Florida Department of
Environmental Protection
Soulhwesl Dislricl Ol'lice
13051 North Telecorir I'arkwiiy
Tc~lrplcTerrace. Florida 33637-0926
Via email and U.S.
ail
Mr. Joe Stapf, P.E., Director
Hernando County Utilities Department
21030 Cortez Blvd
Brooksville, FL 34601
Re:
March 2, 2009
February 13, 2009 Letter Regarding Pending Permit No.: 22755-010-SC/01
Hernando Northwest Class I LandEill - Cell 3 Construction Application
Dear Mr. Stapf:
The Department received your letter dated February 13, 2009 seeking
clarification on the status of the permit application for construction of
Cell 3 at the Northwest Solid Waste Management Facility. We have reviewed
the information you provided and would like to respond to and clarify some of
the points you raised.
As you have noted, the timeline for the Cell 3 permitting process has been
longer than that for Cell 2. This is due In most part because the findings
of the subsurface investigations conducted in the Cell 3 footprint differed
from the findings in Cell 2. The Department's heightened concern over
sinkhole potential for Cell 3 was the result of actual sinkhole occurrences
on site since Cell 2 was reviewed and permitted. The GPR survey for Cell 3
identified numerous (42) subsurface anomalies while the Cell 2 GPR survey
only identified three anomalies.
Based on this, the Department requested that additional subsurface
investigation be conducted, and the design of the Cell 3 be modified to
address the increased sinkhole potential for Cell 3. As indicated in your
letter, Florida Geological Survey's initial review of the subsurface
investigation also concluded that the site is located in an area of moderate
to high sinkhole formation. FGS' February 24, 2009 memo updates that
potential to moderate/high to high based on the most recent information
provided by the County.
Your letter indicates that the sinkhole potential at the site is a "well know
factn and has "now more than adequately [been] addressed in the liner
design." This re-design was submitted in response to the Department's
February 22, 2008 Permit Evaluation Letter that indicated that the
preliminary evaluation of your proposed project led staff to the conclusion
that the project could not be recommended for approval. The currently
proposed re-design was received on September 3, 2008, and is under review by
DEP staff. Finalizing the liner design to accommodate the increased sinkhole
potential for Cell 3 has been a large contributor to the extended length of
the permitting process for Cell 3.
As part of the Department's October 3, 2008 R A I #4, we provided the County a
copy of the August 19, 2008 FGS memo for their information and review. In
October the County acknowledged receipt of the memo, but provided no
additional comments indicating that they were in agreement with, or disputed
the findings and conclusions in the FGS memo.
When the County phoned the Department staff in December 2008 to inquire as to
the status of the application, Mr. Harper was informed that the Department
staff was reviewing the information provided and would be making a permitting
decision by the last week in January.
Upon final review of all the information provided and the August 19, 2008 FGS
memo it was determined that we could not recommend approval of the
application based on FGS' review comments and our review of the liner design.
However, since the County had conducted additional subsurface investigation
that FGS had not reviewed and considered in preparing the August 19, 2008
memo, the Department elected to send the additional subsurface investigation
information to FGS for an updated sinkhole evaluation. In order to allow FGSf
review, the County agreed to waive the 90-day review clock until March 27,
2009.
The Department received a copy of FGS's updated memo on February 25, 2009. A
copy of this memo was forwarded to Mr. Harper on February 27, 2009 and is
attached for your information and review. The Department is currently
reviewing the February 24, 2009 FGS memo and the information submitted with
the application to date to determine if reasonable assurance has been
provided that the design meets the requirements of Chapter, 62-701, Florida
Administrative Code, and will adequately perform under the expected potential
and degree of sinkhole occurrence at the site.
The Department will contact the County shortly to set up a meeting to discuss
The result of that review and any additional steps the County should consider
to provide the required reasonable assurance.
Should you have and questions or comment in the meantime, please feel free to
contact Steve Morgan at (813) 632-7600 ext. 3 8 5 or Susan Pelz, P.E., Solid
Waste Program Manager at (813) 632-7600 x 386 or susan.pe1zQdep.state.El.us.
- &-
Sincerely,
3'
L \-"Y
William Kutash, P.G.
