|
September 5, 2001 Mr. Paul Yauk Planning Section Parks and Recreation Bureau Department of Environmental Resources Stevens T. Mason Building P.O. Box 30028 Lansing, MI 48909 |
||
|
||
|
Dear Mr. Yauk: The purpose of this letter is to provide the results of the prudent and feasible alternative study for a Lake Michigan water intake in Allegan County. The report follows: Background Laketown Township and Allegan County (LTAC) first considered the concept of providing water to Allegan County communities in 1998. Many communities within the County continue to have water quality and quantity problems. As a result, LTAC further pursued the potential of providing Lake Michigan water to the county by studying the feasibility of alternative intake locations. Intake Assumptions The recommended intake design includes the following:
Mr. Paul Yauk September 5, 2001 Page 2 Location of Intake and Pumping Station The first step in determining the feasibility of constructing a water system in Allegan County was an analysis of the potential intake locations. Since the water supply is Lake Michigan, this analysis considered locations within Allegan County along the Lake Michigan shoreline. The intake would be located at a depth of approximately 15 feet below the lake bottom. As a result, significant area is needed due to the slopes of the necessary trench for construction. A minimum of 1 acres is recommended for the lift station with a 4 acre construction easement area. All locations south of the Village of Douglas Since many of the primary potential customers are located in northwestern portion of Allegan County, it would not be feasible to locate the intake south of the Village Of Douglas. The southwestern portion of the County is relatively sparsely populated and does not project a significant customer base. Thus, construction of a transmission main to the primary customer base within the County is not cost effective. Initially, the primary customer communities include the Village of Douglas, Village of Fennville, Fillmore Township, Hamilton, Laketown Township, City of Saugatuck, and Saugatuck Township. These are all located in the northwestern portion of the County, as shown in Figure 1. Also, a significant clay bluff is located south of Douglas. This bluff rises to an elevation of 50 to 70 feet above the normal Lake Michigan water level (-580 feet). It would not be feasible to build an intake and raw water transmission main under this bluff. Locations of high bluff line are shown in Figure 1. Village of Douglas, City of Saugatuck, Saugatuck Township While there are less significant bluffs in these locations, this area is a residential center and is located at the discharge of the Kalamazoo River. The purchase of property in this area would be difficult with consideration for the needed easement area for the low lift pump station. Since the low lift pumps are located approximately 30 feet below Lake Michigan, approximately a 4 acre area is needed somewhere near the shore. Also, any location within several miles of a river outlet could be susceptible to some clogging as a result of silt being carried by the river and discharged into Lake Michigan. Mr. Paul Yauk September 5, 2001 Page 3 Clogging could be severe if the outlet is within a mile. However, the Kalamazoo River has less sediment deposit at the Lake Michigan discharge due to settling in Lake Kalamazoo, located nearly 2.5 miles from the shoreline. 140th Avenue north to County Limits Beginning at 140th Avenue, a sandy bluff line exists at an elevation significantly higher than Lake Michigan. In fact, the bluff rises to 180 feet above the average Lake Michigan water level in some locations. There are some breaks in the bluff line; however, severe dune side slopes exist in these locations. In Laketown Township, near the old prison This is an opportune site and is the recommended site. The intake would be located near larger customer service areas. There are no high bluffs. Land is available for the low lift pump station, and the Township already has an easement and land that could be used for the treatment facility. There are two specific sites that have been identified. These are shown on Figure 2. Location 'A' has abundant open space for the low lift pump station and would require minimal disturbance to the bluff. Location 'B' has less space for the intake but would require less easement for the raw water main. Each location is more than 9,000 feet from the Kalamazoo River outlet and should not be susceptible to serious clogging. While some clogging is possible, it will be minimal due to the presence of Lake Kalamazoo near the outlet of the Kalamazoo River. Infiltration Bed An infiltration bed intake is proposed for construction in Lake Michigan. The infiltration bed construction begins with excavation in the bottom of Lake Michigan. Total depth of the excavation is 12 to 15 feet. Slotted pipe surrounded by gravel is placed in the bottom of the bed. The gravel is covered by a sand backfill using native Lake Michigan bottom sand. The capacity of the intake relies upon the infiltration rate of the native lake bottom sand. It is expected that the bed would be constructed approximately 1,000 to 1,200 feet off shore. It would be connected to a pumping station on shore by a larger intake pipe. The depth of the pumping station would be approximately 20 feet below the low water level in Lake Michigan. This will allow the pumps to draw the water level down approximately 15 feet below the Lake Michigan level, thus providing the hydraulic Mr. Paul Yauk September 5, 2001 Page 4 gradient which will allow the intake to operate. The pumps, in turn, will be connected to a transmission main which will deliver the water to the treatment plant. The advantages of this type of intake include high clarity water with very low turbidity. Fish and debris of any sort which may be in Lake Michigan are excluded from the intake. Zebra mussels which have clogged many water intakes do not interfere with the infiltration bed. There are two other infiltration beds in Lake Michigan with a similar design which have occasionally experienced problems with clogging. The intake at Ludington has clogged once in 30 years. The intake at Grand Haven has clogged several times during the past ten years. The cause of the clogging is silt and clay material. The source of the silt and clay is suspected to be the material that deposited in the river and harbor channels which is dredged by the Corps. of Engineers and used for beach nourishment as well as silt carried by the Grand River into Lake Michigan. The recommended intake location will likely have minimal clogging due to the distance to the Kalamazoo River. Two intake beds are proposed so that one can be used for backwashing the other, if necessary. Each bed will be designed for full capacity. The exact location of the infiltration beds is located based on a Lake Michigan bottom survey. Consideration is given to the waves and currents in the lake, lake levels, sandbar locations, ice buildup, bottom soil types, and other related conditions. In general, this type of intake provides a superior quality raw water with relatively low maintenance requirements. Permits Several permits will be necessary for the construction of a water system. We have prepared a summary many that could potentially be needed.
|
||
|
Return to CCSDSP Water Treatment Plant Proposals page.
www.SaugatuckDunes.org |