Washington County, WI Article IV Floodplain Zoning

§ 275-14 General provisions; Floodplain Zoning District.

A. Areas to be regulated: Areas regulated by this chapter shall include all lands in the unincorporated limits of Washington County, Wisconsin, that would be covered by the regional flood identified as Zones A, AO, AH, A1-30, AE, on the Flood Insurance Rate Map.

B. Official maps and revisions: Floodplain zoning district boundaries are designated as Zones A, A1-30, AE, AH, AO, on the Flood Insurance Rate Maps (FIRMs) based on flood hazard analyses summarized in the Flood Insurance Study (FIS) listed in Subsection C(1) below. Additional flood hazard areas subject to regulation under this article are identified on maps based on studies approved by the DNR and adopted by Washington County and listed in Subsection C(2) below. These maps and revisions are on file in the office of the Washington County Planning and Parks Department.

C. Official Floodplain maps; Flood Insurance Rate Map (FIRM) Panels.

(1) Based on the Flood Insurance Study (FIS).

(a) Official Maps: Based on the Flood Insurance Study (FIS):

[1] Flood Insurance Rate Map (FIRM), panel numbers 55131C0017F, 55131C0019F, 55131C0036F, 55131C0038F, 55131C0039F, 55131C0041E, 55131C0042E, 55131C0043E, 55131C0044E, 55131C0061E, 55131C0062E, 55131C0063E, 55131C0064E, 55131C0066E, 55131C0067E, 55131C0068E, 55131C0069E, 55131C0086E, 55131C0087E, 55131C0088E, 55131C0089E, 55131C0091E, 55131C0093E, 55131C0107F, 55131C0109F, 55131C0117F, 55131C0119F, 55131C0126F, 55131C0127F, 55131C0128F, 55131C0129F, 55131C0131E, 55131C0132E, 55131C0133E, 55131C0134E, 55131C0136F, 55131C0137F, 55131C0138F, 55131C0139F, 55131C0141E, 55131C0142F, 55131C0143E, 55131C0151E, 55131C0152E, 55131C0153E, 55131C0154E, 55131C0156E, 55131C0157E, 55131C0158E, 55131C0159E, 55131C0161F, 55131C0162E, 55131C0164E, 55131C0166E, 55131C0167E, 55131C0168E, 55131C0169E, 55131C0176E, 55131C0177E, 55131C0178F, 55131C0179F, 55131C0181E, 55131C0183E, 55131C0186F, 55131C0187F, 55131C0188E, 55131C0189F, 55131C0191F, 55131C0206F, 55131C0207F, 55131C0208F, 55131C0209F, 55131C0216F, 55131C0217F, 55131C0218F, 55131C0219F, 55131C0226F, 55131C0227F, 55131C0228F, 55131C0229F, 55131C0233F, 55131C0234F, 55131C0236F, 55131C0237F, 55131C0238F, 55131C0239F, 55131C0241F, 55131C0242F, 55131C0243F, 55131C0244F, 55131C0252E, 55131C0256F, 55131C0268F, 55131C0269F, 55131C0279F, 55131C0281F, 55131C0288F, 55131C0306F, 55131C0307F, 55131C0308F, 55131C0309F, 55131C0326F, 55131C0327F, 55131C0328F, 55131C0329F, 55131C0331F, 55131C0333F, dated 2-20-2026;

[2] Flood Insurance Rate Map (FIRM), panel numbers 55131C0144E, 55131C0163E, 55131C0193E, 55131C0231F, 55131C0232E, 55131C0251E, 55131C0253E, 55131C0254E, 55131C0257E, 55131C0258E, 55131C0259E, 55131C0261F, 55131C0262E, 55131C0263F, 55131C0264E, 55131C0266E, 55131C0267E, 55131C0276E, 55131C0277E, 55131C0278E, 55131C0286E, 55131C0287E, 55131C0289E, dated 2-25-2022;

[3] Flood Insurance Rate Map (FIRM), panel number 55131C0037F, dated 11-20-2013;

[4] Flood Insurance Study (FIS) for Washington County, dated 2-20-2026.

Approved by: The DNR and FEMA

(b) Official Maps: Based on other studies. Any maps referenced in this section must be approved by the DNR and be more restrictive than those based on the FIS at the site of the proposed development.

