Item R2
BOARD OF COUNTY COMMISSIONERS
AGENDA ITEM SUMMARY
Meeting Date: 16 November 2005
Division:
Growth Management
Bulk Item: Yes
No X
Depmiment:
Marine Resources
Staff Contact:
George Garrett
AGENDA ITEM WORDING:
Public hearing to consider an ordinance to mnend Section 9.5-293 (e) (4) and (f) (2) of the Monroe County Land
Development Regulations conceming surface water management (stormwater drainage).
ITEM BACKGROUND:
The proposed ordinance is intended to provide clarification and simplification of the County's current surface
water (stonnwater) management criteria, It is based on discussions held between County staff and the
Department of Community Affairs and is predicated on the work developed by Camp, Dresser, and McKee
(CDM), the firm that completed the County's Stonnwater Management Master Plan. CDM also drafted this
proposed ordinance revision.
PREVIOUS RELEVANT BOCC ACTION:
None
CONTRACT/AGREEMENT CHANGES:
NA
STAFF RECOMMENDATIONS;
Approval
TOTAL COST:
NA
BUDGETED: Yes
No
COST TO COUNTY:
NA
SOURCE OF FUNDS:
REVENUE PRODUCING: Yes
No ~ AMOUNT Per Month
Year
APPROVED BY: County Atty X
NA .
DIVISION DIRECTOR APPROVAL:
DOCUMENTATION: Included ~ Not Required
DISPOSITION: AGENDA ITEM NO.:
BC051110doc
10/3 l/2005 2: 13 :00 PM
ORDINANCE NO.
- 2005
AN ORDINANCE OF THE BOARD OF COUNTY COMMISSIONERS OF
MONROE COUNTY, FLORIDA, AMENDING SECTIONS 9.5-293 (e) (4) and (I)
(2), MONROE COUNTY CODE, SURFACE WATER MANAGEMENT
CRITERIA, PROVIDING FOR SEVERABILITY; PROVIDING FOR THE
REPEAL OF ALL ORDINANCES INCONSISTENT HEREWITH; PROVIDING
FOR INCORPORATION INTO THE MONROE COUNTY CODE OF
ORDINANCES; AND PROVIDING AN EFFECTIVE DATE.
\VHEREAS, Monroe County is obligated under Objective 1001.3, Monroe County Year 2010
Comprehensive Plan to adopt a Stormwater Management Master Plan; and
WHEREAS, Monroe County completed and adopted its Stonllwater Management Master Plan in August
of 2001 ; and
WHEREAS, Monroe County similarly is obligated under Policy 1001.1.3 Monroe County Year 2010
Comprehensive Plan, to adopt and update a comprehensive Stormwater Management Ordinance; and
WHEREAS, a Stormwater Management Ordinance was adopted in 1992 as Section 9.5-293, Land
Development Regulations, Surface Water Management Criteria; and
\VHERAS, this Amendment to Section 9.5-293 is based upon the adopted Stormwater Management
Master Plan (200 I) and constitutes a revision to the ordinance based upon current state standards for
surface water management and particularly those guiding discharge to Outstanding Florida Waters,
NO\V, THEREFORE, BE IT ORDAINED BY THE BOARD OF COUNTY
COMMISSIONERS o.F MONROE COUNTY, FLORIDA THAT:
Section 1.
9.5-293 (e) (4), Monroe County Code, is hereby amended as follows:
(4) Water quali~}' considerations: All new surface water management systems will be evaluated
based on the ability of the system to prevent degradation of receiving waters and the ability to conform to
state water quality standards established in chapters 62-1-+-3, 62-1-+-25, and 62-1-+-40, Florida
Administrative Code. Developments which plan to discharge stormwater to Outstanding Florida Waters
will need to provide greater treatment as listed in Section 2.
Section 2.
Sec. 9.5-293 (1) (2), Monroe County Code, is hereby amended to read as follows:
(2) Water quali(v:
a. Projects shall be designed so that discharges do not degrade the receiving water quality will
meet state ,vater quality standards, as set forth in chapters 62-1-+-3, 62-1-+-25 and 62-1-+-40,
Florida Administrative Code.
b. Retention/detention criteria: These criteria are based on the minimum treatment requirements
of Chapter 62-40, F AC principle that the first flush of runoff contains the majority of the
pollutants. The volume which needs to be retained or detained is dependent on the
impervious area percent and whether or not the discharge is to sensitive receiving waters as
defined below method of stormv,'ater management and the land use.