Waste Program Administrator
Southwest District
WK / sgm
Attachment
cc:
Scott Harper, Hernando County Solid '/las:e & Recycling Division, 14450 Landfill Road,
Brooksville, FL 34614
Susan P e l z , P.E.. FDEP Tampa ( v i a e-mail)
Florida Department of
Environmental Protection
Memorandum
TO:
Steven Morgan
Environmental Specialist I11
Solid Waste Section
DEP Southwest District Office
THROUGH:
Jon Arthur, PG #I149
Acting State Geologist and Acting Director
Florida Geological Survey
FROM:
Clint Kromhout, PG #2522
Rick Green, PG #I776
Florida Geological Survey
RE:
2nd Review for Sinkhole Formation Probability of the Proposed
Hernando County Northwest Waste Management Facility: Class I
Landfill - Cell 3 Expansion Permit Application
DATE:
February 24th, 2009
The Florida Geological Survey (FGS) was asked to conduct a follow-up and provide
comments regarding the probability of sinkhole formation within the boundaries of the
proposed Hernando County Northwest Class I Landfill - Cell 3 Expansion site located in
northern central Hernando County. The comments herein are based solely upon the
provided landfill permit application geologic and hydrogeologic data supplied by the
Florida Department of Environmental Protection's (DEP) Southwest District Office's
Solid Waste Program and existing data maintained by the FGS. No attempt has been
made to evaluate the engineering measures proposed for use at this site, as those
measures fall outside the technical expertise of the FGS. Newly provided materials
reviewed in preparation for this memorandum include the August, 2008 RAI #3 and
October, 2008 RAIs #4, both from Brown and Caldwell. The assessment of sinkhole
formation probability is based on professional judgment in consideration of data in these
materials and knowledge of regional geologic and hydrogeologic conditions.
Additional borings were conducted to further assess the nature and extent of the
subsurface geologic conditions present at the site and immediate surrounding area.
Unlike the previous sets of borings, of which numerous failed to reach limestone, all but
one boring (out of thirteen) reached limestone yielding a better understanding of the top
of the limestone surface and the thickness of overlying sediments. All of the boreholes
exhibited drilling conditions indicating potential subsurface subsidence-related
conditions such as no recovery, weiglzt of rods, weiglzt of hammer, and lost circulation at
depth.
All of the boreholes encountered weathered limestone. Weathered limestone is not as
E:\Working\CK General Docs\Hernando Cnty NW Class I LF\ Hernand~ClassI~LF-PernutLFollow
UpLReviewLMEM02-022409.doc
Steven Morgan
Page Two
Hernando County Northwest Class I Landfill - Cell 3 Permit Application Review
February 244 2009
well consolidated as unweathered limestone and is more susceptible to dissolution and
breakdown. Seven of the boreholes experienced a loss of circulation when transitioning
into limestone. Three of the boreholes experienced either a weight of hammer or weight of
rods when transitioning into limestone. One borehole experienced n o recovery when
transitioning into limestone. Those noted drilling conditions are good indicators of
poorly consolidated weathered limestone.
The nineteen sinkholes forming in 2003 and 2004 in the northern portion of the landfill's
boundary are definite reason for concern. Brown and Caldwell also "note that the basic
soil profile in the vicinity of the C&DD Landfill where the 2003/2004 sinkholes opened
up is generally similar to that in the vicinity of Cell 3." In addition to the nineteen
sinkholes formed on the site, a buffered 5-mile survey of the Florida Geological Survey's
sinkhole database returned another 13 reported sinkholes. This clearly exhibits a
potential risk for sinkhole development. Both Brown and Caldwell and Ardaman &
Associates, Inc. come to the conclusion that the site has a "moderate to h i g h risk for
sinkhole formation.
With a well-documented active karst environment and potential subsidence related
conditions noted in the boring logs, there is sufficient indication of definite sinkhole
formation risk. Our qualitative assessment of the general probability of sinkhole
formation within the proposed Class I landfill site and surrounding area is
moderate/high to high.
Cc:
J. Arthur
Acting State Geologist and Acting Director
Florida Geological Survey
E:\Working\CK General Docs\Hemando Cnty NW Class I LF\ Hernando_UassI_LF_PermitFoUowUp-Review-MEM02-022409.doc