Chapter 6 — STANDARDS OF CONSTRUCTION

906-01. STANDARDS OF CONSTRUCTION

All new construction or substantial improvements within special flood hazard areas and local flood hazard areas shall comply with the standards set forth in this chapter.

906-02. RESIDENTIAL ELEVATION

New residential structures, or the entire structure being substantially improved/repaired, shall be constructed such that the lowest finished floor is at, or above elevations as follows:

• A. In Zone AO with numbered depth, elevate at least 1.5 feet above that depth given on the FIRM as measured from the highest adjacent grade. When no depth is provided on the FIRM, elevate to at least three feet above the highest adjacent preconstruction natural grade. In either case, the Floodplain Administrator may justify and require a higher elevation.

• B. In Zone A or Zone A-99 where there is no base flood elevation or depth on the FIRM, elevate at least 1.5 feet above the highest value determined by using the methods below:

  1. The elevation taken from historic high-water data interpreted by the Floodplain Administrator;

  2. The elevation shown in a County study;

  3. The elevation as the floodplain is plotted on the topography map; or

  4. The elevation determined using the detailed method from the FEMA publication, FEMA 265, "Managing Floodplain Development in Approximate Zone A Areas- A Guide for Obtaining and Developing Base (100-year) Flood Elevations" dated July 1995.

• C. In areas affected by dual zones, such as AE or local flood hazard, the above A-99 regulations or the base flood elevation for the underlying zone, whichever is higher, shall apply.

• D. In Zone AE, Zone AH, and local flood hazard areas, at least 1.5 feet above the base flood elevation. Building pads for slab-on-grade construction shall be at least one foot above the base flood elevation and the lowest floor must be at least 1.5 feet above the base flood elevation.

• E. In Zone AR as established on the effective Flood Insurance Rate Map, the standards in this chapter shall apply to the construction of new buildings, including elevating floors 1.5 ft above the base flood elevation. The base flood elevation will be determined as follows:

  1. The base flood elevation for developed areas shall be the elevation shown on the FIRM or 3 feet above the highest adjacent grade (before grading occurred), whichever is lower.

  2. In areas that are not designated as developed areas:

     • a. where the AR flood depth is equal to or less than 5 feet above the highest adjacent grade, use the lower of either the AR base flood elevation or the elevation that is 3 feet above the highest adjacent grade; or

     • b. where the AR flood depth is greater than 5 feet above the highest adjacent grade, use the AR base flood elevation

  3. In areas affected by dual zones, such as AE or local flood hazards, the above AR regulations or the base flood elevation for the underlying zone, whichever is higher, shall apply.

• F. New residential construction subject to Urban Level of Flood Protection must have the lowest floor at or above the 200-year flood-water surface elevation or be protected by a levee that provides an Urban Level of Flood Protection.

906-03. NONRESIDENTIAL ELEVATION AND FLOOD-PROOFING

New nonresidential structures or the entire structure being substantially improved shall either be elevated to conform to Section 906-02 or together with attendant utility and sanitary facilities be dry flood-proofed in accordance with FEMA technical bulletin(s) and the following:

• A. Watertight below 1.5 ft above the base flood elevation so that the building walls are substantially impermeable to the passage of water;

• B. Have structural components capable of resisting hydrostatic and hydrodynamic loads including the effects of buoyancy; and

• C. Be certified by a registered professional engineer or architect that the standards of this section are satisfied. Such certification shall be provided to the Floodplain Administrator.

906-04. SPECIAL ELEVATION AND FLOOD-PROOFING.

• A. Attached garages for residential buildings shall be constructed at least one foot above the base flood elevation and all building materials below the minimum floor elevation shall be floodresistant. Garage space under a house must be elevated at least 1' above the base flood elevation except as allowed in 906-04 (C) and (J).

• B. Detached garages, barns, and storage buildings shall be constructed per Section 906-02. At the discretion of the Floodplain Administrator, minor detached structures not meeting these requirements, may be allowed with proper venting and an executed and recorded declaration of land use restriction in a form deemed acceptable to County Counsel, provided they are constructed at or above the base flood elevation.

