- Published on Wednesday, 19 March 2014 21:54
- Written by Super User
Pictured above: The Carolina Beach Lake overflowed in 2010 into surrounding areas following an intense rainstorm. The Town of Carolina Beach is requesting permission from the U.S. Army to place dredge material from the lake on an abandoned area at the wastewater treatment plant.
By WILLARD KILLOUGH III
CAROLINA BEACH - The Town of Carolina Beach is seeking regulatory guidance from state and federal agencies for a proposed project to dredge the Carolina Beach Lake on Lake Park Blvd.
Over the years the lake has served as a drainage basin for rain runoff from surrounding acres and during intense storms can overflow flooding area streets and properties.
The proposal calls for removing sediment from the lake bottom and placing it in a basin.
According to a document finalized last week titled, "Carolina Beach Lake Maintenance Project, Scoping meeting project narrative" it states, "The Town of Carolina Beach is seeking guidance, from the regulatory agencies, on federal and state permits that may be required to perform maintenance, dredging/excavation operations in Carolina Beach Lake. The purpose of the proposed maintenance work is to increase the storage capacity of the lake, which is necessary for the following reasons."
Those reasons included:
1. An increased depth will provide greater storage capacity of the lake and improve infiltration rates, which is necessary for flood control and prevention of the main thoroughfare (US421) and residential and commercial structures surrounding the lake;
2. The increased water depth will allow the Town of Carolina Beach flexibility in the amount of pumping they can do without thoroughly dewatering the feature; and
3. The removal of sediment is anticipated to enhance the physical, biological, and chemical functions of the feature.
According to the narrative, "Carolina Beach Lake is an old salt marsh/lagoon that encompasses approximately 11.5 acres. The feature became an isolated surface water body long before the area was developed. Today the lake is surrounded by development (i.e., commercial and residential building, walking path, roadways, and infrastructure). The impoundment serves several functions. First, it is an amenities feature for the residents and visitors of the island. Second, the lake provides some flood control for the surrounding area. And lastly, the feature traps sediments and pollutants, which are carried by stormwater swales and pipes to the lake, before they can discharge into the ocean or Carolina Beach Harbor."
According to the Town, the depth of water in the lake is approximately 18". Based on the features position in the landscape, the formation of the feature and visual inspection, during periods when the lake has been drained, the substrate appears to be comprised of fine silt and organic material. As a result of a stormwater discharge pipe, located on the eastern side of the lake, a sediment plume has formed, allowing hydrophytic vegetation to emerge.
According to the narrative, "Soil & Environmental Consultants, PA (S&EC), in coordination with the Town of Carolina Beach, the NC Department of Natural Resources (DENR) and the US Army Corps of Engineers (USACE) developed a sediment sampling program that would provide data on the presence of RCRA (Resource Conservation and Recovery Act) metals and semi-volatile organic compounds. According
to the report, the sampled sediment did contain concentrations of several of the RCRA metals, but the concentrations were ruled as naturally occurring and not indicative of gross contamination. One compound was detected in the semi-volatilcs analysis (bis-phthalate), but was found to be well below the regulatory maximum for that compound. Shallow soil borings, on the north and south side of the lake, produced an apparent water table of approximately 2 feet below the land surface."
According to the Town the lake is a jurisdictional feature, regulated by the US Army Corps of Engineers (U SACE) under Section 404 of the Clean Water Act and Division of Water Resources (DWR). A jurisdictional determination has not been issued for the site.
The lake is classified as SC waters and is mostly located in an AEI2 flood zone. The classification SC is defined as all tidal salt waters protected for secondary recreation such as fishing, boating, and other activities involving minimal skin contact; fish and noncommercial shellfish consumption; aquatic life propagation and survival; and wildlife.
The narrative states, "According to records obtained from the Town of Carolina Beach, the Division of Coastal Management has determined that the feature is not tidally influenced. Over the years, the lake has become full of sediment and other solids. In an effort to reduce flooding of the lake, the town has created additional stormwater detention ponds, swept the roads regularly, and maintain stormwater pipes and swales. In addition, the town drains the lake, in advance of anticipated heavy rain events, but even this is proving to be not enough, as the lake has very little storage capacity."
In September of 2010, the area experienced extremely heavy rains that were not associated with any tropical storm or hurricane.
