|
|
|
location Long & Foster Agenda note: Board Meetings are open to Community Members |
|
|
|
DRAINAGE REPORT OF
THE MIDDLESEX BEACH ASSOCIATION PUBLIC WORKS COMMITTEE August 2004 |
|
|
Your Public Works Committee has come up with a minimally-invasive, environmentally-sensitive, cost-efficient, community-responsive, long-range-adaptable drainage plan that it will be putting into effect this coming fall. In keeping with the "Demonstration Plan" process, we will see immediate benefits at an extremely reasonable cost and learn much by replacing/relocating (nearly) all driveway culverts along north side of Addy Road this fall and FOR NOW essentially ignoring the ditches themselves. This plan borrows heavily from several previous drainage studies and recommendations made over the past 30+ years, and seeks to remove standing ditch water via a combination of downhill flow and percolation through the surface.
All existing driveway culverts on this side of Addy Road are 21' in length (concrete). New plastic culvert sections are 20'; we will install approximately 27' (1 1/3 sections) of culvert per driveway. This should reduce the desire for property owners to build elaborate stone walls adjacent their culvert in order to maximize their driveway width. Each culvert will be placed at a level slightly above the culvert to its west (downstream). When each old culvert is dug up, each driveway will be dug out low enough so that the hard pan clay layer that underlies most of Middlesex Beach is fractured. The new culverts will be placed on and surrounded by 2" stone-the seemingly weak plastic culverts derive most of their strength from the stones that surround them and hold them in place. Since most of the material that is dug up to get to the old culverts will be replaced by stone, this extra material will approximate what's needed for top cover on the new longer culverts. Any large amounts of surface water that accumulate in each ditch will be able to drain downhill since the culverts will all be located above the existing drain point for the community. Since the new stone will extend beyond the end of each culvert, it should be possible for the water in that ditch section to either percolate into the adjacent downhill ditch section, or directly into the ground. The end point of this ditch is an existing 60' culvert under Pine Road. The water level at this location has been monitored over the past year. While there are certainly times when the water level at this point is above the top of the culvert and there are times when this location is quite dry, within a day or 2 after any major storm the water level settles at a pretty consistent level, namely about halfway up this 15" diameter culvert. This halfway elevation is our designed lowest point of the new drainage system. The plan will include construction of a catch basin at this location, which will serve multiple purposes. It will be a cleanout point to keep large debris from getting caught in the 60' culvert under Pine Road. It will be located such that its input is at the design elevation in order to keep water from backflowing into the community's ditch system. It will be adaptable to having a baffle installed which, in combination with a pump, will allow us to pump water out of the community and into the Pine Road culvert even if the downstream ditches have a higher water level than we would like INSIDE our community. Any ditch portion which is below this design elevation will be filled in. For the most part, the elevations of the remaining ditch bottoms will be left alone FOR NOW. This means we'll only need to do work on about 20% of the frontage of most of the properties, and can avoid disturbing the rest. This will also result in some culverts which are initially higher than the adjacent ditches. The above "percolation enhancement" will assist in moving the water downhill below actual culverts. Eventually, these lower portions will get filled in themselves, or it could be done later. Miss Utility will of course be requested to make a visit prior to finalizing the plan. Such a plan will be adaptable in the future to include installation of surface drains and burying the remaining system should that prove desirable. 21 and 23 Addy will need a bit of special attention; their ditch is the high point, which is why 25, 27 and 29 Addy frequently flood, even though they're at the high end of the street. Whatever is removed from this portion of the street will be used to fill in other ditch sections as needed. |