• C. Applicable only in the Delta Area, the floodplain of the Beach Stone Lakes Area, areas protected by RD1000 levees (Natomas), and areas protected by Reclamation District 800 levees of the Cosumnes River, where building in accordance with 906-04(B) is impractical and such structures are functionally dependent to the land use, barns and garages may be constructed or substantially improved at grade in accordance with FEMA Technical Bulletin 'Wet Floodproofing Requirements' (Technical Bulletin TB3-93, as amended), provided:

  1. The building is constructed of flood-resistant material, fully vented, with at least one opening at least 10 feet wide on at least one side (may be a barn or garage door provided the building is fully vented without including the door opening), and anchored to resist the potential flooding;

  2. All mechanical, plumbing, and electrical equipment in the building, including utilities and sanitary facilities, shall be 1.5 feet above the base flood elevation or flood-proofed below that elevation;

  3. Compliance with these criteria, particularly in deep special or local flood hazard areas may require consultation with a qualified registered professional engineer or architect;

4. The structure should not be used as collateral for a federally backed lender and shall not be considered an insurable structure under the National Flood Insurance Program, nor

shall it be eligible for relief funds in the case of flood damage.

5. The property owner executes and records a declaration of land use restriction with the County indicating the use of the building and assuring that all of the above requirements are met and will be maintained for the useful life of the building and that the building will not be converted to habitable, public, or commercial use.

• D. Non-enclosed parking areas for apartments shall be constructed no lower than 0.50 feet below the base flood elevation and commercial parking lots no more than 1.0 foot below the BFE with signs posting the flood hazard.

• E. Any new built-in swimming pool deck, filter, and pump equipment must be elevated at least 1.0foot above the base flood elevation unless the property owners execute and record a declaration of land use restriction in a form acceptable to County Counsel.

• F. Heating equipment, plumbing fixtures, air conditioning equipment, furnaces, ductwork, electrical panels, solar panels, outlets, switches, and fixtures serving new or substantially improved structures shall be at least 1.5 feet above the base flood elevation.

• G. New solar panels and appurtenances, except as described in (F) above, should be elevated or flood-proofed safely above the base flood elevation. In the latter case, the property owner must execute and record a declaration of land use restriction with the County, in a form acceptable to County Counsel.

• H. The addition of an enclosed area attached to an existing pre-FIRM structure, but not substantial improvement, shall be elevated 1.5 feet above the base flood elevation unless determined by the Floodplain Administrator to be a minor addition in which adding steps would be impractical (e.g. expanding a dining room). In levee-protected areas shown as Zone AE, room additions are allowed with detailed documentation proving the addition is not a substantial improvement.

• I. Lateral additions to post-FIRM buildings (residential or nonresidential) must comply with this ordinance including elevation. Lateral additions must not alter any aspect of the building that had to be met when the building was constructed in compliance with the NFIP and the effective ordinance at the time of original construction. A non-substantial improvement lateral addition may be allowed in special or local flood hazard areas under the following conditions:

  1. If the base flood elevation has not changed the original construction of the building , the addition must be elevated in compliance with this ordinance. An exception may be granted (above the base flood elevation but lacking 1.5 feet- foot vertical freeboard) for

very small dependent expansions such as expanding an existing room or adding a bathroom.

2. If a revised higher base flood elevation is in effect, a lateral addition may be allowed if the addition is elevated at least as high as the existing floor. This includes areas that were mapped Zone X and are now AE due to levee deaccreditation.

• J. Parcels on the Garden Highway, Long Island Road, and other parcels in the State floodway of the Sacramento River may construct wet flood-proofed detached garages or homes on elevated foundations where the lower levels may be used for vehicle parking and incidental storage, subject to a signed and recorded deed restriction approved by County Counsel and subject to approval by state and federal regulators, and by RD1000 for those projects on Garden Highway, in accordance with applicable sections of this ordinance.

906-05. SPECIAL CONSTRUCTION STANDARDS.

• A. Anchoring. All new construction and substantial improvements shall be anchored to prevent flotation, collapse, or lateral movement of the building resulting from hydrodynamic and hydrostatic loads including the effects of buoyancy. All manufactured homes shall also meet the standards of Section 906-07.

• B. Construction materials and methods. Unless specifically described in 906-04, all new construction and substantial improvements shall be constructed with materials and utility equipment resistant to flood damage and using methods and practices that minimize flood damage. Electrical, heating, ventilation, plumbing and air conditioning equipment, and other service facilities shall be designed and/or located to prevent water from entering or accumulating within the components during flooding.