The lake overflowed its banks. This caused the closure of US421, the main arterial road through the beach community, and flooded numerous homes and businesses in the surrounding area.
The lake receives stormwater from a 252-acre area.
According to the Town, "At this time, the town estimates 6 to 10 feet of sediment will need to be removed from the bottom of the lake. The work is not anticipated to take place within any high velocity flood (VE) zone and excavation is not anticipated to take place within 5 foot of the normal water level. Temporary impacts to 404 wetlands, located along the water's edge, may be necessary to gain access or perform work. Several options, for accomplishing the desired goal, have been discussed."
Those options include:
1. Dredge material and dispose of spoil to an area within the lake.
2. Dredge and dispose a "slurry" sediment to an old equalization basin at the waste water treatment plant off Dow Road.
3. Remove and dispose a "cake" sediment to an old equalization basin.
4. Pump the dredged material to an old equalization basin.
According to the Town, "The spoil is anticipated to be transported or pumped to the equalization basin, which is on property owned by the Military Ocean Terminal at Sunny Point and located approximately one mile from the lake."
The purpose for the scoping meeting is to discuss the logistics of the project, obtain regulatory guidance on the environmental constraints of the work, and establish any permitting that may be required.
Public Works Director Brian Stanberry explained Tuesday March 18th the Town had meetings with various agencies several years ago and they hope to return to discuss the best approach to accomplish the project based on guidance from those agencies.
Stanberry said the driving factor is flood prevention and four or five years ago the various agencies had differing issues about how to permit the project. He said the Town wants to bring everyone back up to speed and seek their guidance before moving forward with costly engineering planning in order to streamline the permitting process.
Stanberry said timing is also an issue. The project would have to take into consideration the tourism season and nearby Carolina Beach Elementary School depending on whether the sediment was hauled by truck or pumped via a pipeline across the Island to the EQ basin at the treatment plant off Dow Road.
Stanberry said the Town previously obtained preliminary approval from the U.S. Army Military Ocean Terminal at Sunny Point to use the EQ basin to hold the sediment.
He said at this point a projected start date for the project couldn’t be estimated until they gather more information and guidance from the state and federal permitting agencies.
The Town leased land from the Army in the 1970's to build a wastewater treatment plant off Dow Road in the Army's "buffer zone." The "buffer zone" is land taken by the military in the 1950’s for the Military Ocean Terminal at Sunny Point (MOTSU) across the Cape Fear River in Brunswick County. The port is the largest of it’s kind in the world dealing in storage and transportation of explosive munitions. The buffer zone serves as a "blast zone" in the event of an incident. That zone covers the largest area of land west of Dow Road in Carolina Beach, Kure Beach and Fort Fisher.
The Town is proposing to dredge the lake and pump the spoil material, via 3,500 linear feet of pipeline or use trucks to haul it, to the abandoned equalization basin that is located in the southwest portion of the Waste Water Treatment Plant site, on U.S. Army property.
An equalization basin is a pond used for storing wastewater when plant inflow exceeds treatment capacity during peak times.
The abandoned portion of the basin can contain approximately 40,055 cubic yards of material. The estimated volume of material to be removed from Carolina Beach Lake is 37,015 cubic yards, which should fill the void within the abandoned basin. Once the
material has had the proper time to dry, it would then be covered with spoil material from the Wilmington Beach Ponds that is currently present onsite. The Town of Carolina Beach is proposing this as a
solution to the restoration of the EQ Basin, as well as a viable method of disposing of the spoil from the Lake Dredging Project."
In the budget for fiscal year 2012-2013, the budget stated the, "Town is exploring the feasibility, permitting and cost of a project to remove sediment from the Lake, stabilize the shoreline and add additional pumping capacity. The estimated cost of this project is $1,750,000 to $2 million." The budget listed potential debt service at $225,000 a year over ten years.
The Carolina Beach Lake has historically flooded during intense periods of rainfall and hurricanes when storm surge can cause the marina to rise adding water through area drainage pipes connecting the lake to the municipal marina on Canal Drive.
The Town has a pump station located at the lake used to lower the level in anticipation of a storm. That water is pumped to an old ditch that leads to the Cape Fear River west of the Island. When the lake floods, area sewer lines back up and water can be seen coming up from manhole covers.