Subject: Drainage at Middlesex Beach
To: Joe Reardon, President, MBA Board of Directors
From: Carl Swanson, Chairman, MBA Drainage Committee
February 9, 2001
My wife and I purchased our home at Middlesex Beach in 1965, being among the first few to have a cottage on the pine side. Many changes have occurred since then, but poor drainage is a situation that has prevailed. At the first MBA meeting I attended I asked about the poor drainage and was told that nothing could or would be done about it. Nevertheless, I have tried to assess the conditions that cause poor drainage, with the belief that things could be improved. Others also have studied the situation. I have collected some information through the years and, since early 1966, have tried to act as a point of contact for drainage questions by serving on the Drainage Committee.
Although there are some local drainage problems that occur on the ocean side of Middlesex between Highway 1 and Beach Plum Road, especially after a heavy rain, there is generally no standing water and consequently I will address my comments to the portion of Middlesex Beach west of Beach Plum Road.
The section of Middlesex Beach west of Beach Plum Road is about 5 feet above sea level, with a very sligh slope from east to west. The water table is never more than a few feet below the surface. During a rain, water seeps into the sandy soil and raises the water table, which can reach the surface during heavy storms. In general, unless there is an impervious layer under it, standing water – at the surface, in our ditches, or in the Sea Colony lagoons – indicates the height of the water table. Water flows through the soil very slowly (which allows the water table to be lowered locally by pumping). Ditches are used to drain flat land by providing both a means for surface runoff during and after a storm and a means of lowering the water table. (Areas of Sussex County farmland would be unusable without a network of ditches. Some of these ditches are dug and maintained by special tax assessments and are known as “tax ditches.”)
The United States Geological Survey map for the Bethany Beach, DE quadrangle, dated 1954, shows the drainage in the area before Middlesex was developed. At the time of this map roads did not exist in Middlesex Beach. A drainage channel, probably a combination of a stream and an old ditch, is shows running southwest from the area east of Route 361 (Kent Avenue, then called Muddy Neck Road), crossing the road twice as the road curves, through the area known as Cat Hill, and into the Assawoman Canal about 200 feet south of Jefferson Bridge. The channel is also clearly evident in a 1973 aerial photograph of the area when Middlesex and Sough Bethany, but not Cat Hill, were more developed.
Ditches along the roads in Middlesex were probably dug at the time the roads were made (late 1950’s or early 1960’s). Ideally, ditches along our roads would have a uniform grade from Beach Plum Road to Rte. 361 or Pine Road, but the grading of these ditches was either poorly designed or executed. In general, the ditch on one side of a road is shallower than that on the other side. In addition to the ditches along the roads, a number of ditches run through various properties. Culverts for driveways to individual properties were installed as houses were built. Some lots at the east end of streets do not have or need culverts.
A survey of elevations for the Middlesex ditches was made in 1992 by the (then) United States Department of Agriculture Soil Conservation Service. Although this work was at the request of someone from Middlesex, I don’t know who was involved. This survey, given by engineering sketches, provides information that I have used.
The ditches for Short, Bayberry and Errett Roads all drain towards a ditch on the east side of Rt. 361. The ditch on the north side of Short Road intercepts the old drainage channel. The Rt. 361 ditch is on the right-of-way for the state-maintained street and drains towards the culvert crossing between Short and Bayberry Roads, which is part of the original drainage channel. Reportedly another small diameter pipe crosses between Errett and Bayberry Roads.
The ditches for Bridge Road drain toward a culvert crossing under Pine Road and the entrance to the tennis courts. The ditch on the north side does not run to the end of the street, but crosses under the road at the beginning of the power substation.
The ditches for Addy and Evergreen Roads all drain toward a ditch on the west side of Pine Road. The ditch on the north side of Addy Road runs through a culvert directly into the Pine Road ditch. The ditch on the south side of Addy Road turns the corner and continues along the east side of Pine Road to meet the Evergreen Road ditch. The Evergreen Road ditch runs under Pine Road through a culvert to the west side of Pine Road. From the Pine Road ditch, another ditch runs westward through South Bethany property to meet a ditch that runs through the Cat Hill Development (described in the following section). The west end of the culvert on the north side of Addy Road is the lowest elevation in Middlesex Beach. If free flow existed from this point to the Assawoman Canal, water would rise and fall with tidal and storm variations in the canal.
