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Home My WebLink About2009 08 24 Informational 101 Update on Lake Treatment Program at Oak Forest Lake,.~ COMMISSION AGENDA ITEM 101 August 24, 2009 Meeting CONSENT INFORMATIONAL X PUBLIC HEARING REGULAR MG /DEPT ~/' !~ uthorization REQUEST: The Public Works Department / Stormwater Division is providing the City Commission an update on the Lake Treatment Program implemented at Oak Forest Lake over the past three years PURPOSE: The purpose of this agenda item is to provide the City Commission an update on the lake treatment program implemented at Oak Forest Lake over the past three years OAK FOREST TREATMENT PROGRAM PHASE I - SPATTERDOCK REMOVAL: 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. 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. After meeting with the surrounding residents in 2006 to discuss lake treatment options, the lake was treated several times with an herbicide called "Sonar." 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. The surrounding residents were highly cooperative with the Sonar treatment program and they complied with the temporary irrigation restriction during the treatment period. • The photo on the following page is from October 2006 in the pre-treatment conditions, followed by a photo of the post-treatment conditions in February, 2007. The Sonar treatment program substantially eliminated the spatterdock. • After the Sonar treatment was complete, Staff met at the lake with Amy Giannotti, a scientist from the Fish and Wildlife Conservation Commission -Invasive Plant Management Section. Ms. Giannotti observed the lake and confirmed the success of the Sonar treatment but she also noted that in several years we may see the spatterdock start to return. Informational Agenda Item #101 August 24, 2009 Page 2 of 7 • In July 2009 it was observed that the spatterdock had indeed started to return to the lake, although not nearly to the extent of coverage in 2006. Staff is planning to implement another round of Sonar treatments in October 2009 to address the problem before it becomes unsightly. October 16, 2006 -Pre-treatment Condition .r. _. y w:., ~, ~: 2007 -Post-treatment Condition -~~.,:, August 17, 2009 -Current Condition Informational Agenda Item #101 August 24, 2009 Page 3 of 7 OAK FOREST TREATMENT PROGRAM PHASE II -LITTORAL ZONE PLANTINGS The second phase of the Oak Forest Lake treatment program was implemented in April 2007 and consisted of the installation of littoral zone plantings along the uninhabited shoreline areas along the lake's east side. 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. The goal for the littoral zone is to utilize a mixture of native aquatic plantings that will benefit the lake's ecosystem, look attractive, and be relatively easy to manage. The photo below shows a portion of the littoral zone plantings after installation. Unfortunately, the littoral planting zone did not flourish as planned primarily due to the presence of weed eating Triploid Grass Carp in the lake. The City stocks some lakes and ponds with Triploid Grass Carp as an effective non-chemical means to help control invasive weeds. At Oak Forest Lake, the Grass Carp ate all but a small percentage of the aquatic plantings. Oak Forest Lake has an abundant Grass Carp population and with almost no other vegetation available within the lake the Grass Carp quickly consumed the new plantings. NEXT STEPS: At this time the spatterdock problem is being effectively managed with periodic Sonar treatments; however, the overall lake water quality remains a concern. Staff is exploring several options to address the lake water quality over the long-term, including the following: o Re-planting at least a portion of the littoral zone plantings, along with the installation of a temporary barrier that would prevent the Grass Carp from having access to the plants while they are in early development. The mix of plant species may also need to be changed. Informational Agenda Item #101 August 24, 2009 Page 4 of 7 o Installation of floating plant mats at one or more locations. Floating plant mats (Beemats) provide the benefits of vegetated