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Credit: David Kincaid, Devo Engineering

After the 2004 hurricane season, water levels around Lake Sherwood in Orange County were extremely high.
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Credit: David Kincaid, Devo Engineering

After exploring several alternatives, the Orange County Roads and Drainage division elected to replace one drainage well near Lake Sherwood with four wells 2500 southeast of the existing well.

On Sept. 4, 2004, Hurricane Frances struck Florida with high-velocity winds and heavy rainfall, just three weeks after Hurricane Charley. Some areas of Florida received more than 13 inches of rain during the storm's slow passing. Lakes and ponds overfilled, and many roads and residential areas flooded. The area around Orange County's Lake Sherwood was flooded during Hurricane Frances. High water levels created water damage to residential properties and septic systems.

This flooding was similar to October 1960, when Hurricane Donna flooded homes on the lake's north side; the landlocked lake had had no outfall to alleviate the flooding. After this hurricane, crews installed a 24-inch diameter drainwell to the lake's west side to discharge water to the Floridan aquifer. However, after 44 years, the drainwell could not handle the heavy rainfall due to deterioration. Even though replacement of Lake Sherwood drainage well was already in the works, the flooding caused by Hurricane Frances served as a reminder of how urgently a replacement well was needed.

Since 1999, the Roads and Drainage (R&D) Division of the Orange County Public Works Department has contracted consultants to assess the well condition and perform drainage evaluations of the Lake Sherwood basin. For instance, during an October 2000 video assessment of the drainwell, Orlando-based contractor Henderson Wilder discovered holes in the highly corroded casing that were allowing sand entry into the aquifer. In addition, significant erosion near the well was exposing the intake pipe.

Initial consideration was given to rehabilitate the drainwell, but there was a potential for well failure due to extreme deterioration. A collapsing well could cause significant property damage, including to an existing wastewater force main located 10 feet away. The well needed to be replaced.

A NEW PLAN

In October 2003, the R&D Division contracted with Orlando-based Professional Engineering Consultants Inc. and Orlando-based Devo Engineering to design and prepare construction specifications for the drainage well replacement. The consultant recommended constructing four drainage wells to replace the existing one.

Evaluation of the drainwell site showed it was not appropriate to construct the new wells at the same location as the existing one. The existing well was located a few feet away from the north side of State Road 50. This location was difficult and dangerous for county staff to maintain due to access restrictions. Additionally, future road expansion would have placed the wells even closer to the roadway.

All properties around Lake Sherwood were evaluated as potential locations for the replacement wells. An initial location was selected to the east side of an existing county-owned wastewater lift station. This property was located to the northwest side of the existing drainwell. Though approved by the Florida Department of Environmental Protection (FDEP), the location had to be changed due to access problems and the need to purchase additional area; the process for easement acquisition at this location would have posed a time constraint.

A suitable location was found approximately 2500 feet southeast of the existing well, within county-owned property. In order to satisfy FDEP requirements for approval of the site, the county needed to perform an inventory of wells within 1 mile of the proposed drainage wells. The objective of the inventory was to assess the potential impact of the new drainwells on nearby potable water wells. The initial inventory identified about 36 wells, with the closest well approximately 1100 feet from the proposed location. A second inventory identified more than 100 wells within a 1-mile radius of an alternate location.

The FDEP requested that the county perform water quality sampling to these wells to get conditional approval for the Lake Sherwood drainage well replacement. While waiting for the implementation of the monitoring plan, Hurricane Frances flooded several houses near the lake. The FDEP issued an emergency ordinance in September 2004, allowing the R&D Division to replace the existing drainage well with four drainage wells at the new location. Finally, three months later, the FDEP granted approval for the replacement wells provided that the county assumed responsibility for any adverse impact caused by the new wells.