Florida
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Renaissance for Lake Jackson -
An Outstanding Florida Water
Lake Jackson in northcentral Leon County, Florida, became known for its
bass fishing in the late 1950s and was held in high esteem until the early
1970s when rapid urbanization of its watershed resulted in dramatic changes to
the lake. The lake is a relatively closed system with no outlets other than
several sinkholes. In fact, its renown followed a natural drawdown after the
collapse of a solution sinkhole.
In addition to the stress of residential and other urban development, a
major federal highway, Interstate I-10, was built through the Megginnis and
Fords Arms subbasins in 1972. Above average rainfall during the highway's
construction, coupled with inadequate sediment controls, created a large
turbidity plume over the southern third of the lake. Subsequent efforts to
protect the lake turned Megginnis and Fords Arms into sediment traps.
A clean lakes remedy
Many studies conducted between 1974 and 1976 indicated widespread problems,
including increased sediment, nutrient loading, and contamination of the bottom
sediments by heavy metals and other pollutants. The Northwest Florida Water
Management District compiled and evaluated this research in a 1977 report. The
report concluded that stormwater runoff was the primary cause of Lake Jackson's
water quality degradation. It recommended that nutrient and sediment loads to
the lake be reduced. In 1981, a partnership was established between the Florida
Department of Environmental Regulation, the Northwest Florida Water Management
District, and EPA. Using a section 314 Clean Lakes program grant, the partners
built a detention pond, sand filter, and marsh system to reduce the flow of
stormwater pollutants through Megginnis Arm.
This system, completed in 1984, was studied extensively for the next four
years and eventually refined for optimal performance. No matter how efficiently
the system operated, it was still undersized in relation to development within
the watershed. Stormwater loadings were substantially reduced, but the lake and
Megginnis Arm continued to deteriorate.
Removing sediment
In 1990, the Florida Department of Environmental Regulation committed section
319 funding to the Northwest Florida Water Management District to remove the
troublesome sediments from Megginnis Arm. Analyses indicated that the sediments
were well within the limits for land application.
The project broke ground October 11, 1990. The first tasks centered on the
establishment of sediment controls and site barricades. Favorable weather and
minimal equipment problems enabled rapid construction of the disposal area and
a sheetpile dam to isolate Megginnis Arm from the main body of Lake
Jackson.
Dredging started on December 3, 1990. Low water levels facilitated progress
until they were too low to support the dredge. Groundwater provided by the city
of Tallahassee was then used to augment the pool.
Concerned that the dredge slurry could not be effectively controlled in the
disposal area, the project used a section of an adjacent constructed marsh as a
polishing pond. To counter unusually heavy rains from January to March 1991,
hay bales were placed between sections of the marsh to protect the main area,
while increased alum treatments helped control turbidity.
Dredging in Megginnis Arm was completed by July 1991, followed by
reconditioning of the marsh area, removal of the sheetpile dam, and
consolidation of the disposal area. Remaining details such as grading and
landscaping the containment area were completed by May 1992. All told, the
project removed more than 100,000 cubic yards of contaminated sediment from
Megginnis Arm.
Streambank stabilization
Following the dredging project, workers (again using section 319 funds) helped
remove exotic or nuisance vegetation (primarily Chinese tallow and alligator
weed) from the littoral area of Megginnis Arm and began to reestablish native
species. The project originally called for planting 150,000 herbaceous wetland
plants and 200 woody plants on 44 acres of the littoral zone. However, these
plans were substantially revised because water levels remained unusually high
and wild seed stock quickly stabilized the area. Ultimately, 40,000 herbaceous
wetland plants and 700 trees were planted in Megginnis Arm to enhance the
basin's natural biological communities.
Effects on Water quality
In general, sampling analyses indicate poorer water quality at the inflows to
the lake (i.e., at Megginnis and Fords Arms) and better water quality in more
open areas. Data trends from the northernmost part of Megginnis Arm show that
the project to remove nonpoint source pollution from the watershed is achieving
success. The values shown in Table 1 are means for the various periods.
