1475 BEACH AVE - DEMO PERMIT Walker, Jennifer
From: Carper, RI
Sent: Thursday, ' ✓ember 06, 2014 11:06 AM
To: info @jalon, •om
Cc: Layton, Doi llas; Graham, Shirley; Walker, Jennifer; Hubsch, Jeremy
Subject: Building Pe nit re. 1475 Beach Ave (Corral residence)
Attachments: LDR 24-6E ''tormwater.doc; 1475 Beach Ave-onsite Retention w-grnd.xlsx
Demolition permit for existing house has been approved by Public Works. Following comments will need
resolution before follow-on building permit will be approved:
City Code requiring on-site storage does not differentiate between drainage to the street and drainage
to the beach or other drainage feature (see attached excerpt). On-site storage will be required for total
increase in impervious area. Pre and Post-development impervious surface area calculations must reflect the
entire parcel. Attached storage requfr'ement spreadsheet shows estimate developed from data on plans dated
10-15-14 provided with demo appli )n.
Proposed manner of install; . ,_ , of pavers for drives and walkways / pool deck does not qualify for 50%
impervious area credit (detail sheet ` 3). Pavers must be installed in accordance with !CPI standards to receive
credit(http://www.icpi.orq/design).
City Code restricts drivewa; v;dth in right of way to 20'. Because existing property exceeds that width,
applicant will be allowed to return t irrent width, but cannot exceed 50% impervious area in the right of way.
Ricky L. Carper, P.E. -
Deputy Public Works Director
City of Atlantic Beach 't,1
1200 Sandpiper Lane
•
Atlantic Beach, FL 32233
rcarper ancoab.us ,
PH: (904)247-5834 , '
Fax: (904)247-5843 ' A�
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Sec. 24-66. Stormwater, Drainage, Storage and Treatment Requirements.
(a) Topography and Grading. All Lots and Development sites shall be constructed and
graded in such a manner so that the stormwater drains to the adjacent Street, an existing
natural element used to convey stormwater(See section 22-303, definitions: Stormwater
Management System), or a City drainage structure after meeting on-site storage requirements,
as set forth within this Section. The City shall be provided with a pre-construction topographical
survey prior to the issuance of a Development Permit and a post-construction topographical
survey prior to the issuance of a Certificate of Occupancy. Elevations in all topographic surveys
will be referenced to NAVD 1988. Said surveys shall be prepared by a licensed Florida
surveyor, and the requirement for either or both surveys may be waived by the Director of Public
Works if determined to be unnecessary.
Except as required to meet Coastal Construction Codes as set forth within a valid permit
from the Florida Department of Environmental Protection; or as required to meet applicable
flood zone or stormwater regulations as set forth herein, the elevation or topography of a
Development or Redevelopment Site shall not be altered.
(b) On-Site Storage. The Applicant shall be required to provide on-site storage, such that there
is no increase in the rate or volume of flow to off-site, from every developed or redeveloped
Parcel, and for any addition or modification that increases the impervious surface area on a
developed lot by 10% or 400 SF, whichever is smaller and provide documentations and
calculations to demonstrate compliance. Development Projects previously permitted by the St.
Johns River Water Management District (SJRWMD), which have an in-compliance retention or
detention system that collects and controls run-off, are exempt, however a copy of the
Engineer's Certification of As-Built Construction to the SJRWMD must be submitted to the City
before issuing building permits for individual lot construction may begin. The requirement for
on-site storage may be waived by the Director of Public Works if storage is determined to be
unnecessary or unattainable. If on-site storage is required, an As-Built survey, signed and
sealed by a licensed Florida surveyor, documenting proper construction and required volume of
the storage system, must be submitted to the Director of Public Works prior to permit closeout
or issuance of a Certificate of Occupancy. For an under-ground system, a notarized letter from
the General Contractor, along with red-lined plans and construction photographs, will be
sufficient to document proper construction.
Volume calculations for Lots that require on-site storage should be based on the difference in
run-off volume generated by the new impervious area ("delta volume") and would be calculated
by:
V=CAR/12, where
V = volume of storage in cubic feet,
A = area of the lot in square feet,
R = 25 year and 24 hour rainfall depth (9.3 inches) over the lot area, and
C = run-off coefficient, which is 0.6 for the 50% maximum imperviousness, 0.4 for 25%
imperviousness, and 0.2 for 0% imperviousness.
This delta volume (post V minus pre-V in cubic feet) must be stored at least 1 foot above the
wet season water table and below the overflow point to off-site (in many cases this may be the
adjacent road elevation). As an option, and as approved by the Director of Public Works, the
owner of the parcel to be developed or redeveloped may implement, at the applicant's cost, off-
site storage and necessary conveyance to control existing flood stages off-site.