• C. Compacted Fill. If a site is filled above the base flood elevation, then buildings constructed within special or local flood hazard areas must be constructed on compacted fill in accordance with the Construction Specifications or at least 90% density per ASTM-01557 (known as Modified Proctor) and extending at least five feet beyond the building foundation walls before dropping below the base flood elevation and shall include appropriate protection from erosion and scour. The design of the fill must be approved by a registered professional engineer.

• D. Drainage Paths -Zones AO and AH. Within zones AO and AH, drainage paths around buildings on slopes are required to guide floodwater around and away from proposed buildings.

• E. Underground and above-ground tanks shall be designed, constructed, installed, and anchored to prevent flotation, collapse, and lateral movement resulting from floodwater loads, including the effects of buoyancy, hydrostatic pressure, and velocity. Tank inlets, fill openings, outlets, and vents shall be installed 1 foot above the base flood elevation or fitted with covers designed to prevent the inflow of floodwater and outflow of the contents of the tank during the base flood. Water tanks for agricultural operations may be exempted from this elevated venting requirement.

ncluding the effects of buoyancy, hydrostatic pressure, and velocity. Tank inlets, fill openings, outlets, and vents shall be installed 1 foot above the base flood elevation or fitted with covers designed to prevent the inflow of floodwater and outflow of the contents of the tank during the base flood. Water tanks for agricultural operations may be exempted from this elevated venting requirement.

• F. Foundations. Foundations and walls constructed below the base flood elevation shall be vented to equalize hydrostatic pressures. Vent openings shall be permanent openings in the walls that allow for the free passage of water automatically in both directions without human intervention. Such venting shall be on at least two sides of the structure, or enclosure, and have a bottom at no more than 1 foot above the ground elevation. The total area of such venting shall be at least one square inch per square foot of enclosed footprint. Openings may be equipped with screens, louvers, or automated float control in accordance with FEMA Technical Bulletin TB #108 Foundations and walls below the base flood elevation shall be constructed of flood-resistant materials in accordance with FEMA Technical Bulletin TB #2-08. Alternatively, the project proponent may submit a design that will allow for automatic equalization of hydrostatic flood forces on exterior walls, signed and stamped by a registered civil engineer and approved by the Floodplain Administrator. A window, a door, or a garage door is not considered a vent opening. If there are multiple enclosed areas within the foundation, each area must be vented as herewith described.

• G. Non-Conversion. To put current and future tenants and owners on notice that the area below the base flood elevation may not be architecturally finished and converted to living space and that the space may only be used as incidental material storage, building access, and vehicle parking [also see 906-04], a declaration of land use restriction shall be executed and recorded whenever there is a height of more than five feet to assure that foundation area is never converted to living space. The declaration of land use restriction shall be in a form acceptable to the Floodplain Administrator and County Counsel. The Floodplain Administrator shall have the right to inspect for conversion with 72-hour notice.

• H. Basements. A Basement may be constructed with a floor elevation that conforms to Section 90602.

• I. Electrical panels for uses other than new or substantially improved residential, commercial, or industrial structures (such as agricultural wells and barns) in areas protected by RD1000 levees

(Natomas area), and in the Delta Area may be installed below the base flood elevation. In this case, marine-grade (or otherwise flood-resistant) equipment is recommended.

• J. Commercial solar power plants are treated as development (Section 906-06), and any structures or electrical panels for such facilities shall be elevated or flood-proofed at least 1.5' above the base flood elevation and designed and anchored in accordance with this section. A declaration of land use restriction in a format approved by County Counsel must be recorded if any part of the commercial solar development will be lower than 1.5' above the base flood elevation.

• K. Any structure with the increased cost of compliance flood insurance coverage that sustains flood damage on two or more occasions exceeding 25 percent of the market value (measured before the recent damage occurred) but less than 50 percent in any one event should, as such insurance allows, elevate or otherwise mitigate the flood risk.

906-06. STANDARDS FOR NEW DEVELOPMENT

All development plans and grading plans shall:

• A. Identify special or local flood hazard areas and the elevation of the base flood

• B. Provide the elevation of proposed buildings and pads, and ensure the proposed pads will be at least one foot above the base flood elevation and meet minimum floor requirements per section 906-02. If the site is filled above the base flood elevation, the constructed pad elevations shall be as-built surveyed by a registered professional engineer or surveyor, compacted in accordance with 906-05 (C), and certified results shall be provided to the Floodplain Administrator for review and submittal to FEMA for map revision.

