farmington Glastonbury Granby Greenwich Griswold Guilford Hamden Ivorytown Litchfield Middletown Monroe New Canaan New Milford Newington North Branford North Stamford Orange Plymouth Ridgefield Roxbury Salisbury Simsbury South Kent Southbury Southport Stamford Stonington Trumbull Union Vernon Bolton Wallingford Warren Waterford West Hartford West Haven West Redding West Simsbury Weston Westport Wethersfield Wilton Woodbridge Woodbury Woodstock

13 Comparative Analysis Because fluridone is a slow acting systemic herbicide, it is utilized at very low doses. Fluridone is not acutely toxic(ⁱ) and its intended dosing is a fraction of what is encountered in daily life activities. This table identifies the specific utilization of a chemical and the concentration used to highlight the risks associated with toxicity and exposure. Utilization Chemical ppb (parts per billion) WL Weed Remediation Program Fluridone 40 WL Swimming Pool Sodium hypochlorite (Chlorine) 2,300 NYC Municipal Water Chlorine 630 Fluoride 800 (ⁱ) PAN Acute Toxicity rating for Fluridone - not acutely toxic (lowest possible rating) / PAN Carcinogen rating - not likely (lowest possible rating) PAN Acute Toxicity rating for Sodium Hypochlorite extremely toxic (highest possible rating) / PAN Carcinogenic rating Unclassifiable

14 Woodridge Lake, fluridone and the Connecticut DEEP In 2005 the WLPOA initiated a successful fluridone treatment. During the process there were questions raised about the safety of fluridone and the State permit issued as a requirement for its application. These concerns were forwarded to the CT DEP Commissioner, Gina McCarthy, who provided the attached letter to our Association explaining the permitting process and the CT DEP position on fluridone. In 2013, Ms. McCarthy was appointed by President Obama to Head the US EPA. Her statements made 10 years ago are equally valid today: The final decision to allow the treatment was based on the evidence submitted of your association s past efforts to address the milfoil without success and the fact that milfoil is an invasive species that can, if left uncontrolled, render a lake of this size unusable to boating and swimming. The decision to issue this permit remains a sound, scientifically credible determination that is protective of both public health and the environment.

15 What is the issue with Fluridone? We are all responsible and concerned with safety. We all want to know if there is a problem with fluridone. We would like to see the data validating any problem so that we, as a community, can make an informed decision on an issue that is affecting our most important physical asset.

16 Summary Approximately half of the plants in our lake are invasive weeds. They are affecting the recreational use and the health of our lake. If we do not address the issue effectively now, future remediation efforts will be more expensive, more impactful to the ecology of the lake and more difficult to achieve. If the invasive weeds are not removed, they can only expand. If you clear an area of the lake of plants by any method, the plants that will most likely regrow will be the most aggressive species in the lake, which in our case are EWM and CLP. Therefore, anything short of a significant first step remediation effort only prepares areas for re-infestation. Expect to see a 90% reduction of invasive weeds in our lake the first year of treatment and we can maintain this low infestation level at a reasonable cost moving forward. The use of the aquatic herbicide fluridone has a long track record. The are no human health concerns with the proper use of this chemical and its environmental impacts are well understood and can be effectively managed.

17 References / Additional Information Cover - Lake map provided by Aquatic Controls Technologies is a cibiobase sonar survey of the plant density in our lake on 10/17/14. Slide 7 Graph identifying changes in lake plant population generated from fall vegetation surveys. 155 data points have been established in our lake and are surveyed each year. 107 of these data points are located in the littoral (plant supporting) regions of our lake. The survey methodology utilizes visual inspection where appropriate, a high resolution depth find, an underwater camera and rake tosses. The data shown on the graph is a representation of the % of plant cover on the littoral zone lake bed that is identified in each survey. Plant cover is quantified in a 0 (no plant cover) to 4 (75-100% plant cover) scale and the predominate plants in the zone are identified. NYC 2014 Drinking Water and Quality Report - Woodridge Lake Swimming Pool Chlorine levels taken on 6/07/15 Pesticide Action Network Database - Additional Information: Excellent risk assessment of fluridone (and others) Woodridge Lake Summary Report prepared by Water Resource Services All available on the WLPOA Web site 2014 (and others) Annual Aquatic Vegetation Surveys prepared by Aquatic Control Technology All available on the WLPOA Web site

18 2005 Connecticut DEP Commissioner Letter to the WLPOA