Table 1.--Water quality measures in Lake Jackson, 1970 to
1990. |
|
PERIOD |
NO3-NO2
mg/L |
TN
mg/L |
Orth. P.
mg/L |
TP
mg/L |
Chl a
µg/L |
Cond.
µmho/cm |
Turbidity
NTU |
Sfc. DO
mg/L |
Early 1970's |
.054 |
--- |
.015 |
.394 |
--- |
61 |
55.07 |
5.81 |
Late 1970's |
.087 |
.882 |
.046 |
.464 |
16.10 |
87 |
14.10 |
9.64 |
Early 1980's |
.035 |
.559 |
.048 |
.131 |
26.40 |
82 |
21.91 |
10.10 |
Mid 1980's |
.038 |
.427 |
.012 |
.055 |
22.97 |
127 |
9.48 |
8.47 |
Early 1990's |
.010 |
.605 |
.042 |
.073 |
12.54 |
67 |
5.70 |
6.55 |
Mid 1990's |
.008 |
.670 |
.005 |
.037 |
--- |
55 |
--- |
9.10 |
Average |
.039 |
.629 |
.028 |
.192 |
19.50 |
80 |
--- |
8.30 |
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NO3-NO2 = nitrate-nitrite
TN = total nitrogen
Orth. P. = orthophosphorus |
TP = total phosphorus
Chl. a = chlorophyl a |
Cond. = conductivity
Sfc. DO = surface dissolved oxygen |
Nitrate-nitrite, orthophosphorus, total phosphorus, turbidity, conductivity
and chlorophyl a are at their lowest levels in over 20 years. Dissolved oxygen
concentrations at the surface are near all-time highs and, even more important,
were above 8 milligrams per liter at mid-depth and bottom during sampling in
April and July 1996.
The Lake Jackson project exemplifies section 319's contribution to
successful nonpoint source management. This program financed the restoration of
impaired areas and provided for better management of Lake Jackson in the
future. The lake has been designated an "Outstanding Florida Water" and is
included in the state's aquatic preserve program. Consequently, it will
continue to merit attention, protection, and restoration. The partnerships
formed on behalf of Lake Jackson will continue to achieve remarkable
results.
CONTACT: Eric Livingston
Florida Department of Environmental Protection
(904) 921-9915 |
Florida's Silviculture Best Management Practices-
Test Sites Rated "Excellent"
Florida's silviculture NPS management program was cooperatively developed
by the Florida Department of Environmental Regulation, the Florida Division of
Forestry, the U.S. Forest Service, and the forest industry, acting in response
to requirements set forth in Section 208 of the Clean Water Act. In 1976,
responsibility for the program passed to a newly formed Silviculture Technical
Advisory Committee. The major goal of this committee whose members included 12
paper companies, the relevant state and federal agencies, a consulting
forester, the University of Florida School of Forest Resources and
Conservation, and the Florida Forestry Association was to develop a workable
set of best management practices (BMPs) to minimize water quality impacts
associated with forestry activities.
Early developments get results
Between 1977 and 1979, the technical advisory committee, together with the
Department of Forestry, developed a set of practices, including streamside
management zones, minimum bare ground exposure, culvert and cross ditches,
water turnouts, broad-based dips, and a variety of nonstructural BMPs to
minimize stream crossings and other potential nonpoint sources of pollution
created by forestry activities. In 1979, these practices were published as the
Silviculture Best Management Practices Manual. The practices are intended for
use with forestry activities in discretionary zones adjacent to waterbodies.
The width of these zones and the specific BMPs to be used within them are
recommended, depending on a "site sensitivity classification" (SSC), an index
that identifies sedimentation potential. The SSC is based on soil erodibility,
slope, and proximity to a waterbody.
Initial implementation of the program was voluntary. In 1982, as part of
the state's stormwater regulation, forestry activities conducted in accordance
with the BMP manual were exempt from stormwater permitting. When the Department
of Environmental Regulation delegated the stormwater program to the regional
water management districts, the silviculture exemption became a noticed general
permit. Its only requirement was to identify the location and timing of planned
forestry activities.