(i) For proiects that do not discharge directly to sensltlve receIvmg waters,
rRetention and/or detention in the overall system, including swales, canals,
green\vays, and similar \vatenyays, shall be provided for the first inch of rainfall or
two and one half (2.5) inches of rainfall times the percent of impervious coverage,
dependent upon the percent of impervious surface '.vhichever is greater. The
retention or detention volumes shall be calculated according to the following
fOffimlae:
For impervious surface area percent of 40 percent or less:
Treatment Volume (acre feet) = Disturbed Area (acres) x 1 (inch) /12 (inches/foot)
For impervious surface area percent greater than 40 percent
Treatment Volume (acre feet) = Disturbed Area (acres) x 2.5 (inches) x Percent
Impervious Area (%)/l00(%)/12 (inches/foot)
Where Treatment Volume (acre feet) is the amount of stormwater treatment
necessary, disturbed area (acres) is defined under item (iii) below, and impervious
surface area percent is the total area of the impervious surface divided by the total
property area times 100.
(ii) Commercial or industrial projects shall provide at least one half (0.5) inch
of dry detention or retention pretreatment us part of the required
retention/detention.
(ii) Projects which discharge directly to sensitive receiving waters shall provide
the dry retention or detention volume according to the following formula:
Treatment Volume (acre feet) = C x Disturbed Area (acres) x 3.2 (inches)/12
(inches/foot)
Where Treatment Volume (acre feet) is the amount of stormwater treatment
necessary, C is the Rational Method runoff coefficient. The Rational Method
coefficient for the water quality treatment volume calculations shall be 0.1 for
pervious areas and 0.95 for impervious areas.
(iiD Commercial or industrial projects shall provide at least one-half (0.50) inch
of dry detention or retention pretreatment prior to discharge to a disposal structure
such as a well, subsurface drainage basin, or trench, as part of the required
retention! detention.
(iii) Systems with inlets in grassed areas '?ill be credited '.vith up to t'.vo tenths
(0.20) inch of the required '.vet detention amount for the contributing areas. Full
credit will be based on a ratio of 5:1 (pervious area/imperyjous area), with the
exception of saltmarsh and buttonwood habitats, '.vhich v..ill require i1 comparable
ration of 7: 1. Grassed areas must be permanently protected from vehicular use and
structural encroachment.
(iv) For the purposes of this section, the "disturbed area" shall include the entire
lot except that the arcas covered by the following "best management practices"
shall be subtracted from the calculation of disturbed area:
1. Forested upland areas I vegetative buffer strips (both natural and
man-made) which will be retained intact and over or through which
vehicular access or travel is not possible and will not occur, and
2. Open water surfaces and wetlands (saltmarsh, buttonwood,
mangroves, or freshwater marsh habitat types).
It will be the responsibility of the applicant to affirmativelv demonstrate that the
best management practices used for the project are designed, constructed, and
maintained properly.
(iv) For the purposes of this section, "discharging directlv to sensitive waters"
shall mean the discharge of runoff via a pipe or channel outfall to the near shore
waters, including canals, for which there is no intervening stonnwater treatment
svstem such as those listed in 9.5~293(f) (2) b (iii). Sensitive receiving waters are
defined as:
Class I waters, Class II waters, Class III waters, Outstanding Florida Waters, and/or
canals connecting with these waters.
(Iv) Projects having greater than forty (40) percent impervious area ""hich
discharge directly to sensiti'.'e receiving water shall provide dry detention or
retention pretreatment equal to fifty (5) percent of the total required depending on
the arrangement of the on site facilities. Sensitive receiving \-vaters are defined as
1. Class lor Class II '.vaters;
2. Class III, Outstanding Florida Waters;
3. Canals connecting ','lith these waters.
(v) Treatment storage recovery shall be estimated using a safety factor of two
for retention systems with supporting infiltration testes).
(v) Water surfuces can be deducted from site areas for ',vater quality
perviousllmpervious calculations.
(vi) Dry detention treatment volumes shall be "offline" allowing a bypass for
storms greater than 1.0.2.5, or 3.2 inches as applicable.
Section 3. In all other respects, 9.5~293, Monroe County Code, Surface Water Management Criteria
will be retained as currently codified.
Section 4. If any section, subsection, sentence, clause or provision of this ordinance is held invalid,
the remainder of this ordinance shall not be affected by such invalidity.
Section 5. All ordinances or parts of ordinances in conflict with this ordinance are hereby repealed to
the extent of said conflict.
Section 6. The provisions of this ordinance shall be included and incorporated in the Code of
Ordinances of the County of Monroe, Florida, as an addition or amendment thereto, and shall be
appropriately renumbered to conform to the uniform numbering system of the Code.
Section 7. This ordinance is hereby transmitted to the Florida Department of Community Affairs
pursuant to Chapter 380 F.S. for review and approval, modification, or rejection.
Section 8. This ordinance shall be filed in the Office of the Secretary of the Sate of the State of
Florida, but shall not become effective until a notice is issued by the Department of Community Affairs or
Administration Commission approving this ordinance pursuant to Chapter 380, F.S
PASSED AND ADOPTED by the Board of County Commissioners of Monroe County, Florida, at
a regular meeting of said Board held on the 16th day of November, 2005.