[1] A Dam Failure Analysis for Ehne Dam, prepared by Stormwater Solutions Engineering dated December 15, 2011, and approved by the Department of Natural Resources on August 15, 2012, including:

[a] Map attached to the referenced Analysis as Exhibits, consisting of two sheets numbered DFA.2 and DFA.3, titled "Dam Failure Analysis Hydraulic Shadow."

[b] Floodway data table presented as "Table 5: HEC-RAS Results" in the referenced Analysis. The value in the column headed "Dam Failure Max W.S." is the governing elevation.

[c] No flood profiles are included with this study.

[2] A Dam Failure Analysis for Lucas Lake Dam, prepared by GRAEF dated March 11, 2016, with separate exhibits submitted on April 13, 2016, and approved by the Department of Natural Resources on May 6, 2016. The governing zoning documents based on the Analysis are as follows:

[a] Map based on the referenced Analysis, consisting of one sheet, titled "Hydraulic Shadow Map - April 13, 2016 - Lucas Lake Dam."

[b] Floodway Data Table based on the referenced Analysis, consisting of one sheet, titled "Lucas Lake Dam Failure Analysis - Floodway Data Table - April 13, 2016." The value in the column headed "Lucas Lake Dam Failure Profile" is the governing elevation.

[c] Flood Profile based on the referenced Analysis, consisting of one sheet, titled "Lucas Lake Dam Failure Analysis - Flood Profile - April 13, 2016." The profile indicated as "WS DFA" in the legend is the governing profile.

[3] Washington County and Incorporated Areas Flood Storage Districts, Panel(s) 1-12, effective 2-20-2026.

(2) Establishment of floodplain zoning districts. The regional floodplain areas within the jurisdiction of this chapter are hereby divided into four districts, defined as follows:

(a) The "Floodway District" consists of the channel of a river or stream and those portions of the floodplain adjoining the channel that are required to carry and discharge the regional floodwaters and are contained within AE Zones as shown on the FIRM, or within A Zones shown on the FIRM when determined according to § 275-17E.

(b) The "Floodfringe District" consists of that portion of a riverine special flood hazard area outside the floodway within AE Zones on the FIRM, or, when floodway limits have been determined according to § 275-17E, within A Zones shown on the FIRM.

(c) The "General Floodplain District" consists of all riverine areas which have been or may be covered by floodwater during the regional flood in which a floodway boundary has not been delineated on the FIRM and also includes shallow flooding areas identified as AH and AO Zones on the FIRM.

(d) The "Flood Storage District" is that area of the floodplain where storage of floodwaters is calculated to reduce the regional flood discharge.

(3) Locating floodplain boundaries. Discrepancies between boundaries on the Official Floodplain Zoning Map and actual field conditions shall be resolved using the criteria in Subsection C(4)(a) or (b) below. If a significant difference exists, the map shall be amended according to § 275-22. The administrator can rely on a boundary derived from a profile elevation to grant or deny a land use permit, whether or not a map amendment is required. The administrator shall be responsible for documenting actual predevelopment field conditions and the basis upon which the district boundary was determined and for initiating any map amendments required under this section. Disputes between the administrator and an applicant over the district boundary line shall be settled according to § 275-21F(4) and the criteria in Subsection C(4)(a) and (b) below. Where the flood profiles are based on established base flood elevations from a FIRM, FEMA must approve any map amendment or revision pursuant to § 275-22.

(a) If flood profiles exist, the map scale and the profile elevations shall determine the district boundary. The regional or base flood elevations shall govern if there are any discrepancies.

(b) Where flood profiles do not exist for projects, the location of the boundary of Zone A, AO shall be determined by the map scale.

(4) Removal of lands from floodplain.

(a) Compliance with the provisions of this chapter shall not be grounds for removing lands from the Floodplain District, unless they are removed by filling to a height of at least two feet above the regional flood elevation, the fill is contiguous to land lying outside the Floodplain District, and the map is amended pursuant to § 275-22 of this chapter.

