HomeMy WebLinkAbout2.0 Staff ReportBOCC 9/17/01
PROJECT INFORMATION AND STAFF COMMENTS
REQUEST:
APPLICANT:
ENGINEER:
I. Description of the Proposal
Revi ew of a floodplain special use permit request
concerning the Rifle South Wastewater Treatment
Facility
City of Rifle
Schmueser, Gordon , Meyer (SGM)
The City of Rifle ("Rifle") owns and operates an existing wastewater treatment plant known as
the Rifle South Wastewater Treatment Fadlity (WWTF), which was originally built by the Rifle
South Metropolitan District. The project site is located on an alluvial terrace on the south bank of
the Colorado River, just south ofl-70, approximately 1.7 miles west ofthe Rifle exit. The site is
within the boundaries of the Helmer Gulch designated flood plain. The FEMA map designates the
site as lying within Zone A In the 1980's, Rifle took over operation and maintenance of the
facility. In 19 97, the facility was expanded from I 00 , 000 gpd to 250, 000 gpd. The City of Rifle
has recently obtained Garfield County 's approval of another expansion to a capacity of 331 , 000
ga llons per day (gpd). As a result of that review , it was discovered that the City never obtained
the necess ary floodplain special use permit for th e 1997 expansion to place the existing
impro veme nts in the flood plain . This app lication is a request for approval of ex isting and
proposed improvements to be placed in the floodpl ai n.
The application states that the existing facility has been built to conform to the floodplain
regulations . The tops of the berms were built to an elevation one foot above the floodplain
elevation, at an e levation of 5,271 feet. The tops of th e co ncrete overflow structures were
constructed at an elevation of 5,271.2 feet. The top of the concrete chlorin e contact structure is
at an elevation of 5,271.1 feet. The slopes of the lagoon s themselves were built at a 2: 1 slope will
not be damaged in a 100 year flood event. In the event of a shallow flood condition the ponds,
overflow structure, and the chlorine contact structure are protected .
The 2001 expa nsio n will also be built to conform to the floodplain reg ul at ions . The top of the
berms were originally placed one foot above the I 00 year floodplain ele vation , which allowed for
fi ve (5) feet of freeboard. The expansion will .!Jlake use of the freeb oa rd to add additional volume
and detention time for the lagoo ns , without changing the earthwork or benning of the lagoons .
An influent lift stat ion will be install ed to raise the hydraulic grade line of the water in the pond s
to and elevation of 5,269 feet , leavin g two feet of freeboard remaining . The lift station will have a
watertight cover or seal and a below ground wetwell which will have a top of concrete elevation
one foot above the I 00 year floodplain elevation. Mechanical equipment will either be placed one
foot above the I 00 year floodplain elevation, or will be recessed in a pre-engineered structure
with a watertight access hatch. The installation of aerators and an interior baffle wall will not (\
impact the floodplain elevation. The exterior of the overflow struct~res are already above the ~~y..Dl~
year floodplain. . .. .,J,J.,o.JvC\{.1tf);J '.) ,' · 1 "J \:?·(f\ ~~r1~~j,J'joo:v' ~~6 ~~~ ,o'O~ , ,
II. Zoning Regulations and Staff Comments: ;_~~\ ~ ~O,Jrf ~J <J/"(p t::VJY' /
Section 6.08 of the Zoning Resolution describes the a~ministrative procedures to obtain a 0U \~ ·
floodplain special use permit. Any floodplain special use permit application must fulfill the
following criteria:
(J) To assure that all necessaty permits have been received from those governmental agencies
from which approval is required by Federal or State Law, including Section 404 of the Federal
Water Pollution Control Act Amendments of 1972, 33 US. C. 1344.
(2) To determine whether proposed building sites will be reasonably safe from flooding, and that
the structure will be in compliance with the applicable provisions for uses and standards for
construction set forth in this Resolution.
(3) To determine if the proposed development is located in the floodway. If located in the
floodway, assure that encroachment provisions of Section 6. 09. OJ (J)(A) are met.
(4) To assure that adjacent communities, the Colorado Water Conservation Board and Federal
Eme1gency Management Agency have been notified of the proposed watercourse alteration or
relocation.
(5) To assure that the canying capacity of the altered/relocated watercourse is maintained (A.
85-211)
The application addresses and fulfills all these criteria. The wastewater treatment facility holds a
valid NPDES Discharge Permit, a valid Site Application for the 1997 expansion, and an updated
and valid 201 Facility Plan . All built facilities will be protected during flooding . The project is
not located within a floodway and does not propose altering a watercourse, nor will it alter the
capacity of the watercourse.
Section 6.09.02 specifically addresses Flood Fringe/Flood Prone Areas:
(I) Prohibited Uses and Activities. Thefollowing uses and activities are prohibited in the Flood
Fringe/Flood Prone Areas:
(A) The development, use,fill, construction, substantial improvement or alteration on or
above any portion of the Flood Fringe or Flood Prone Areas which alone, or cumulatively
with other activities, would cause or result in the danger of substantial solid debris being
carried downstream by floodwaters.
This project will not cause substantial debris being carried downstream by floodwaters.
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(B) The storage or processing of materials that in times of flooding are buoyant,
flammable, explosive or otherwise potentially injurious to human, animal or plant life.
This project will not result in the storage or processing of materials that would be injurious to humans
in times of flooding.
(C) The disposal of garbage or other solid waste materials.
This project will not result in the disposal of garbage or other solid waste material.
(D) Any obstruction which would adversely affect the efficiency of or restrict the flow
capacity of a designated floodplain so as to cause foreseeable damage to others.
