Loading...
HomeMy WebLinkAboutMechanical Harvester DraftOshkosh Sustainability Advisory Board Miller's Bay Aquatic Plant Management Proposal — Aquatic Plant Harvester 117:7_1 a01111iy�FTVI 1"W *11C Background Native and exotic submerged aquatic plants in Miller's Bay, adjacent to Menominee Park reached nuisance levels in 2007 and required action to restore navigation to Lake Winnebago from the sailboat mooring area and the boat landing located at the south end of the bay. The action taken by the city of Oshkosh was to contract with a aquatic plant firm to apply chemical treatments of three areas totaling 21.31 acres on June 10, 26 and July 30, 2008 at a total cost of $20,577.60. These treatments resulted in the immediate relief to navigation. While the chemical treatment was effective at clearing aquatic plant life, there had not been a thorough study of the bay's plant life, and there remained no management plan for the bay. The chemical treatments of the Miller's Bay were paid for partially by an Aquatic Invasive Species grant from the Department of Natural Resources. Part of the grant required that the city have a plant survey conducted of the bay and a management plan drafted. The aquatic management firm Onterra was contracted to complete the study. Their plant survey found that invasive species were not the main nuisance plants. Instead, they identified native species Coontail as the primary nuisance plant. The Onterra plant survey concluded that the plant life in Miller's Bay is indicative of a disturbed system. This disturbance in Miller's Bay is a result of the following: heavy human usage including heavy boater traffice, and it is completely surrounded by maintained lawn and impervious parking areas which result in urban runoff. Aqautic Plant Management: Mechanical Harvesting vs. Chemical Treatment Onterra's study evaluated the management options for the aquatic plant community. They listed four management options: 1) do nothing 2) dredging 3) chemical treatment 4) mechanical harvest. Options one and two were quickly discounted due to ineffectiveness (option 1) and cost (option 2). The other options were broken down by cost and by other pros and cons. Onterra recommended that 16 acres be maintained for navigation and additional areas be cleared to improve fish habitat and fishing opportunities. To annually maintain 16 acres for navigation, the projected cost was $14,240 using a less expensive herbicide than was used in the 2008. Three annual cuttings with a mechanical harvester would total $8,625. The cost of harvesting includes the cost of labor, maintenance, other expenses and the cost of purchasing the harvester after a possible 50% match through a DNR grant. New harvesters cost approximately $100,000. In July 2009, five used harvesters were available from Aquarius Systems, North Prairie, WI ranging from $13,500 to $25,000. Purchasing a used harvester would significantly reduce the startup costs. Further reducing the costs to the city would be contracting the harvester to nearby communities, groups such as the Winnebago Lakes Council, and individuals. There are currently 9 permit holders for nuisance plant control in the area that may benefit from mechanical harvesting. z Figure 1. Onterra's recommended 16 acre harvest area to facilitate navigation. Mechanical harvesting has many benefits over chemical treatment. A primary benefit is that harvesting can be done as appropriate, if needed at all. For a chemical treatment to be most effective, it needs to be applied early in the Spring, before the city can determine how the season will be or how the plants will grow. A dry and cool Spring will often result in significantly inhibited plant growth. In the Spring / Summer of 2009, no chemical treatment was applied, and yet there was not a plant nuissance issue. The city is currently looking into an early Spring chemical application throughout Millers Bay in 2010. But if Oshkosh experiences another cool or dry Spring, this chemical treatment will be unnecessary and a waste of limited financial resources. Owning a mechanical harvester allows the city to harvest as necessary. According to city staff at the Onterra presentation meeting, cuttings that took place in the past when Oshkosh contracted services were to a depth of about'/ of the depth permissiable to cut. These cuttings were considered adequate for about 10 -14 days. By cutting to the full permissible depth, each cutting may then be adequate for 20 -28 days or longer. There may be many seasons in which only one or even no cuttings are needed, thereby saving the city significantly.. 3 A second advantage of a mechanical harvester is public perception. The chemical application of herbicides directly into Miller's Bay entails chemical professionals wearing hazardous material suites spraying herbicides into the water where thousands of Oshkosh residents fish, boat, and swim. This process creates an image of irrisponsibility and disregard for the environment and of the valuable water resources of our community. As the city continues to move towards sustainability and as the city continues its branding of "Oshkosh on the Water ", it is extremely important that the city promote the healthy and positive public image of sustainable water stewardship. A third advantage of a mechanical harvester is that plants are cut in the water and then removed to be composted, leaving few plants to decay in the water to and the feed algae blooms which can turn the water green and mucky. Leaving the plant cuttings in the water can result in a significant absorbtion of oxygen by the decaying plants, impairing the Oxygen levels necessary for healthy fish populations. Further, the removed plant life may be utilized by the UW Oshkosh biodigester to produce renewable energy resources within our community. The fourth advantage of a mechanical harvester is that it is consistent with municipal language and with what the public supports. In surveys conducted in 2002 that were used as a guide for the development of the city's comprehensive plan, residents identified water quality and protection as most important. The comprehensive plan goals call for the protection and preservation of our water resources, shorelands, and environmentally sensitive areas. The comprehensive plan calls for a local water quality initiative while questioning the use of chemical fertilizers and weed control. 4 Recommendations After weighing the costs and benefits of harvesting vs. chemical treatment, Onterra recommended the purchasing of a harvester as the most effective and appropriate primary aquatic plant management solution. The Oshkosh Sustainability Board supports this recommendation and advises the Parks Board and the Oshkosh Common Council to seek the purchase of an aquatic plant harvester. We further recommend that a comprehensive Millers Bay Aquatic Management plan be developed for the wildlife, fish, and water quality of this distrurbed system. We further recommend that chemical use in 2010, should a harvester not yet be purchased, be limited to an as- needed basis and restricted to isolated areas necessary for effective boating.