(b) The delineation of any of the Floodplain Districts may be revised by the community where natural or man-made changes have occurred and/or where more detailed studies have been conducted. However, prior to any such change, approval must be obtained from the Wisconsin Department of Natural Resources and Federal Emergency Management Agency. A completed Letter of Map Revision is a record of this approval. The floodplain administrator shall not sign a community acknowledgement form unless all criteria set forth in the following paragraphs are met:

[1] The land and/or land around the structure must be filled at least two feet above the regional or base flood elevation;

[2] The fill must be contiguous to land outside the floodplain; the applicant shall obtain floodplain development permit before applying for a LOMR or LOMR-F;

(c) Removal of lands from the floodplain may also occur by operation of § 87.30(1)(e), Wis. Stats., if a property owner has obtained a letter of map amendment from the federal emergency management agency under 44 CFR 70.

D. General standards applicable to all floodplain districts.

(1) Except as provided herein, no development shall be allowed in the floodplain which, acting in combination with existing or future similar works, will:

(a) Obstruct flow, defined as development which blocks the conveyance of floodwaters by itself or with other development, causing any increase in the regional flood height; or

(b) Cause any increase in the regional flood height due to floodplain storage area lost.

(2) The zoning administrator shall deny permits if it is determined the proposed development will obstruct flow or cause any increase in the regional flood height, based on the officially adopted FIRM or other adopted map, unless the provisions of § 275-22D, Floodplain amendments, are met.

(3) The County shall review all permit applications to determine whether proposed building sites will be reasonably safe from flooding and assure that all necessary permits have been received from those governmental agencies whose approval is required by federal or state law.

(a) If a proposed building site is in a flood-prone area, all new construction and substantial improvements shall be designed and anchored to prevent flotation, collapse, or lateral movement of the structure resulting from hydrodynamic and hydrostatic loads including the effects of buoyancy; be constructed with flood-resistant materials; be constructed by methods and practices to minimize flood damages; and to ensure that mechanical and utility equipment must be elevated to or above the flood protection elevation.

(b) If a subdivision or other proposed new development is in a flood-prone area the County shall assure that: such proposed subdivision or other proposed new development is consistent with the need to minimize flood damage within the flood-prone area; adequate drainage is provided to reduce exposure to flood hazards, and all public utilities and facilities, such as sewer, gas, electrical, and water systems, are located and constructed to minimize or eliminate flood damages.

(c) All subdivision proposals, including manufactured home parks, shall include regional flood elevation and floodway data for any development that meets the subdivision definition of this chapter and shall satisfy all other requirements in § 275-21D.

(4) All hydraulic and hydrologic studies shall be completed under the direct supervision of a professional engineer registered in the State of Wisconsin who shall be responsible for the technical adequacy of the study. All studies shall be reviewed and approved by the Department. Further, the applicant shall provide within such proposals regional flood elevation data and the means to provide adequate surface drainage and to minimize flood damage. Additional information, such as valley cross-sections or survey data, may be required by the Department to determine the effects of the proposal. This information shall be obtained from the applicant or the applicant's agent by the County. The provisions of § 275-17E shall apply hereto. The applicant shall provide all data and calculations for any development which would require an amendment to the district boundaries or regional flood profiles.

(a) Zone A floodplains.

[1] Hydrology. Appropriate methods shall be based on the standards in Ch. NR 116.07(3), Wis. Adm. Code, Hydrologic Analysis: Determination of Regional Flood Discharge.

[2] Hydraulic modeling. The regional flood elevation shall be based on the standards in Ch. NR 116.07(4), Wis. Adm. Code, Hydraulic Analysis: Determination of the Regional Flood Elevation, and the following:

[a] Determination of the required limits of the hydraulic model shall be based on detailed study information for downstream structures (dam, bridge, culvert) to determine adequate starting Water Surface Elevation (WSEL) for the study; and

[b] Channel sections must be surveyed; and

[c] Minimum four-foot contour data in the over banks shall be used for the development of cross-section overbank and floodplain mapping; and

[d] A maximum distance of 500 feet between cross sections is allowed in developed areas with additional intermediate cross sections required at transitions in channel bottom slope, including a survey of the channel at each location; and

[e] The most current version of Hydrologic Engineering Center's River Analysis System (HEC-RAS) shall be used; and

