919918 Public Notice - City of Alexandria Environmental Summary
Publish June 5, 2009
CITY OF ALEXANDRIA
MAY 18, 2009
Project Name: Water Treatment Plant Rehabilitation and Filter Addition
Project Number: 1210001-3
Legal Description: NW 1/4, Section 17, Township 128N, Range 37W, Douglas County
Project Proposer: City of Alexandria, Alexandria Light and Power, P.O. Box 609, Alexandria, MN 56308
Present Water System and Need:
Alexandria’s current water treatment system consists of a central iron and manganese removal plant that treats groundwater from an adjacent well-field. The plant currently has a maximum capacity of 2.2 million gallons per day, and produces an average volume of 1.5 million gallons per day. The treatment process consists of filtration, disinfection and fluoridation. At present, the plant cannot meet its current capacity demands due to inadequate over-all filter performance. Process limitations include shortened filter-runs and incomplete backwashing, insufficient settling and contact time prior to filtration, limited capacity to disinfect during peak demands, and insufficient storage volume at the plant.
To address the current capacity challenges and assure that a high-quality drinking water continues to be delivered to its consumers, the city of Alexandria plans to optimize and expand its current filtration process at this time. Backwash and detention systems will be re-designed to promote capacity, enhance performance and reduce future chemical costs. The current filter media will be replaced with a manganese-greensand type to improve filter performance, and the reclaim tank will be structurally modified to promote better settling. Plant capacity will be expanded by constructing three new filter cells at the northwest corner of the existing plant, and adding 200,000 gallons of capacity to its underground storage reservoir.
The primary impacts of the project are short-term construction related disturbances such as noise, dust and erosion. Construction will be limited to the project site and all disturbed vegetative areas will be vegetated back and restored to pre-construction conditions. Standard construction practices and control measures will be implemented to mitigate dust, potential erosion and sedimentation, and to prevent impact to the surrounding area. Such measures include dust suppression, drainage control and temporary cover of topsoil stockpiles. In summary, the proposed project is expected to result in no direct impacts to: threatened or endangered plant or animal species or their habitat, wetlands; flood plains; nearby farmland; historic, architectural, cultural, or archeological features; shore lands; or air quality non-attainment areas.
Public Participation Programs:
Public notification and request for comments regarding the project was published in the Douglas County Echo Press on April 8, 2009. One request was made, and assurances were duly provided, that all movement and storage of heavy equipment in and around the construction area will be limited to city-owned property. Beside this request, no written or oral objections were received during the period of public notification.
/s/ Jon Groethe, P.E.
Public Health Engineer
Section of Drinking Water Protection