The drainage away from Middlesex Beach as described in the General Background section has been adversely altered by several construction projects in the area.
Because sections of the original drainage channel between the two road crossings has been filled in by the construction of Sea Colony West and a second power substation on the west side of Rt. 361, the drainage from the northern half of the area relies on the ditches along Kent Ave. The Delaware Department of Transportation (DelDOT), South District Maintenance Section, made a survey of these ditches in 1997 before they cleaned them (at our request). The survey shows that culverts along the road are at a higher elevation than those crossing Rt. 361.
The ditch beyond the second crossing under Rt. 361, which affects the drainage from all of Middlesex Beach, has been altered by the development of the Cat Hill area of South Bethany. A development drawing shows a complete relocation of the old drainage channel to the Assawoman Canal was planned, but only a portion of this plan was carried out. From Rt. 361, the channel was relocated several feet eastward to the property line between Cat Hill and the tennis courts. Apparently at this time a drop basin was installed at the south end of the culvert under Rt. 361. This drop basin does not appear to be connected to the relocated channel, with the outlet being a culvert extending to the ditch along the south side of the road. This culvert, however, is at a higher elevation than the culvert under the road. Drainage from the north half of Middlesex has to flow in the ditches along Rt. 361 toward the canal, but is impeded by poorly placed culverts. The ditch on the south side of Rt. 361 drains into the marshy area between Cat Hill and the canal and eventually into the canal. The ditch on the north side crosses under the road near this location.
The relocated Cat Hill channel begins at a ditch that runs along Rt. 361 next to the tennis courts (an extension of the Bridge Road ditch), runs along the back of six lots, intercepting the ditch from the west side of Pine Road, and then turns toward Periwinkle Road. It crosses under the road and continues toward and crosses under Black Gum Drive. It then runs in the old channel behind the lots on Black Gum Drive to the canal. Although the culverts under Periwinkle Road and Black Gum Drive are of large diameter, water normally stands within several inches of the top.
Several projects are necessary to improve the flow of storm water away from Middlesex Beach. Unfortunately, we must rely on other organizations to carry out this work.
1) Improve the ditches along Rt. 361 from the crossing between Short Road and Bayberry Roads to the crossing near Cat Hill. This work would be done by DelDOT. The work would involve lowering the Sea Colony West and power substaton culverts and providing a uniform grade along the ditch. A new culvert under Rt. 361 at Errett Road could provide additional drainage.
2) Relocate the culvert under Rt. 361 near Cat Hill or construct a connection from the existing drop basin to the ditch between the tennis courts and Cat Hill. This work would also be done by DelDOT.
3) Dredge out the drainage channel through Cat Hill from east of Periwinkle Road to the Assawoman Canal. This work would have to be done by the Town of South Bethany and/or the Delaware Department of Natural Resources and Environmental Conservation (DNREC). Drainage may possibly be improved by a clean-up of the outlet at the canal with the proposed dredging of the canal by the U.S. Army Corps of Engineers.
4) As an alternative to recommendations 2 and 3, improve the ditches along Rt. 361 by grading the ditches and lowering culverts so that water can flow unimpeded to the Assawoman Canal. This work could be done by DelDOT, and may involve DNREC. The work would involve lowering culverts and providing a consistent grading along the ditches. An additional or larger culvert under Rt. 361 near the canal may be required.
Even if the drainage from Middlesex is not improved, we can improve the appearance of the community and reduce the amount of standing water in the ditches.
5) Establish a uniform grade for all the ditches within Middlesex Beach from Beach Plum Road to the end of Middlesex rights-of-way. This work would include some minor ditching, filling in of ditches at appropriate locations and raising and lowering of some culverts on individual driveways. Also included should be the replacement of the culvert under Bridge Road and the tennis court entrance at the south end of Bridge Road. This work could be done over several years under a long term plan.