This project will not cause an obstruction which would adversely affect the efficiency or restrict the
flow capacity of a designated floodplain.
(2) Permissible Uses. All Special Uses permitted in the Floodway, and all lawful uses permitted
by the underlying zoning, subject to Section 6. 09. 02(1) of this Regulation and the regulations
concerning the Special Use Permit, are permitted in the Flood Fringe and Flood Prone
Areas.
A wastewater treatment facility is a permissable use in the NRJRD zone district.
(3) Pe1formance Standards. The following pe1formance standards must be met for development
in the Flood Fringe or Flood Prone Areas:
(A) The lowest floor, including basement, of any new or substantially improved building
designed for residential occupancy shall not be less than one (J) foot above the maximum
water elevation of the JOO Year Flood.
All existing and proposed features have ~~elevations one foot above the I 00 year floodplain .
(B) All new construction or substantial improvements shall be reasonably safe from
flooding.
All constructed improvements are safe from flooding.
(C) Any new construction or substantial improvement designed for commercial or
industrial uses shall either:
(i)Elevate the lowest floor level, including basement, to not less than one (J) foot above
the maximum water swface elevation of the 100 Year Flood; or
(ii)Provide flood-proofing improvements so that below an elevation of one (I) foot above
the maximum water elevation of the I 00 Year Flood, the structure, together with
attendant utility and sanitmy facilities, is water tight with walls substantially
impermeable to the passage of water. Structural components shall be capable of
resisting hydrostatic and hydrodynamic loads and effects of buoyancy. Evidence shall
be submitted and certified by a registered professional engineer or architect that the
flood proofing meet the standards as set forth herein.
All constructed and proposed improvements are one foot above the 100 year Floodplain and are safe
from flooding.
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(D) Any proposed development shall be reviewed by the Floodplain Administrator to
insure that the potential for flood damage by the JOO Year Flood is minimized, that all
public utilities and facilities are located, designed and constructed so as to minimize damage
by the 100 Year Flood and that adequate drainage is provided to reduce exposure to flood
hazards.
The potential for flood damage by the I 00 Year Flood has been minimized by either elevating the tops
of the facilities and structures to one foot above the I 00 year floodplain , or by waterproofing any
below-ground features.
(E) All new construction or substantial improvements shall be designed and adequately
anchored to prevent flotation, collapse or lateral movement, be constructed with materials
and utility equipment resistant to flood damage, and be constructed by methods that
minimize flood damage.
Construction has been and will be adequately anchored.
(F) New or replacement water supply systems and sanitary sewage systems shall be
designed so as to minimize or eliminate infiltration of floodwaters. On-site individual
sewage disposal systems shall be located so as to avoid impairment of them or
contamination from them during a 100 Year Flood
The ponds have been designed to prevent floodwater to mix with wastewater.
(G) Within any area subject to sheet flow (Zone "AO" on the Flood Insurance Rate
Maps) all new construction and substantial improvements of residential structures shall
have the lowest floor, including basement, elevated above the highest adjacent grade of the
nearest street to or above the depth number specified on the Flood Maps. Any new
construction or substantial improvements of nonresidential structures in areas identified as
subject to sheet flow shall have the lowest floor, including basement, elevated above the
highest adjacent grade to or above the depth number specified on the Flood Maps, or,
together with attendant utility and sanitary facilities, be completely flood-proofed to or
above the elevation of the water sw:face as specified on the Flood Maps.
All improvements are or will be completely flood-proofed to or above the elevation of the water
surface as specified on the Flood Maps.
(HJ Require that all manufactured homes or those to be substantially improved to
be placed within Zone A on a community's FEMA or FIRM shall be installed using methods
and practices which minimize flood damage. For the purposes of this requirement,
manufactured homes must be elevated and anchored to resist flotation, collapse or lateral
movement. Methods of anchoring may include, but are not limited to, use of over-the-top or
frame ties to ground anchors. This requirement is in addition to applicable State and local
anchoring requirements for resisting wind forces. A manufactured home should be elevated
a minimum of one (J) foot above the base flood level and anchored to the elevated
foundation. (A. 85-211; 89-057; 91-088)
This section is not applicable as neither the existing nor proposed improvements include
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manufactured homes.
Staff finds that the application appears to completely and adequately address the above zoning
regulations.
ill. Recommended Findings:
1. That proper public notice was provided as required for the hearing before the Board of
County Commissioners .
2. That the hearing before the Board of County Commissioners was extensive and complete,
that all pertinent facts , matters and issues were submitted and that all interested parties
were heard at that meeting .
3. That the application is in conformance with the Garfield County Zoning Resolution of
1978, as amended .
4. That for the above stated and other reasons, the proposed floodplain special use permit is
in the best interest of the health, safety, morals , convenience, order, prosperity and welfare
of the citizens of Garfield County .
IV. Recommendation:
Staff recommends the Board of County Commissioners approve the City of Rifle 's floodplain
special use permit application concerning existing and proposed improvements with the following
conditions : ~ \. ;{_ h 1-_~ C. 15Y'~~~ CAA
1. That all representations of the applicant , either within the application or stated at the
hearing before the Board of County Commissioners, shall be considered conditions of
approval;
2. That the Garfield County Zoning Resolution of 1978, as amended , and any other
applicable state or federal laws concerning the 100 yr. floodplain, be complied with ;
3. That all State and Local health standards be complied with ;
4. That a flood elevation certificate, signed and stamped by a licensed (in the State of
Colorado) engineer or su1veyor, be submitted to the Garfield County Planning Depa1tment
within sixty ( 60) days of completion of the proposed construction activities .
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