HomeMy WebLinkAboutSUP 06-12; ROBERTSON RANCH HABITAT; FEDERAL EMERGENCY MANAGEMENT ACT; 2009-09-14gifc +-c.1
PLR
Federal Emergency Management Agency
el Washington, D.C. 20472
IND September 14, 2009
CERTIFIED MAIL
RETURN RECEIPT REQUESTED
The Honorable Claude A. Lewis
Mayor, City of Carlsbad
1200 Carlsbad Village Drive
Carlsbad, CA 92008
IN REPLY REFER TO:
Case No.: 09-09-0276P
Follows Conditional Case No.: 07-09-1313R
Community City of Carlsbad, CA
Community No.: 060285
FIRM Panel Affected: 06073C0766 F
06073C0768 F
116
Dear Mayor Lewis:
In a Letter of Map Revision (LOMR) dated April 22, 2009, you were notified of proposed modified flood
elevation determinations affecting the Flood Insurance Rate Map (FIRM) and Flood Insurance Study (FIS)
report for the City of Carlsbad, San Diego County, California. These determinations were for Calavera
Creek - from just upstream of confluence with Agua Hedionda Creek to approximately 3,700 feet upstream
of the confluence; and Detention Basin BiB - from approximately 600 feet northeast of the intersection of
'Th Don Carlos Drive and Don Juan Drive to approximately 1,400 feet northeast of the intersection. The 90-
day appeal period that was initiated on May 8, 2009, when the Department of Homeland Security's Federal
Emergency Management Agency (FEMA) published a notice of proposed Base Flood Elevations (BFEs)
in the North County Times, has elapsed.
FEMA received no valid requests for changes to the modified BFEs. Therefore, the modified BFEs that
became effective on September 8, 2009, remain valid and revise the FIRM and FIS report that were in
effect prior to that date.
The modifications- are pursuant to Section 206 of the Flood Disaster Protection Act. of 1973 (Public
Law 93-234) and are in accordance with the National Flood Insurance Act of 1968, as amended (Title XIII
of the Housing and Urban Development Act of 1968, Public Law 90-448),42 U.S.C. 4001-4128, and 44
CFR Part 65. The community number(s) and suffix code(s) are unaffected by this revision. The
community number and appropriate suffix code as shown above will be used by the National Flood
Insurance Program (NFIP) for all flood insurance policies and renewals issued for your community.
FEMA has developed criteria for floodplain management as required under the above-mentioned Acts of
1968 and 1973. To continue participation in the NFIP, your community must use the modified BFEs to
carry out the floodplain management regulations for the NFIP. The modified BFEs will also be used to
calculate the appropriate flood insurance premium rates for all new buildings and their contents and for the
second layer of insurance on existing buildings and their contents.
If you have any questions regarding the necessary floodplain management measures for your community or the
NFIP in general, please call the Director, Mitigation Division of FEMA in Oakland, California at :3 (510)627-7103.
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If you have any questions regarding the LOMR, the proposed modified BFEs, or mapping issues in general,
) please call the FEMA Map Assistance Center, toll free, at 1-877-FEMA MAP (1-877-336-2627).
Sincerely,
410-M (f c5g7
Kevin C. Long, Acting Chief
Engineering Management Branch
Mitigation Directorate
cc:
Mr. David Hauser
Deputy City Engineer
City of Carlsbad
Mr. Wayne Chang
Chang Consultants
D
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Federal Emergency Management Agency
Washington, D.C. 20472
OCT 2 9 2007'
CERTIFIED MAIL
RETURN RECEIPT REQUESTED
The Honorable Claude A. "Bud" Lewis
Mayor, City of Carlsbad
1200 Carlsbad Village Drive
Carlsbad, CA 92008
IN REPLY REFER TO:
Case No.: 07-09-1313R
Community: City of Carlsbad, CA
Community No.: 060285
104.
Dear Mayor Lewis:
This responds to a request that the Department of Homeland Security's Federal Emergency Management
Agency (FEMA) comment on the effects that a proposed project would have on the effective Fldod
Insurance Rate Map (FIRM), and Flood Insurance Study (FIS) report for San Diego County, California and
Incorporated Areas (the effective FIRM and FIS report for your community), in accordance with Part 65 of
the National Flood Insurance Program (NFIP) regulations. 1n. a letter dated May 22, 2007.