[f] A survey of bridge and culvert openings and the top of road is required at each structure; and

[g] Additional cross sections are required at the downstream and upstream limits of the proposed development and any necessary intermediate locations based on the length of the reach if greater than 500 feet; and

[h] Standard accepted engineering practices shall be used when assigning parameters for the base model, such as flow, Manning's N values, expansion and contraction coefficients or effective flow limits. The base model shall be calibrated to past flooding data, such as high-water marks, to determine the reasonableness of the model results. If no historical data is available, adequate justification shall be provided for any parameters outside standard accepted engineering practices; and

[i] The model must extend past the upstream limit of the difference in the existing and proposed flood profiles in order to provide a tie-in to existing studies. The height difference between the proposed flood profile and the existing study profiles shall be no more than 0.00 feet.

[3] Mapping. A work map of the reach studied shall be provided, showing all cross section locations, floodway/floodplain limits based on best available topographic data, geographic limits of the proposed development and whether the proposed development is located in the floodway.

[a] If the proposed development is located outside of the floodway, then it is determined to have no impact on the regional flood elevation; and

[b] If any part of the proposed development is in the floodway, it must be added to the base model to show the difference between existing and proposed conditions. The study must ensure that all coefficients remain the same as in the existing model, unless adequate justification based on standard accepted engineering practices is provided.

(b) Zone AE floodplains.

[1] Hydrology. If the proposed hydrology will change the existing study, the appropriate method to be used shall be based on Ch. NR 116.07(3), Wis. Adm. Code, Hydrologic Analysis: Determination of Regional Flood Discharge.

[2] Hydraulic model. The regional flood elevation shall be based on the standards in Ch. NR 116.07(4), Wis. Adm. Code, Hydraulic Analysis: Determination of the Regional Flood Elevation, and the following:

[a] Duplicate effective model. The effective model shall be reproduced to ensure correct transference of the model data and to allow integration of the revised data to provide a continuous FIS model upstream and downstream of the revised reach. If data from the effective model is available, models shall be generated that duplicate the FIS profiles and the elevations shown in the Floodway Data Table in the FIS report to within 0.1 foot; and

[b] Corrected effective model. The corrected effective model shall not include any man-made physical changes since the effective model date, but shall import the model into the most current version of HEC-RAS for Department review; and

[c] Existing (preproject conditions) model. The existing model shall be required to support conclusions about the actual impacts of the project associated with the revised (post-project) model or to establish more up-to-date models on which to base the revised (post-project) model; and

[d] Revised (post-project conditions) model. The revised (post-project conditions) model shall incorporate the existing model and any proposed changes to the topography caused by the proposed development. This model shall reflect proposed conditions; and

[e] All changes to the duplicate effective model and subsequent models must be supported by certified topographic information, bridge plans, construction plans and survey notes; and

[f] Changes to the hydraulic models shall be limited to the stream reach for which the revision is being requested. Cross sections upstream and downstream of the revised reach shall be identical to those in the effective model and result in water surface elevations and top widths computed by the revised models matching those in the effective models upstream and downstream of the revised reach, as required. The effective model shall not be truncated.

[3] Mapping. Maps and associated engineering data shall be submitted to the Department for review which meet the following conditions:

[a] Consistency between the revised hydraulic models, the revised floodplain and floodway delineations, the revised flood profiles, topographic work map, annotated FIRMs and/or Flood Boundary Floodway Maps (FBFMs), construction plans, bridge plans; and

[b] Certified topographic map of suitable scale, contour interval, and a planimetric map showing the applicable items. If a digital version of the map is available, it may be submitted in order that the FIRM may be more easily revised; and

[c] Annotated FIRM panel showing the revised 1% and 0.2% annual-chance floodplains and floodway boundaries; and

[d] If an annotated FIRM and/or FBFM and digital mapping data geographic information systems (GIS) or computer aided design and drafting (CADD) are used, then all supporting documentation or metadata must be included with the data submission along with the Universal Transverse Mercator (UTM) projection and State Plane Coordinate System in accordance with FEMA mapping specifications; and

[e] The revised floodplain boundaries shall tie into the effective floodplain boundaries; and

[f] All cross sections from the effective model shall be labeled in accordance with the effective map and a cross-section lookup table shall be included to relate to the model input numbering scheme; and

[g] Both the current and proposed floodways shall be shown on the map; and

[h] The stream center line or profile baseline used to measure stream distances in the model shall be visible on the map.

