Siskiyou County Municipal Code Art. 15 Other Development

All development, including manmade changes to improved or unimproved real estate for which specific provisions are not specified in these regulations or the building code, shall:

(1) Be located and constructed to minimize flood damage.

(2) Meet the limitations of Section 10-10.1204 of these regulations when located in a regulated floodway.

(3) Be anchored to prevent flotation, collapse or lateral movement resulting from hydrostatic loads, including the effects of buoyancy, during conditions of the design flood.

(4) Be constructed of flood damage-resistant materials.

(5) Have mechanical, plumbing, and electrical systems above the design flood elevation or meet the requirements of ASCE 24, except that minimum electric service required to address life safety and electric code requirements is permitted below the design flood elevation provided it conforms to the provisions of the electrical part of the building code for wet locations.

(6) The standards for construction or modification of bridges within a floodplain are as follows:

(A) Any excavation within the levee section or near bridge supports within the floodway must be backfilled in four-inch to six-inch layers with approved material. The levee section must be compacted to a relative compaction of not less than 90 percent per ASTM D1557-91, dated 1991, which is incorporated by reference and above optimum moisture content. Compaction within the floodway must be to the density of the adjacent undisturbed material.

(B) Compaction tests by a certified soils laboratory may be required to verify compaction.

(C) Bridge piers and bents within the floodway must be constructed parallel to the direction of streamflow.

(D) Bridge piers and bents placed within a floodway to support a widened portion of an existing bridge must be constructed in line with existing bents and piers.

(E) Erosion control may be required on the channel banks or levee slopes upstream and downstream of a proposed bridge.

(F) Drainage from a bridge or highway may not be discharged onto a levee section or streambank.

(G) Plans showing all construction facilities (such as temporary staging, coffer dams, and falsework) which will remain in a floodway during flood season, must be submitted for approval prior to installation of these facilities.

(H) All construction facilities (such as temporary staging, coffer dams, and falsework) must be designed to prevent bank erosion during normal flows and to maintain maximum channel capacity during the flood season.

[(I)

Reserved.]

(J) Stockpiled material, temporary buildings, construction equipment, and detours that obstruct stream flows must be removed from floodways prior to the flood season.

(K) Clearances:

(1) The bottom members (soffit) of a proposed bridge must be at least three (3) feet above the design floodplain. The required clearance may be reduced to two (2) feet on minor streams at sites where significant amounts of stream debris are unlikely.

(2) When an existing bridge being widened does not meet the clearance requirement above the design floodplain, the bottom structural members of the added section may be no lower than the bottom structural members of the existing bridge, except as may be caused by the extension of existing sloped structural members.

(3) When the clearance requirement above design floodplain would result in bridge approach ramp fill in the floodway, the clearance requirement may be reduced to the extent that reasonably balances clearance and fill that would obstruct flow, so as to maintain maximum channel capacity.

(L) Access:

(1) Vehicular access from the roadway to the levee crown may be required at each end of a bridge.

(2) Vehicular access from the levee crown to the floodway and/or the landside levee toe beneath the bridge may be required. Ramps may slope upstream as necessary to provide the access required by this subdivision.

(M) Approved gates must be installed at right angles across the levee crown at all points of access to the levee from each end of a bridge.

(N) Any bridge abandoned or being dismantled must be completely removed and must be disposed of outside the limits of the levee section and floodway.

[(O)

Reserved.]

(P) Pilings, piers, bents, and abutments of bridges being dismantled must be removed to at least one (1) foot below the natural ground line and at least three (3) feet below the bottom of the low water channel.

(Q) Any bridge that is damaged to the extent that it may impair the channel or floodway capacity must be repaired or removed prior to the next flood season.

(R) Replacement railroad bridges must have the soffit members no lower than those of the replaced bridge but are not required to have a specified amount of clearance above the design floodplain.