littoral shelves without having to deal with the problems associated with changing water levels, and they are less vulnerable to fish consumption. Floating plant mats use interlocking mats, combined with aquatic plants in perforated pots, to suspend a simulated shallow water environment. This not only takes care of fluctuating water levels, but also produces oxygen, takes nutrients and pesticides out of the water, and provides habitat for wildlife utilization. The floating plant mat consists of puzzle cut mats held together by nylon connectors. The mats may be assembled in any size or shape. After the mats are connected, plants are inserted into pre-cut holes. The plants may be any species of emergent aquatics. The mats can be attached to anchors or shoreline stakes. Below is a photo of a floating plant mat at Lake Eola in downtown Orlando. o Installation of Bioretention filters at stormwater inlets surrounding the lake. Bioretention filters are stormwater treatment structures located immediately upstream and adjacent to the existing curb inlets. Stormwater runoff drains directly from the street through an inlet filtration structure in a concrete box and flows through filter media consisting of mulch, plants, and soil. Treated water flows out of the system via an under-drain connected to the adjacent curb inlet (see diagram below). The main benefit of Bioretention filters is that they treat runoff and remove pollutants before they reach a water body. Informational Agenda Item #101 August 24, 2009 Page 5 of 7 Bioretention Filter Schematic by Filterra .~era~rr:: rk~ i.~~ ~ ', t r~ ;.~,.,r. Tur hvw l I~~.Fo ~ -e'~. ~ ., fey cod-~ ~~'~ r. ~ ~~ *~; Bioretention Filter o Install Floc-Logs at various lake inflow locations. Floc-Logs by Applied Polymer Systems, Inc. are blocks made of asemi-hydrated polycrylamide blend that when placed within turbid water flows will remove fine particles and reduce turbidity. Floc-Logs can be placed directly in stormwater pipes or in storm structures. Floc- Logs have recently been installed on a trial basis by Seminole County at a pond in Central Winds Park and there has been a noticeable improvement in pond water quality. ~{IINNININNNI ElroalSmlMr.rnb«f.nryN«^ F•mowa PathllmN~. ESS. NrwaCasliag Cab and Calch aasML flr/ Cq CdlHa/ a~d~'a'aq Cha'IaN Iblwl EflACpixrtaua Nira;plp fkAry AAHaIa N/dn~}cwhwli,N: /1 ~ M.~i~lluw Hgltw Ei~wUw~ ~~w~. Nyoaas itaw t.ie :~! `', FIaU~A' C i ror Vorm Mean hll«w 1'Eust Flueh") ~ ! NaaoYrxylPa}In~tq II - ~ 1^ Te ~..N.d Stanwetn ~~ ~~ V ~~~q thwM~eran sy,t.m AGmrµ Idw W SIWSa`WT kYluat Informational Agenda Item #101 August 24, 2009 Page 6 of 7 Central Winds Park Pond After Floc-Log Installation STORMWATER POND MANAGEMENT PROGRAM SUMMARY: The City's Stormwater Management Program includes the management and maintenance of approximately 100 lakes and ponds throughout the City. The City contracts the aquatic weed control and maintenance of these lakes and ponds. The aquatic contract calls for the lakes and ponds to be inspected and maintained a minimum of once per month, with higher frequencies at ponds needing more attention. The aquatic management and maintenance is achieved through both chemical (herbicides) and biological (fish stocking) applications. ,~ Informational Agenda Item #101 August 24, 2009 Page 7 of 7 During the last two years the City has also implemented both aquatic and tree planting programs for city-maintained lakes and ponds. Over the past two years the City has planted an estimated 25,000 aquatic plants of various species and 500 trees of various species (see photos below). • The City continues the implementation of biological treatments with fish stocking to reduce the dependence on herbicide applications. The City currently has 22 lakes and ponds stocked with weed eating Triploid Grass Carp. Before stocking a pond with Grass Carp a permit is required from the Fish and Wildlife Commission. The City has stocked these 22 lakes and ponds with an estimated 780 Grass Carp over the past 10 years. FUNDING: None RECOMMENDATION: N/A ATTACHMENTS: None COMMISSION ACTION: S.R. 434 Pond near Post Office Shepard Road Pond near Edgemon Ave