(5) Prior to any alteration or relocation of a watercourse, and prior to the issuance of any County permit which may be required for the alteration or relocation of a watercourse, the Planning and Parks Department shall notify adjacent municipalities, the appropriate regional office of the Department and the appropriate office of the Federal Emergency Management Agency, and shall require the applicant to secure all necessary state and federal permits. The standards of Subsection D must be met, and the flood-carrying capacity within the altered or relocated portion of any watercourse shall be maintained. As soon as is practical, but no later than six months after the date of the watercourse alteration or relocation, and pursuant to § 275-22, the community shall apply for a letter of map revision (LOMR) from FEMA. Any such alterations must be reviewed and approved by FEMA and the Department through the letter of map change (LOMC) process.

(6) Development which requires a permit from the Department under Chs. 30 and 31 of the Wisconsin Statutes, such as docks, piers, wharves, bridges, culverts, dams, fences and navigational aids, may be allowed, provided the necessary County permits are obtained and necessary amendments to the chapter are made according to § 275-22 of this chapter.

(7) Public or private campgrounds. Public or private campgrounds shall have a low flood damage potential and shall meet the following provisions:

(a) The campground obtains the necessary approvals from the Department of Agriculture, Trade and Consumer Protection.

(b) The campground obtains a County land use permit.

(c) The character of the river system and the campground elevation are such that a 72-hour warning of an impending flood can be given to all campground occupants.

(d) There is an adequate flood warning procedure for the campground that offers the minimum notice required under this section to all persons in the campground. This procedure shall include a written agreement between the campground owner, the County Emergency Management Coordinator and the Sheriff which specifies the flood elevation at which evacuation shall occur, personnel responsible for monitoring flood elevations, types of warning systems to be used and the procedures for notifying at-risk parties, and the methods and personnel responsible for conducting the evacuation. Written agreements referred to herein shall be for a term of not more than one year and shall be reviewed and updated at least annually in order to remain in compliance with all applicable regulations, including those of the Wisconsin Department of Agriculture, Trade and Consumer Protection and all other federal, state and local applicable regulations.

(e) Only camping units or mobile recreational vehicles, as defined in § 275-2, that are fully licensed, if required, and ready for highway use as defined in this chapter are allowed. A mobile recreational vehicle is ready for highway use if it is on its wheels or jacking system, is attached to the site only by quick-disconnect utilities and security devices and has no permanently attached additions.

(f) Camping units shall not occupy any site in the campground for more than 180 consecutive days, at which time the camping unit must be removed from the floodplain for a minimum of 24 hours.

(g) All camping units remaining on site for more than 30 days shall be issued a limited authorization by the campground operator, a written copy of which is kept on file at the campground. Such authorization shall allow placement of a camping unit, shall be for a period not to exceed 180 days and shall ensure compliance with all the provisions of this section.

(h) The County shall monitor the limited authorizations issued by the campground operator to assure compliance with the terms of this section.

(i) All camping units that remain in place for more than 180 consecutive days must meet the applicable requirements in either § 275-15, or 275-16, or 275-17, or 275-18 for the floodplain district in which the structure is located.

(j) The campground shall have signs clearly posted at all entrances warning of the flood hazard and the procedures for evacuation when a flood warning is issued.

(k) All service facilities, including but not limited to refuse collection, electrical service, natural gas lines, propane tanks, sewage systems and wells, shall be properly anchored and placed at or floodproofed to the flood protection elevation.

(8) Standards for structures in a campground:

(a) All structures must comply with § 275-14D(7) or meet the applicable requirements in §§ 275-14, 275-15 and 275-16 for the floodplain district in which the structure is located;

(b) Deck/landing. A portable landing may be allowed for a camping unit for each entry provided that the landing is not permanently attached to the ground or camping unit, is no more than 200 square feet in size, shall be portable, contain no walls or roof, and can be removed from the campground by a truck and/or trailer. Sections of such portable landings may be placed together to form a single deck not greater than 200 square feet at one entry point. Provisions for the removal of these temporary landings during flood events must be addressed within the written agreement with the municipality compliant with § 275-14D(7). Any such deck/landing structure may be constructed at elevations lower than the flood protection elevation but must not obstruct flow of flood waters or cause any increase in flood levels during the occurrence of the regional flood.