Mr. Wayne W. Chang, P.E., Chang Consultants, requested that FEMA evaluate the effects that the
Robertson Ranch residential subdivision (proposed project), detailed hydrologic and hydraulic analyses,
and updated topographic information along Calavera Creek and Calavera Creek Split Flow would have on
the flood hazard information shown on the effective FIRM and FIS report. The proposed area of revision
along Calavera Creek will extend from just upstream of El Camino Real to approximately 4,700 feet
upstream.
The effective Special Flood Hazard Area (SFHA), the area that would be inundated by base
(1 -percent-annual-chance) flood, for the proposed area of revision along Calavera Creek is designated
Zone AE with Base Flood Elevations (BFEs) determined. BFEs are based on two floodwall condition
analyses: with (perimeter wall in place) and without (perimeter wall removed). BFEs determined for
Calavera Creek on the north side are based on floodwall conditions without the perimeter wall, and BFEs
on the south side represent floodwall conditions with the perimeter wall in place.
The proposed project includes placement of fill, construction of a new detention basin, an Il -foot by
7-foot reinforced-concrete box culvert (outlet culvert), an 84-inch reinforced-concrete pipe diversion
culvert along Cannon Road (diversion culvert); and a split wall. The detention basin is located
approximately 4,400 feet upstream of the confluence of Calavera Creek with Agua Hedionda Creek
(confluence). Flowing entirely into the detention basin, Calavera Creek will exit primarily near the
southerly end of the basin into the outlet culvert. The outlet culvert is located from approximately
3,400 feet upstream to approximately 3,900 feet upstream of the confluence. The wall, located
approximately 350 feet below the upper end of the outlet culvert, splits the flow into two directions. A
portion of the flow will be directed to the diversion culvert and the remainder will continue to flow through
the outlet culvert into the existing Calavera Creek channel. The existing channel of Calavera Creek
extends from just upstream to approximately 3,500 feet upstream of the confluence. The diversion culvert
is located north of the existing Calavera Creek and runs from the split wall to a low lying area, resulting in
a ponding area approximately 1,000 feet northwest of the confluence.
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All data required to complete our review of this request for a Conditional Letter of Map Revision
(CLOMR) were submitted with letters from Mr. Chang.
We reviewed the submitted data and the data used to prepare the effective FIRM for your community and
determined that the proposed project meets the minimum fiocdplain management criteria of the NFIP. The
submitted existing conditions HEC-RAS hydraulic computer model, dated October 16, 2007, was used as
the base conditions model in our review of the proposed conditions model for this CLOMR request. We
believe that, if the proposed project is constructed as shown on the certified submitted plans entitled
Stomi Drain Plans," prepared by O'Day Consultants, and the data listed below are received, the
floodplain boundaries of the base flood will be delineated as shown on the topographic work map entitled
"Calavera Creek HEC-RAS Work Map," certified by Mr. Chang, dated July 23. 2007, a revision to the
FIRM would be warranted.
The submitted HEC- I hydrologic model was used to revise tl:.e effective FIS discharges and to include a
split flow location within the culvert. The existing conditions discharges at approximately 3,300 feet
upstream of the confluence are 1,350 cubic feet per second (cfs). The revised discharge exiting the
detention basin and entering the outlet culvert is 970 cfs. A discharge of 475 cfs is diverted into the
diversion culvert.
As a result of the proposed project and updated topographic information, the BFEs on the north side of the
floodwall will be removed. The BFEs on the south side will decrease throughout the revised reach of
Calavera Creek compared to the existing BFEs. The maximum decrease in BFE, 2.4 feet, will occur
approximately 3,400 feet upstream of the confluence.
As a result of the updated topographic information and proposed project, the SFHA will decrease
compared to the effective SFHA. The maximum decrease in SFHA width, approximately 300 feet, will
occur approximately 800 feet upstream of the confluence. In addition, as a result of the proposed project,
the base flood will be contained in the proposed detention basin, outlet culvert, diversion culvert, and
existing channel from approximately 1.200 feet upstream to approximately 3,500 feet upstreaiii of the
confluence. Also, as a result of the proposed project, the entire reach of Calavera Creek Split Flow will be
removed.
As a result of the proposed project and updated topographic information, the width of the regulatory
floodway will decrease throughout the revised reach of Calavera Creek compared to the effective floodway
width. The maximum decrease in floodway width, approximately 75 feet, will occur approximately
2,100 feet upstream of the confluence. The floodway will be contained in the existing channel of
Calavera Creek. In addition, as a result of the proposed project. the effective floodway will be removed
from approximately 3,300 feet upstream to approximately 4,00 feet upstream of the confluence.
Upon completion of the project, your community may submit the data listed below and request that we
make a final determination on revising the effective FIRM and FIS report.
