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HomeMy WebLinkAbout2007 02 26 Informational 504 Oak Forest Lake Treatment Program COMMISSION AGENDA ITEM 504 INFORMATIONAL February 26, 2007 Meeting MGR.f>J.\ IDEPT /~ Authorization REQUEST: Public Works Department Informing the City Commission on the Oak Forest Lake Treatment Program PURPOSE: The purpose ofthis agenda item is to provide the City Commission with a summary of the completed and planned Oak Forest Lake treatment activities. CONSIDERATIONS: . Spatterdock (also known as yellow water lily) is a rooted aquatic plant with large floating leaves common to lakes and ponds in Florida. Oak Forest Lake experienced a spatterdock bloom in 2006 that became difficult for the City to manage and it was unsightly for the lakefront residents. The photo on the following page is from October 2006 in the pre- treatment conditions, followed by a photo ofthe post-treatment conditions in February, 2007. . On September 12, 2006, the City held a public meeting attended by a majority ofthe lakefront residents, and it was agreed that the spatterdock should be removed. While spatterdock is beneficial to water quality, wildlife habitat, and it can be an important part of a lake ecosystem, it can also be difficult and costly to control its growth. Most lakefront residents felt the spatterdock was unsightly, especially at the extent it was covering the lake in September, 2006. . An herbicide called "Sonar" was chosen as the treatment chemical to eradicate the spatterdock, based on its proven effectiveness with similar applications. Sonar is highly effective at removing spatterdock, but it can also damage lawns and therefore the lake could not be used for irrigation during the treatment period, which was estimated to be 60-90 days. Since many lakefront residents utilize lake water as their only irrigation source, Sonar was not favorably considered in prior years. However, at the September 12 public meeting, the residents agreed with the proposed Sonar treatment plan and they committed to complying with the temporary irrigation restriction during the treatment period. The Sonar application was planned to start in mid-October when it was expected that cooler temperatures would reduce the irrigation demand. PICTURES INFORMATIONAL AGENDA ITEM 504 PAGE 2 OF 3 OCTOBER 16, 2006 PRE TREATMENT CONDITION FEBRUARY 16, 2007 POST TREATMENT CONDITION Informational Agenda Item 504 February 26,2007 Page 3 of 3 . A total of four Sonar treatments were applied to Oak Forest Lake from October to December, 2006. The City purchased the Sonar chemical at a cost of approximately $1,000. The treatments were applied by the Lake Doctors, the City's pond maintenance contractor, at no additional cost to the City. . As the post-treatment photo indicates, the spatterdock has been substantially removed, although some stems can still be seen above the water line. The remaining spatterdock stems should naturally disappear over the next two months without needing any additional chemical treatment. Overall, the spatterdock removal program took about 45 days longer than expected. All indications are that the Sonar treatment has been effective and the spatterdock will not be growing back any time soon. . On February 19, 2007, The City met with Amy Giannotti, a scientist from the FDEP Bureau ofInvasive Plant Management, to visit the lake to review the effectiveness of the Sonar treatment program. Ms. Giannotti observed the lake and confirmed the success of the Sonar treatment. She said the lake should be free from spatterdock for some time. Ms. Giannotti also said it is important to restore aquatic plantings in the lake to provide the nutrient uptake function (stormwater pollutant removal) that was being performed by the spatterdock. . The second phase of the Oak Forest Lake treatment program is the restoration ofthe littoral zone plantings. The littoral zone is an area of aquatic plantings near the shoreline that provides many benefits, including stormwater pollutant removal, bank stabilization, and wildlife habitat. For Oak Forest Lake, it was agreed that the littoral zone would be focused initially along the uninhabited shoreline areas along the lake's east side. The goal for the littoral zone is to utilize a mixture of native aquatic plantings that will benefit the lake's ecosystem, look nice, and be relatively easy to manage. Exhibit 1 shows the location of the littoral zone and several of the aquatic plantings being considered. Staff will be working on the littoral zone restoration over the next several months. ATTACHMENTS: 1. Exhibit 1 - Oak Forest Lake Littoral Zone COMMISSION ACTION: EXHIBIT 1 OAK FOREST LAKE LITTORAL ZONE