• C. Be designed in accordance with this Code and the County Improvement Standards to minimize flood damage.

• D. In addition to elevation and flood-proofing requirements for structures described herein, all floodplain management permits for new public utilities (such as pump stations, power plants, and communications) should assure that the flood damageable facility is elevated 1.5 feet above the base flood elevation or certified flood-proof. Utilities deemed critical to emergency management (including sewer, gas, electrical, and water systems) should be protected from damage in the 200-year flood event (in accordance with the Central Valley Flood Protection Board Urban Level of Flood Protection requirements).

• E. Provide a drainage system report in accordance with the County Improvement Standards with a narrative describing the existing and proposed stormwater management system, including all

discharge points, collection, conveyance, and stormwater storage facilities.

• F. Provide a drainage system map including, but not limited to, sub-watershed boundaries and the property's location within the larger watershed, pre development and post-development terrain at 1-foot contour intervals, and the location of all existing and proposed drainage features. Include a plan of the parcel showing applicable proposed revisions to pre-development and post development surface drainage flows.

inage system map including, but not limited to, sub-watershed boundaries and the property's location within the larger watershed, pre development and post-development terrain at 1-foot contour intervals, and the location of all existing and proposed drainage features. Include a plan of the parcel showing applicable proposed revisions to pre-development and post development surface drainage flows.

• G. Before any proposed filling in a floodplain is permitted and when a detailed hydraulic model is not available, the volume that will be occupied by the permitted fill below the base flood elevation shall be compensated for and balanced by a hydraulically equivalent volume of excavation taken from below the base flood elevation. This is a general rule on creeks and channels in riverine flow, thus is not necessary on land within the island side of levees in the Delta Area, Beach Stone Lake, and very wide levee breach floodplains of the Cosumnes River floodplain.

• H. No new construction or substantial improvements or development may occur without the approval of the Floodplain Administrator and without demonstrating that the cumulative effect of the proposed development when combined with all the existing and anticipated development will not have adverse impacts on downstream, upstream, or adjacent properties, and the FEMA mapping requirements of section 905-08 are met.

• I. In floodplains of natural streams and natural stream tributaries, and other streams subject to review and approval by the Floodplain Administrator, grading causing an adverse impact, as measured at the property lines of the parcel(s) being developed, must be approved by the Floodplain Administrator.

• J. Stormwater calculations by a professional civil engineer shall be submitted to the Floodplain Administrator, including but not limited to, detention basin sizing, storm drain pipe sizing, and overland flow path design.

• K. The majority of stormwater management features in the urban services area of the County are maintained in a routine manner funded by the Storm Water Utility; however, on occasion, an operation and maintenance procedure for peculiar features will require a supplemental funding agreement.

• L. The applicant shall obtain all required state and federal permits.

• M. All new development within Zone A that creates more than 4 lots or involves more than 5 acres of land shall provide base flood elevation data to the Floodplain Administrator and meet FEMA

mapping requirements per section 905-08. The base flood elevation shall be determined to the satisfaction of the Floodplain Administrator.

• N. Development master plan floodplain models for specific plan areas must establish the existing condition base flood elevation and assure no adverse impact in accordance with this ordinance. The project proponent shall submit the existing condition model to the Floodplain Administrator prior to publishing the environmental impact report for that development proposal. When the watershed area is greater than one square mile, the existing condition floodplain model must be submitted to FEMA for approval before improvement plans are approved for the development. The project proponent must obtain a CLOMR (Conditional Letter of Map Revision) from FEMA for any actions affecting the floodplain before those actions are constructed.

• O. Development projects subject to the Urban Level of Flood Protection (ULOP) as determined through §902-57.1, must be planned and designed to achieve the Urban Level of Flood Protection developed by the State of California Department of Water Resources. The County of Sacramento must make a finding for projects subject to ULOP, per §5.11 of the Sacramento County Zoning Code. Substantial evidence, such as a study prepared by a registered engineer, must be provided to support any finding(s).

906-07. STANDARDS FOR MANUFACTURED HOMES.

• A. All new or substantially improved manufactured homes that are placed on a foundation at a site located outside of a manufactured home park and within a special flood hazard area or local flood hazard area shall be constructed per Section 906-02 and be anchored in accordance with Section 906-05(A).