With this request, your community has complied with all requirements of Paragraph 65.12(a) of
the NFIP regulations. Compliance with Paragraph 65.12(b) also is necessary before FEMA can
issue a Letter of Map Revision (LOMR) when a community proposes to permit encroachments
into the effective regulatory floodway that will cause increases in BFE in excess of those permitted
under Paragraph 60.3(d)(3). Please provide evidence that your community has, prior to approval
of the proposed encroachment, adopted floodplain management ordinances that incorporate the
increased BFEs and revised floodway boundary delineations to reflect post-project conditions, as
stated in Paragraph 65.12(b).
Detailed application and certification forms, which were used in processing this request, must be
used for requesting final revisions to the maps. Therefore, when the map revision request for the
area covered by this letter is submitted, Form 1, entitled 'Overview & Concurrence Form," must
be included. (A copy of this form is enclosed.)
The detailed application and certification forms listed below may be required if as-built conditions
differ from the preliminary plans. If required, please submit new forms (copies of which are
enclosed) or annotated copies of the previously submitted forms showing the revised information.
Form 2, entitled "Riverine Hydrology & Hydraulics Form"
Form 3, entitled "Riverine Structures Form"
Hydraulic analyses, for as-built conditions, of the base flood; and the regulatory floodway; together
with a topographic work map showing the revised floodplain and floodway boundaries, must be
submitted with Form 2.
Effective October 1, 2007, FEMA revised the fee schedule for reviewing and processing requests
for conditional and final modifications to published flood information and maps. In accordance
with this schedule, the current fee for this map revision request is $4,800 and must be received
before we can begin processing the request. Please note, however, that the fee schedule is subject
to change, and requesters are required to submit the fee in effect at the time of the submittal.
Payment of this fee shall be made in the form of a check or money order, made payable in
U.S. funds to the National Flood Insurance Program, or by credit card (Visa or MasterCard only).
The payment, along with the revision application, must be forwarded to the following address:
FEMA National Service Provider
3601 Eisenhower Avenue
Alexandria, VA 22304-6425
As-built plans, certified by a registered professional engineer, of all proposed project elements
Community acknowledgment of the map revision request
A copy of the public notice distributed by your community stating its intent to revise the regulatory
floodway, or a statement by your community that it has notified all affected property owners and
affected adjacent jurisdictions
An officially adopted maintenance and operation plan for the proposed detention basin. This plan,
which may be in the form of a written statement from the community Chief Executive Officer, an
ordinance, or other legislation, must describe the nature of the maintenance activities, the
frequency with which they will be performed, and the title of the local community official who
will be responsible for ensuring that the maintenance activities are accomplished.
After receiving appropriate documentation to show that the project has been completed, FEMA will initiate
a revision to the FIRM and FIS report. Because the BFEs would change as a result of the project, a 90-day
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appeal period would be initiated, during which community officials and interested persons may appeal the
revised BFEs based on scientific or technical data.
The basis of this CLOMR is, in whole or in part, culvert and storm drain project. NFIP regulations, as
cited in Paragraph 60.3(b)(7), require that communities assure that the flood-carrying capacity within the
altered or relocated portion of any watercourse is maintained. This provision is incorporated into your
community's existing floodplain management regulations. Consequently, the ultimate responsibility for
maintenance of the culvert and storm drain rests with your community.
This CLOMR is based on minimum floodplain management criteria established under the NFIP. Your
community is responsible for approving all floodplain development and for ensuring all necessary permits
required by Federal or State law have been received. State, county, and community officials, based on
knowledge of local conditions and in the interest of safety, may set higher standards for construction in the
SFHA. If the State, county, or community has adopted more restrictive or comprehensive floodplain
management criteria, these criteria take precedence over the minimum NFIP criteria.
If you have any questions regarding floodplain management regulations for your community or the NFIP in
general, please contact the Consultation Coordination Officer (CCO) for your community. Information on
the CCO for your community may be obtained by calling the Director, Mitigation Division of FEMA in
Oakland, California, a (510) 627-7175. If you have any questions regarding this CLOMR, please call our
Map Assistance Center, toll free, at I -877-FEMA MAP (1 -877-336-2627).
Sincerely,
,.,
Max H. Yuan, P.E., Project Engineer
Engineering Management Branch
Mitigation Directorate
Enclosures
cc: Mr. John G. O'Donnell, P.E.
Senior Civil Engineer
City of Carlsbad
Mr. Wayne W. Chang, P.E.
Chang Consultants
For: William R. Blanton Jr., CFM, Chief
Engineering Management Branch
Mitigation Directorate