(c) Decks/patios that are constructed completely at grade may be allowed but must also comply with applicable shoreland zoning standards.

(d) Camping equipment and appurtenant equipment in the campground may be allowed provided that the equipment is not permanently attached to the ground or camping unit, is not used as a habitable structure, and must not obstruct flow of flood waters or cause any increase in flood levels during the occurrence of the regional flood. Provisions for the removal of this equipment during flooding events shall be addressed within the written agreement with the municipality compliant with Subsection D(7)(d).

(e) Once a flood warning in the written agreement has been issued for the campground, the campground owner or the designated operator shall ensure that all persons, camping units, decks, camping equipment and appurtenant equipment in the campground shall be evacuated within the timelines specified within the written agreement with the municipality compliant with § 275-14D(7).

(9) A land use permit shall be obtained as provided in §§ 275-21C and 275-14D before any development; repair, modification, or addition to an existing structure; or change in the use of a building or structure, including sewer and water facilities, may be initiated.

§ 275-15 Floodway District (FW).

A. Applicability. This section applies to all floodway areas on the floodplain zoning maps and those identified pursuant to § 275-17E.

B. Permitted uses. The following open space uses are allowed in the Floodway District and the floodway areas of the General Floodplain District, if: they are not prohibited by any other ordinance; they meet the standards in § 275-15C and D; and all permits or certificates have been issued according to § 275-21.

(1) Agricultural uses, such as: farming, outdoor plant nurseries, horticulture, viticulture and wild crop harvesting.

(2) Nonstructural industrial and commercial uses, such as loading areas, parking areas and airport landing strips.

(3) Nonstructural recreational uses, such as golf courses, tennis courts, archery ranges, picnic grounds, boat ramps, swimming areas, parks, wildlife and nature preserves, game farms, fish hatcheries, shooting, trap and skeet activities, hunting and fishing areas and hiking and horseback riding trails, subject to the fill limitations of § 275-15C(4).

(4) Uses or structures accessory to open space uses or classified as historic structures that comply with § 275-15C and D.

(5) Extraction of sand, gravel or other materials that comply with § 275-15C(4).

(6) Functionally water dependent uses, such as docks, piers or wharves, dams, flowage areas, culverts, navigational aids and river crossings of transmission lines, and pipelines that comply with Chs. 30 and 31, Wis. Stats.

(7) Public utilities, streets and bridges that comply with § 275-15C(3).

(8) Portable latrines that are removed prior to flooding and systems associated with recreational areas and Department-approved campgrounds that meet the applicable provisions of local ordinances and Ch. SPS 383, Wis. Adm. Code.

(9) Public or private wells used to obtain potable water for recreational areas that meet the requirements of local ordinances and Chs. NR 811 and NR 812, Wis. Adm. Code.

(10) Wastewater treatment ponds or facilities permitted under § NR 110.15(3)(b), Wis. Adm. Code.

(11) Sanitary sewer or water supply lines to service existing or proposed development located outside the floodway that complies with the regulations for the floodplain area occupied.

C. Standards for development in the floodway.

(1) General.

(a) Any development in the floodway shall comply with § 275-14D and have a low flood damage potential.

(b) Applicants shall provide an analysis calculating the effects of this proposal on the regional flood height to determine the effects of the proposal according to § 275-14D(1) and (4). The analysis must be completed by a registered professional engineer in the state of Wisconsin.

(c) Any encroachment in the regulatory floodway is prohibited unless the data submitted for § 275-15C(1)(b) above demonstrates that the encroachment will cause no increase in flood elevations in flood events up to the base flood at any location or removes the encroached area from the regulatory floodway as provided in § 275-14C(4).

