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The main source of nutrients in Lake George is sediment, which has accumulated behind the dams since they were constructed over 100 years ago. This sediment resulted from poor upland soil conservation practices that were generally followed prior to 1960.
What kinds of options are there for removing the algae? Is it harmful?
Typically, the first steps taken target the control of the external sources of phosphorus and can include: encouraging the use of phosphorus free fertilizers; improving agricultural practices, reducing urban run-off; and restoring vegetation buffers around waterways.
Lakes are very slow to recover after excessive phosphorus inputs have been eliminated. Furthermore, it’s extremely difficult to achieve recovery of lake conditions without additional in-lake management. This is due to the fact that lake sediments become phosphorus rich and can deliver excessive amounts of phosphorus to the overlying water. When dissolved oxygen levels decrease in the bottom waters of the lake (anaerobic conditions), large amounts of phosphorus trapped in the bottom sediments are released into the overlying water. This process is often called internal nutrient loading or recycling.
Alum is used primarily to control this internal recycling of phosphorus from the sediments of the lake bottom that result in algae. On contact with water, alum forms a fluffy aluminum hydroxide precipitate called floc. Aluminum hydroxide (the principle ingredient in common antacids such as Maalox) binds with phosphorus to form an aluminum phosphate compound. This compound is insoluble in water under most conditions so the phosphorus in it can no longer be used as food by algae organisms. As the floc slowly settles, some phosphorus is removed from the water. The floc also tends to collect suspended particles in the water and carry them down to the bottom, leaving the lake noticeably clearer. On the bottom of the lake the floc forms a layer that acts as a phosphorus barrier by combining with phosphorus as it is released from the sediments.
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For additional information, click here, or check out the following links: Wisconsin Department of Natural ResourcesCenter for Disease Control (CDC)US Environmental Protection AgencyNational Pesticide Information Center Department of Health and Family Services WI West Nile Virus / Dead Bird Hotline: 1-800-433-1610
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Coal-tar and asphalt based sealants are used across the nation to protect and beautify parking lots, roads and driveways. These sealants are used commercially and by homeowners on driveways, playgrounds, and parking lots.
Scientific studies have identified coal-tar sealcoat (CTS) as a major source of polycyclic aromatic hydrocarbon (PAH) contamination in urban areas for large parts of the nation. PAHs are a concern because several are suspected or probable human carcinogens and are also toxic to aquatic life. The research is still ongoing with regard to PAHs and there are no acute or chronic exposure levels in the US at this time.
Other communities are noticing elevated levels of PAHs in their storm water pond sediment and are finding that is it very costly to properly dispose of this contaminated sediment. In River Falls, we have over 90 storm water management ponds that collect sediments prior to water discharging to the river.
Asphalt based sealants are similar to coal tar in their use and application. Asphalt sealants are also cheaper than CTSs; however, their effective life is shorter at 4-6 years as opposed to 8-10 years. The main advantage is that pure asphalt sealants are not carcinogenic.
Due to the significant cost of PAH-contaminated sediment disposal, the use of CTSs could have future financial impacts on the City. We are asking for your cooperation in using asphalt based sealcoat if you choose to sealcoat your driveway or parking lot. If you are hiring a professional, ask which type of sealant they use.
How to drain your pool or spa:• Prior to irrigating or disposing of the water, shut off the chlorination system (if you have one) or stop adding chlorine.• Let the water in the pool or spa “sit” for at least one week to reduce the chlorine or bromine level until it is undetectable and temperature is at air temperature. Discharging chlorinated pool/spa water into streams in harmful to fish and other aquatic life.• Measure the pH. It should fall within a range of 6.5-8.5 prior to discharge. Discharge water should not be cloudy or discolored as this typically indicates a pH imbalance.• As the water is discharging, it must be monitored to ensure that it does not cause any erosion or flooding. Erosion is most likely to occur at houses on a bluff that discharge to the rear yard down the steep slope.• Discharges may not run onto a neighbor’s property or across a sidewalk• If a pool or spa has been acid washed, the water may not be discharged off the pool/spa owner’s property.• Water from backflushing pool filters should not be discharged to a stream, ditch or storm sewer. Backflush from pool filters must be discharged to the sanitary sewer or on-site septic tank and drain field system.
Check out our information sheet to find out about different types of storm water management features that the City utilizes to improve the effects of storm water.