Mayor Spehar
Mayor Pro Tern McCoy
Commissioner Neugent
Commissioner Rice
Commissioner Nelson
(SEAL)
Attest: DANNY LKOLHAGE, Clerk
BOARD OF COUNTY COMMISSIONERS
OF MONROE COUNTY, FLORIDA
By
By
Deputy Clerk
Mayor/Chairperson
APPROVED AS TO FORM
(~j ',tJ > J ., II >,
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'v:rC1f ;:;.r-. ILl.! CA...,A,L,4/
A TtO~EY~ OFFICE
Department of Marine Resources
2798 Overseas Highway, Suite 420
Marathon, Florida 33050
Voice: (305) 2892507
FAX: (305) 289 2536
Email: ilillI~;:Uc:ggprg~@.D..1QJlrQ.G.countv-t1.g0V
Memorandum
-~
~
,
Board of Count" Commissioners
Mayor Dixie Spehar, DisL I
Mayor Pro Tem Sonny McCoy, Dist. 3
Commissioner George Neugent, Dist. 2
Commissioner David Rice, Dist. 4
Commissioner Murray Nelson, Dist. 5
DATE:
31 October, 2005
TO:
Monroe County Board of Commissioners
FROM:
George Garrett, Director of Marine Resources
SUBJECT:
Proposed Ordinance - Recommended changes to the
Surface Water (Stormwater) Management Criteria
established in Section 9.5-293 (e) (4) and (f) (2).
BACKGROUND
Monroe County is obligated under Objective 1001.3, Monroe County Year
2010 Comprehensive Plan to adopt a Stormwater Management Master Plan.
Monroe County completed and adopted its Stormwater Management Master Plan
in August of 2001. Monroe County similarly is obligated under Policy 1001.1.3
Monroe County Year 2010 Comprehensive Plan, to adopt and update a
comprehensive StoITnwater Management Ordinance. A Stormwater Management
Ordinance was adopted in 1992 as Section 9.5-293, Land Development
Regulations, Surface Water Management Criteria. This Amendment to Section
9.5-293 is based upon the adopted StormwaterManagement Master Plan (2001)
and constitutes a revision to the ordinance based on current state standards for
surface water management and particularly those guiding discharge to Outstanding
Florida Waters.
To add highlight to the adoption of this Ordinance, there have been conflicts in the
review of the current stormwater ordinance as viewed by Florida Department of
Community Affairs (FDCA) and the County. This ordinance seeks to clarify and
resolve those differences in the past interpretation of the ordinance and its
implementation.
BCll51l]() OrdSMMP Rev 050718 Report BOCCdoc
10/31/2005 2: I O:()O PM
The proposed ordinance amending Section 9.5-293 (e) and (f) is attached for your
reVIew.
ANAL YSIS
The proposed ordinance is intended to provide clarification and simplification of
the Countfs current surface water (stormwater) management criteria. It is based
on discussions held between County staff and the Department of Community
Affairs and is predicated on the work developed by Camp, Dresser, and McKee
(CDM), the firm that completed the County's Stormwater Management Master
Plan. CDM also drafted this proposed ordinance revision.
The recommended Ordinance accomplishes the same or similar levels of treatment
for stormwater discharges resulting from the development of a property. At the
same time the calculations for all but stormwater discharges to sensitive receiving
waters as defined (essentially all waters of the County - marine and freshwater)
have been simplified or elarified.
Through past practice, the County developed a simplified users guide to
completing stormwater calculations. Confusion arose over how the calculations
incorporated the "disturbed area" and the compliment, undisturbed or natural areas
into stormwater calculations.
The proposed ordinance breaks up Section 9.5-293 (f) (2) b. (i) into two
complimentary components, each based on the percent of impervious surface for
which stormwater is being managed on residential projects; less than 40 percent ( <
40 %) or greater than forty percent (> 40%). Formulae are provided with which to
make appropriate calculations for either case.
Section 9.5-293 (f) (2) b. (iii) concerning the issue of credits for grassy swale areas
is eliminated, thus creating a more conservative calculation of the retention /
detention requirements. This is compensated slightly through a clarification of the
term "disturbed area" (used in the Simplified Users Guide). The proposed
ordinance provides a new section, Section 9.5-293 (f) (2) b. (iii) (replacing the old
section by the same code citation) which defines the term "'disturbed area," as the
area of the entire lot, but granting specific exceptions for
. Forested areas / vegetative buffer strips (both natural or man-made);
. Open water surfaces and wetlands; and
. Porous pavement such as pavers with a porous media substrate.
2
Finally, clarification is made to Section 9.5-293 (f) (2) b. (ii) concerning
commercial development No specific changes are made to the requirements of the
section, but the intent and purpose for the section is clarified.
RECOMJ\1ENDATION
The Development Review Committee reviewed and recommended approval of the
proposed ordinance on October 6, 2005 as did the Planning Commission on
October 12, 2005 with no suggested revisions.
Staff recommends approval of the proposed ordinance, revising the Surface Water
(Stonnwater) Management Criteria found in Section 9.5-293 (e) and (f)
3