• B. All new manufactured home parks or subdivisions or expansion of existing parks or subdivisions shall be constructed such that the concrete home pads are at least one foot above the base flood elevation.

• C. All manufactured homes to be placed or substantially improved on sites in an existing manufactured home park or subdivision within a special flood hazard area or local flood hazard area except as otherwise provided in this section or by other standards required by the State regulators of manufactured home parks will be securely fastened to an adequately anchored foundation system to resist flotation, collapse, and lateral movement, and be elevated so that either:

  1. The lowest floor of the manufactured home is 1.5 feet above the base flood elevation.

  2. The manufactured home chassis is supported by reinforced piers or other foundation elements of at least equivalent strength that are no less than 36 inches in height above grade.

• D. On a pad or space in a manufactured home park at which a manufactured home has incurred substantial damage caused by floodwater, the repaired home and all subsequently placed homes must be elevated at least 1.5 feet above the base flood elevation on a secure and anchored foundation.

• E. Upon the completion of an installation described in (A) through (C) above, the elevation of the lowest floor shall be certified by a registered professional engineer or surveyor and verified by the community building-inspector to be properly elevated. Such certification and verification shall be provided to the Floodplain Administrator.

906-08. STANDARDS FOR RECREATIONAL VEHICLES

All new recreational vehicle parks or additions to parks in a special or local flood hazard area shall clearly post the hazard and methods of flood warning. All recreational vehicles placed on sites within special flood hazard areas or local flood hazard areas shall:

• A. Be on wheels, mobile, fully licensed, attached to the site only by quick disconnect type utilities and security devices; and

• B. Have no attached additions on adjoining foundation.

906-09. FLOODWAYS.

• A. New construction, substantial improvements, and other development within a floodway is prohibited unless certification by a registered professional engineer is provided which demonstrates to the satisfaction of the Floodplain Administrator that such development will not result in any increase in the base flood elevation.

• B. All new construction, substantial improvements, and other development within floodways that satisfy the requirements of this section shall also comply with all other applicable provisions of this ordinance.

• C. All new construction, substantial improvements, and other development within floodways that will cause increases in the base flood elevation shall only be permitted if the County has applied to the Federal Emergency Management Agency for modification of the flood insurance

rate maps and has received conditional approval of such modifications, and all other applicable provisions of this ordinance are satisfied.

906-10. CERTIFICATION REQUIREMENTS

When development occurs on property that has been identified by the Floodplain Administrator as being located in a special flood hazard area, the following shall be certified by a registered civil engineer or licensed land surveyor and provided to the Floodplain Administrator:

• A. Elevation of the lowest floor of all detached buildings

• B. Elevation of the lowest adjacent grade

• C. Elevation of the highest adjacent grade

• D. Elevation to which a structure has been flood-proofed (if applicable)

• E. Elevation of swimming pools, utilities, and any other structures, as requested by the Floodplain Administrator

• F. Venting per 906-05(E)

• G. All known sources of 100-year flooding and which of those is used for certification

906-11. SITE DEVELOPMENT IN THE FLOODPLAIN

Unless otherwise approved by the land use authority, the following shall apply:

• A. When land is divided, there must be a minimum buildable area for each created lot above the base flood elevation, as follows:

• B. Access crossing the floodplain must be above the 10-year flood and no more than 1-foot deep in the 100-year flood.

• C. Commercial and industrial development may not allow parking more than 1-foot below the base flood elevation.

• D. Fencing on the ground that is below the base flood elevation shall be constructed as follows:

  1. In the floodplain fringe and parallel to the flow shall be open-style

2. Nonparallel fencing in the floodplain shall allow free flow of water such as 5-wire or 4- board horizontal rail type.

   3. Fencing in a floodway is not allowed except upon proof that there is no adverse impact to upstream or adjacent properties and approval by the Floodplain Administrator.

   4. Alternative designs may be considered, such as break-away fencing, if the applicant submits a design to the Floodplain Administrator for consideration.

• E. Fee title or easement over floodway areas shall be dedicated to the County unless determined inappropriate by the Floodplain Administrator.

• F. The Delta Area, Beach Stone Lakes Area, river side of the levees on the Sacramento River, the Natomas Area, and the floodplain east of Natomas East Main Drain are exempt from the above sections (A), (B), (C) and (E).