Details about ‘oxbows’ included in package
On Friday, Sept. 25, Sarasota County staff officially released a solicitation for bids for what Stormwater Department Director Ben Quartermaine has characterized as the Maximum Allowable Dredge (MAD) of Phillippi Creek, The Sarasota News Leader has learned.
The summary explains that the project consists of dredging approximately 77,160 CY [cubic yards] over an estimated 33,500 [linear feet].” The dredging has been planned “to restore the permitted design elevation” of 4 feet mean low water (MLW) between U.S. 41 and South Beneva Road.”
During the County Commission’s regular meeting on March 3, Quartermaine said that the initiative effectively would restore the creek to its status of the early 2000s by “removing 25 years of sediment.”
The submission deadline is 2:30 p.m. on Oct. 28, the solicitation points out.
Quartermaine reported to the County Commission on Aug. 25 that staff intended to issue the advertisement for bids “in mid-September and award the project by the end of the year.”
He also has explained that staff and a consultant have had extensive discussions with the representatives of the U.S. Army Corps of Engineers (USACE) regarding the scope of the undertaking.
A section of the solicitation package notes that county staff permit applications are under regulatory review.
Further the package includes a copy of a June 30 letter from county staff to Toby Schwetje, program administrator of the South District of the Florida Department of Environmental Protection (FDEP), which is headquartered in Fort Myers.
In that, staff explained that it would like to “expand the previously approved dredging activities to include the submerged bottom of the creek within a 10-foot offset from the existing shoreline and adjacent structures to improve drainage and reduce flooding within this portion of Sarasota County. The originally approved scope (i.e., Phase I) targeted isolated high spot areas throughout the creek; this additional scope would include the gaps and previously untouched segments to provide a more continuous and efficient creek channel for stormwater conveyance and adequate drainage capacity. All proposed dredging will occur east of the US-41 bridge.”
The letter added, “The County also seeks authorization to maintenance dredge three oxbow areas located along the creek at Mineola Drive, Seclusion Drive, and River Ridge Drive. Each oxbow was dredged from the uplands prior to 1970 … and is proposed to be returned to historically authorized design width and elevations to match the rest of the creek and restore conveyance capacity and improve hydraulic connectivity within the system. Dredging at each oxbow is proposed as follows,” the letter pointed out:
- Mineola Drive oxbow — approximately 6,031 cubic yards of material to a depth of 4 feet at the Mean Low Water level (MLW).
- Seclusion Drive oxbow — approximately 7,933 cubic yards of material to a depth of 4feet at the MLW level.
- River Ridge Drive oxbow — approximately 16,918 cubic yards of material to a depth of 4 feet at MLW.
“Lastly,” the letter said, “numerous emergent shoals have established themselves along the creek shorelines waterward of existing seawalls since the original channelization. This County would like to remove the accumulated sediment from an emergent shoal located near 2337 River Ridge Drive to restore adequate creek width for vessel traffic and adequate drainage.” It pointed out, “The plat book depicts a creek width of 150 [linear feet] from seawall to shoreline of the platted properties. Removing this emergent shoal would involve maintenance dredging approximately 5,477 CY of material.”
“In total,” the letter noted, “approximately 77,160 CY of material will be dredged from Phillippi Creek.”
The background
The letter also provided details about the creek itself: “Phillippi Creek is a significant waterbody within Sarasota County, bordered by hundreds of residential properties and serving as an important recreational and drainage resource for the surrounding community. The creek supports a variety of recreational uses including fishing, kayaking, canoeing, and boating, while also functioning as a critical conveyance system for stormwater runoff throughout the watershed. Historically, Phillippi Creek was channelized in the 1920’s and has since [undergone] dredging efforts in the late 1990s and early 2000s to restore navigable depths and improve hydraulic capacity.”
The letter then explained, “Over time, natural processes including sedimentation, shoreline erosion, and stormwater transport have resulted in the gradual accumulation of material within the creek bottom. These processes have reduced channel depths in several areas and limit the overall hydraulic efficiency of the system. As sediment continues to accumulate, portions of the creek have become increasingly shallow, creating restrictions to water movement and reducing the effectiveness of the creek as a drainage conveyance during significant storm events.”
Further, the letter said, “Recent bathymetric surveying of Phillippi Creek identified numerous shallow areas and bottlenecks throughout the system. These findings suggest that existing sediment accumulation is restricting drainage capacity and impeding water flow, potentially contributing to upstream flooding. Permitted dredging activities have previously targeted priority shoaling areas within the creek; however, those efforts did not comprehensively address the issue. The proposed maintenance dredging activities herein are intended to restore capacity, enhance drainage effectiveness, and reduce flood risk to adjacent residential communities and public infrastructure.”
Recently, the letter continued, the West Coast Inland Navigation District (WCIND), which is headquartered in Venice, secured permits from the U.S. Army Corps of Engineers (USACE) and FDEP to allow maintenance dredging of “the existing navigational channel within Phillippi Creek to a depth of [4 feet at] mean low water (MLW).” Further, the letter said, county staff obtained additional permits for “maintenance dredging of the creek from bank to bank” upstream of the area where a WCIND contractor undertook its work. An extra “shoal area was approved under a USACE and FDEP exemption verification,” the letter noted.
“All construction activities will be completed from a shallow draft barge, with specific methodology determined by the selected contractor,” the letter added.