(S) Bridge replacements and new bridges shall be built at an elevation so that there is no depression in the crown of the levee.

(T) The standards for maintenance of bridges within an adopted plan of flood control are as follows:

(1) The area in and around a bridge site must be kept clear to maintain the design flow capacity.

(2) Trees, brush, sediment, and other debris must be kept cleared from the bridge site and be disposed of outside the limits of the floodway prior to the flood season.

(3) Any accumulation of debris during high flows must be immediately removed from a bridge site and disposed of outside the floodway.

(Ord. No. 25-07, § I, 10-21-2025)

Tanks that serve buildings shall comply with the requirements of the building code. Underground and above-ground tanks that serve other purposes shall be designed, constructed, installed and anchored in accordance with ASCE 24. Tank installation varies by flood zone. Where allowed above ground, tanks can be installed on grade or elevated on platforms or fill. Underground tanks must be installed and anchored to account for saturation of surrounding soils and scour and erosion during flooding. Tanks that are above ground but not fully elevated are allowed only in A zones (A, AE, A1-30, AH, AO, A99, and AR), in which case they must be anchored to resist flood forces. Alternatively, for tanks in A zones, they may be installed inside enclosures or vaults that are designed to be substantially impermeable to flooding ("component protection"). This technique is described in FEMA P-348, Protecting Building Utility Systems from Flood Damage, where it is suggested as a method to protect equipment or groups of equipment that serve non-residential buildings.

Protecting other elements of tanks must also meet the following requirements:

(1) Fill openings, outlets, vents, and cleanouts must either be elevated above the BFE or designed to prevent the entry of floodwater and the loss of contents during flooding.

(2) Controls for electrified equipment shall be elevated above the BFE and electric service shall be supplied by branch circuits that have GFCI protection.

(Ord. No. 25-07, § I, 10-21-2025)

Temporary structures shall be erected for a period of less than 180 days and temporary storage of goods and materials shall be permitted for a period of less than 180 days. Extensions may be granted in accordance with Section 10-10.405 of these regulations. In addition, the following apply:

(1) Temporary structures shall be anchored to prevent flotation, collapse or lateral movement resulting from hydrostatic loads, including the effects of buoyancy, during conditions of the design flood. Fully enclosed temporary structures shall have flood openings that are in accordance with ASCE 24 to allow for the automatic entry and exit of flood waters.

(2) Temporary stored materials shall not include hazardous materials.

(3) Shall meet the limitations of the requirements of Section 10-10.1204 of these regulations, when located in floodways.

(Ord. No. 25-07, § I, 10-21-2025)

Fences in floodways that have the potential to block the passage of floodwaters, such as stockade fences and wire mesh fences, shall meet the limitations of Section 10-10.1204 of these regulations.

(Ord. No. 25-07, § I, 10-21-2025)

Oil derricks located in flood hazard areas shall be designed in conformance with flood loads required by the building code.

(Ord. No. 25-07, § I, 10-21-2025)

Retaining walls and sidewalks and driveways that involve placement of fill in floodways shall meet the limitations of Section 10-10.1204 of these regulations and the requirements for site grading in Chapter 18 of the building code.

(Ord. No. 25-07, § I, 10-21-2025)

Roads and watercourse crossings that encroach into floodways or riverine waterways with base flood elevations where floodways have not been designated, including roads, bridges, culverts, low-water crossings and similar means for vehicles or pedestrians to travel from one side of a watercourse to the other side shall meet the limitations of Section 10-10.1204 of these regulations. Alteration of a watercourse that is part of work proposed for a road or watercourse crossing shall meet the requirements of Section 10-10.503(3) of these regulations.

(Ord. No. 25-07, § I, 10-21-2025)

Above-ground swimming pools, on-ground swimming pools, and in-ground swimming pools that involve placement of fill in floodways shall meet the requirement of Section 10-10.1204 of these regulations.

(Ord. No. 25-07, § I, 10-21-2025)