|
|
|
LIBERTY LAKE NUTRIENT REDUCTION PROGRAM With increasing development and growth we have changes in water quantity and water quality within a watershed. Changes in water quantity result from alterations in a sites physical environment. This is caused by an increase of the impervious area on the site, a decrease in the vegetative cover, and alterations to the slope. Changes in water quality result from transformations in land use that contribute new or additional pollutants to runoff (EPA, 1992). Together, these are defined as stormwater runoff. As we have more development of rooftops, driveways, streets, and other hard surfaces, runoff increases and drainage patterns change significantly. Because of these changes, it is necessary to provide and enforce stormwater controls and Best Management Practices (BMPs) to reduce stormwater pollution. There are two basic types of pollution, point and non-point source pollution. Point source pollution is defined as pollution coming from a single source, like a pipe. Non-point source pollution, is pollution coming from an accumulation of many different sources with no single identifiable source or specific outlet. Non-point source pollution is the most important source of pollution to control because it is the most difficult to manage and can be the most detrimental to our aquifer, streams, and lake. For instance, in the Liberty Lake area, non point sources include: runoff from roads, residential areas, aquatic animals, and the county park. Point sources include: drainage channels from roads, natural drainages and existing springs, and the marsh. There are many non-point source pollution controls in place in residential areas such as stormwater swales and stormwater barriers (silt fences). A stormwater swale is a depression that collects stormwater runoff from streets, driveways and rooftops. They are designed according to the area of impervious surface, and dispose of stormwater through an infiltration process. Water soaks into the ground through the pore spaces in the soil of the swale and eventually recharges the groundwater (aquifer) (Spokane County Informational Handout). Silt fences are another means of protection from stormwater. Silt fences are constructed from geotech fabric and are designed to prevent sediment from becoming runoff at construction sites where excavation has occurred. Minimizing contaminant sources from both point and non-point sources is positively the best long term solution to protecting the quality of water.
STORMWATER CONTROLS AND BMPs Since the late 1800's, Liberty Lake has experienced a steady population growth within the watershed. Due to this growth, the natural eutrophication process of the lake was being speeded up by human activities. The deterioration resulted in a lake restoration plan to address the need to protect and preserve the water quality of the lake. As part of this restoration plan, the Liberty Lake Sewer District adopted its first ordinance for stormwater management in 1981 (Century West, 1998). This ordinance was updated in 1985, 1987, and 1992. In 1994, the district received a Washington State Centennial Clean Water Grant to develop a stormwater management plan. The district authorized Century West Engineering Corporation to proceed with the preparation of a Comprehensive Stormwater Management Plan in 1996 (Century West, 1998). As part of this Comprehensive Stormwater Management Plan, the district has the authority to provide for the reduction, minimization, and/or elimination of pollutants from lakes, rivers, and groundwater, including those contained in stormwater; pursuant to RCW 57.08.005(8) (Century West, 1998). The comprehensive plan is designed to provide guidance and criteria for establishing and maintaining water quality within the Liberty Lake Sewer District's boundary and the lake's watershed. Focus is placed on:
LLSWD STORMWATER REQUIREMENTS The Stormwater Resolution 21-98 as amended on July 13, 1995, provides the Liberty Sewer and Water District the authority to require a policy for stormwater management within the district boundaries. These policies may include, a Residential Drainage Plan, Stormwater Drainage Plan and Review, and/or a Stormwater Barrier (silt fence). In the event of a Stormwater Drainage Plan, the district has the authority to issue a review and inspection fee of $390 for the plan review and inspection of stormwater swales. The fee covers the initial plan review and a check of the final plan, three site drainage inspections (rough, preliminary-final and final), and stormwater barrier (silt fence) installation. Any additional plan review and inspection will we billed to the homeowner an actual costs per hour. If these best management practices are followed, we can all help preserve the natural watershed and protect the beneficial uses and the quality of water. For information on development near the shoreline, visit our Shoreline Development page Below are some examples of stormwater swales within the Liberty Lake Sewer and Water District.
Click to enlarge the photos For additional information regarding stormwater management practices, please visit the link below. http://www.spokanecounty.org/utilities/
ANNUAL BEACH AND LEAF CLEANUP In November 1992, the LLSWD initiated a fall beach and shoreline clean-up program as an effort to reduce leaching of nutrients from debris entering the lake. Approximately a week is spent in the fall in a cooperative program with property owners to gather leaves and aquatic macrophytes from the immediate watershed, city, and shoreline around the lake. Every fall the residents are asked to gather up their leaves, place them in bags, and set them on the curb. The LLSWD and volunteer citizens then pick up the bags and haul them off to a controlled area to be disposed of. This collective action demonstrates the high value of pollution prevention. In fact, an estimation was made in the fall of 1998 that about 3000 bags each weighing nearly 40 pounds were collected and about 3 tons of wet macrophytes were removed from the wet area of the shoreline. Laboratory digestion and analysis of mixed sub-samples indicated phosphorus content of about 0.11 percent phosphorus dry weight. This would indicate about 56.4 Kg (124 lbs) of phosphorus was prevented from being carried or leached into the lake by precipitation (Liberty Lake Annual Report, 1999).
Beach and Leaf Cleanup Photos
Click to enlarge the photos
|
|
|