New issues prompt review
In November 1991, the Department of Forestry held a public meeting to review
the silviculture NPS management program. Participants at this meeting
identified 12 major BMP issues, and a 22-member Technical Advisory Committee
was formed to conduct a comprehensive review of the BMP manual. This committee,
like its prototype, had broad stakeholder representation this time also
including nonindustrial private land owners and conservation organizations. The
review was undertaken in expectation that a revised updated manual would
result. This revision occurred between January 1992 and March 1993, with
funding provided by a 1992 section 319 grant.
The revised Silviculture Best Management Practices greatly increases the
water quality protection associated with forestry activities. Though many of
the original BMPs were retained, their use has been expanded to address other
water resources such as sinkholes, small lakes (less than 10 acres), canals,
and wetlands. Streamside Management Zones were renamed Special Management Zones
(SMZ). The width of the primary zone of the SMZ was expanded from 35 feet to up
to 200 feet, depending on stream width and waterbody classification. In
addition, general ecological considerations and wildlife habitat values were
added as specific BMP objectives. An entirely new set of BMPs were developed
for forestry activities conducted in wetlands or during wet weather.
Training
Once the new manual was published, distribution and training began. In July
1994, the Department of Forestry asked the community to identify individuals
who could serve as BMP trainers within their respective companies, agencies, or
area; and in September, 28 prospective trainers 18 from the forest industry and
10 from state and federal agencies attended a "train the trainers" session in
Tallahassee.
Following that initial training session, the Department of Forestry
conducted BMP workshops throughout the state, beginning in northwest Florida
and working toward the south. By May 1994, 47 BMP workshops had been conducted
with over 1,500 participants, primarily loggers, foresters, forest landowners,
and regulatory agencies' staff. These workshops and distribution of the manual
continue to be a key component of Florida's silviculture program.
Effectiveness assessments
In addition to reviewing the BMP manual, the 1991 Silviculture Technical
Advisory Committee was also charged to evaluate the environmental effectiveness
of the practices. To lead this effort, a BMP Effectiveness subcommittee was
created. Working with the Departments of Forestry and Environmental Protection,
the BMP Effectiveness subcommittee has also designed a monitoring program that
will use recently developed bioassessment protocols to evaluate the impacts of
forestry activities on aquatic ecosystems. This assessment is unrelated to
compliance, since in every case the forestry activities are already in
compliance. The effectiveness study is to determine whether the BMPs actually
protect the water resources as planned.
The effectiveness evaluation, which began in the fall of 1995, includes two
components: long-term BMP effectiveness monitoring and project-duration
monitoring for BMP effectiveness under select, controlled conditions including
before and after disturbance. An example of this second component is the nearly
completed "319 Biological Assessment of the Effectiveness of Forestry Best
Management Practices in Protecting Stream Biota." This project used a before
and after control impact design to sample sites up- and downstream of forestry
activities. The sampling parameters included benthic macroinvertebrates
(resident biota), habitat assessment, and standard physical and chemical
measurements.
Four streams in north Florida were chosen for this project. Then, in
February 1996, on each of these streams, three stations upstream and three
stations downstream of a proposed clear-cutting operation were monitored to
determine the streams before treatment condition. In February 1997,
investigators went back to the identical stations to sample for the after
treatment condition.
At three of the test streams, the reference and test sites were rated
"excellent"; at the other stream, they were "good".
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Next, the data were used to calculate the Stream Condition Index (SCI) for each
stream segment studied. The Stream Condition Index (a composite of seven
invertebrate parameters) has been calibrated to reflect the regional conditions
in undisturbed streams. Its final result supports the effectiveness of the
silviculture BMPs.
Based on the SCI, no statistically significant changes were observed
between the reference and test sites after silviculture activities in which the
BMPs are strictly adhered to during all aspects of the operation. At three of
the test streams, the reference and test sites were rated "excellent"; at the
other stream, they were "good." Results from habitat assessment showed no major
adverse habitat changes from the forestry operations. The project analysts also
found the precision (that is, the repeatability) of the SCI measures very
satisfactory.
The development of forestry BMPs is thus shown to be an effective solution
to a nonpoint source environmental problem.
CONTACT: Eric Livingston
Florida Department of Environmental Protection
(904) 921-9915 |
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