(c) Flood Plain Storage. There shall be no net loss of storage for areas in the 100-year
floodplain, where a floodplain elevation has been defined by either the Federal Emergency
Management Agency (FEMA) on Flood Insurance Rate Maps (FIRMs), the 1995 Stormwater
Master Plan, the Core City project, or the 2002 Stormwater Master Plan Update (e.g., Hopkins
Creek). Site grading shall create storage on-site to mitigate for filling of volume on-site. This
storage is in addition to the storage required for the increase in Impervious Surface Area. The
Applicant shall provide signed and sealed engineering plans and calculations documenting that
this `no net loss' requirement is met.
(d) Stormwater Treatment. For all new Development or redevelopment of existing properties,
excluding Single and Two-family uses, where construction meets limits for requiring Building
Code upgrades, stormwater treatment shall be provided for a volume equivalent to either
retention or detention with filtration, of the run-off from the first one (1) inch of rainfall; or as an
option, for facilities with a drainage area of less than one hundred (100)acres, the first one-half
(1/2) inch of run-off pursuant to Chapter 62-25, Florida Administrative Code (FAC). No discharge
from any stormwater facility shall cause or contribute to a violation of water quality standards as
provided in Section 62.302 of the Florida Administrative Code. This treatment volume can be
included as part of the on-site storage requirement in item d (2) of this Section.
(e) NPDES Requirements. All construction activities shall be in conformance with the
City's National Pollutant Discharge Elimination Systems (NPDES) permit, in addition to the
requirements of the Water Management District and the Florida Department of Environmental
Protection. NPDES requirements include use of Best Management Practices (BMPs) prior to
discharge into natural or artificial drainage systems. All construction projects of one acre or
more require a stand-alone NODES permit. Site clearing, demolition and construction on any
size site may not commence .until site inspection and approval of the proper installation of a
required Best Management Practices erosion and sediment control plan is completed.
(f) Enforcement. Subsequent to approval of a property owner's final grading, including on-site
and/or flood plain storage and stormwater treatment, the improvements shall be maintained by
the property owner. Failure to maintain the improvements will require restoration upon
notification by the Director of Public Works, within a stipulated time frame. If restoration is not
timely completed, the City shall have the right to complete the restoration, and the City's actual
cost incurred, together with a charge of 100% of said costs to cover the City's administrative
expenses, shall be charged to the owner.
(g) Minor waivers to Impervious Surface Area limits. The Director of Public Works shall
have the authority to waive the Impervious Surface Area up to five (5) percent of the established
limit upon demonstration by the property owner or Applicant that preceding stormwater
standards shall be maintained and upon showing of good cause and need for the increased
Impervious Surface Area which shall be based upon the inability to meet limits due to site
constraints or pre-existing conditions. Any reduction shall be calculated based upon the total
square footage of Lot Area and the square footage of the allowed Impervious Surface Area. For
example, on a 7500 square foot lot, the allowed Impervious Surface Area is 3,750 square feet,
and the maximum Impervious Surface Area permitted to be waived in accordance with this
provision is 187.5 square feet.
rs rt �, Comp. By: RLC
Date: 11/6/2014
—es: >/
Public Works Department
City of Atlantic Beach
Permit No: 14-Demo-349
Address: 1475 Beach Ave
Required Storage Volume
Criteria:
Section 24-66 of the City of Atlantic Beach's Zoning, Subdivsion, and Land Development Regulations
requires that the difference between the pre-and postdevelopment volume of stormwawter runoff be
stored on site. Volume of Runoff is defined as follows:
V=CAR/12
Where: V=Volume of Runoff
C=Coefficient of Runoff
A=Area of lot in square feet
R=25-yr/24-hr rainfall depth(9.3-inches for Atlantic Beach)
Predevelopment Runoff Volume:
Lot Area(A) = 14,030 ft2
Runoff Coefficient
.rea Lot Area
Description (ft') (ft2) "C" Wtd "C"
Impervious 2,426 14,030 1.00 0.17
Pervious 11;604 14,030 0.20 0.17
Runoff Coefficient(C)= 0.34
Runoff Volume
V= 0.34 x 14,030 x 9.3 / 12
V= 3,679 ft3
Postdevelopment Runoff Volume:
Lot Area(A) = 14,030 ft2
Runoff Coefficient
Area Lot Area
Description (ft2) (ft2) "C" Wtd"C"
Impervious 8 14,030 1.00 0.49 ISA = 49.4%
Pervious ,,u2 14,030 0.20 0.10
Runoff Coefficient(C)= 0.60
Runoff Volume
V= 0.60 x 14,030 x 9.3 / 12
V= c 4'0 ft3
Required Storage Volume
DV= Postdevek/pment Runoff Volume-Predevelopment Runoff Volume
DV= 6, 70 3,679
DV= 2.791 ft3
Retention 1475 Beach Ave-onsite Retention w-gmd 11/6/2014