(2) Structures. Structures accessory to permanent open space uses, including utility and sanitary facilities, or functionally dependent on a waterfront location may be allowed by permit if the structures comply with the following criteria:

(a) Not designed for human habitation, does not have a high flood damage potential and is constructed to minimize flood damage;

(b) Shall either have the lowest floor elevated to or above the flood protection elevation or shall meet all the following standards:

[1] Have the lowest floor elevated to or above the regional flood elevation and be dry floodproofed so that the structure is watertight with walls substantially impermeable to the passage of water and completely dry to the flood protection elevation without human intervention during flooding;

[2] Have structural components capable of meeting all provisions of § 275-15C(2)(g) and;

[3] Be certified by a registered professional engineer or architect, through the use of a Federal Emergency Management Agency Floodproofing Certificate, that the design and methods of construction are in accordance with § 275-15C(2)(g).

(c) Must be anchored to resist flotation, collapse, and lateral movement;

(d) Mechanical and utility equipment must be elevated to or above the flood protection elevation; and

(e) Must not obstruct flow of floodwaters or cause any increase in flood levels during the occurrence of the regional flood.

(f) For a structure designed to allow the automatic entry of floodwaters below the regional flood elevation, the applicant shall submit a plan that meets § 275-15C(2)(a) through (e) and meets or exceeds the following standards:

[1] The lowest floor must be elevated to or above the regional flood elevation;

[2] A minimum of two openings having a total net area of not less than one square inch for every square foot of enclosed area subject to flooding;

[3] The bottom of all openings shall be no higher than one foot above the lowest adjacent grade; openings may be equipped with screens, louvers, valves, or other coverings or devices provided that they permit the automatic entry and exit of floodwaters, otherwise must remain open.

[4] The use must be limited to parking, building access or limited storage.

(g) Certification. Whenever floodproofing measures are required, a registered professional engineer or architect shall certify that the following floodproofing measures will be utilized, where appropriate, and are adequate to withstand the flood depths, pressures, velocities, impact and uplift forces and other factors associated with the regional flood:

[1] Reinforcement of floors and walls to resist rupture, collapse, or lateral movement caused by water pressures or debris buildup;

[2] Construction of wells, water supply systems and waste treatment systems so as to prevent the entrance of flood waters in such systems and must be in accordance with provisions in § 275-15D(4) and (5);

[3] Subsurface drainage systems to relieve external pressures on foundation walls and basement floors;

[4] Cutoff valves on sewer lines or the elimination of gravity flow basement drains; and

[5] Placement of utilities to or above the flood protection elevation.

(3) Public utilities, streets and bridges may be allowed by permit, if:

(a) Adequate floodproofing measures are provided to the flood protection elevation; and

(b) Construction meets the development standards of § 275-14D(4).

(4) Fills or deposition of materials may be allowed by permit, if:

(a) The requirements of § 275-14D(1) are met;

(b) No material is deposited in navigable waters unless a permit is issued by the Department pursuant to Ch. 30, Wis. Stats., and a permit pursuant to § 404 of the Federal Water Pollution Control Act, Amendments of 1972, 33 U.S.C. § 1344 has been issued, if applicable, and all other requirements have been met;

(c) The fill or other materials will be protected against erosion by riprap, vegetative cover, sheet piling or bulkheading; and

(d) The fill is not classified as a solid or hazardous material.

D. Prohibited uses. All uses not listed as permitted uses in § 275-15B are prohibited, including the following uses:

(1) Habitable structures, structures with high flood damage potential, or those not associated with permanent open space uses;

(2) Storing materials that are buoyant, flammable, explosive, injurious to property, water quality, or human, animal, plant, fish or other aquatic life;

(3) Uses not in harmony with or detrimental to uses permitted in the adjoining districts;

(4) Any private or public sewage systems, except portable latrines that are removed prior to flooding and systems associated with recreational areas and Department-approved campgrounds that meet the applicable provisions of local ordinances and Ch. SPS 383, Wis. Adm. Code;

(5) Any public or private wells which are used to obtain potable water, except those for recreational areas that meet the requirements of local ordinances and Chs. NR 811 and NR 812, Wis. Adm. Code;

(6) Any solid or hazardous waste disposal sites;

(7) Any wastewater treatment ponds or facilities, except those permitted under § NR 110.15(3)(b), Wis. Adm. Code; and

(8) Any sanitary sewer or water supply lines, except those to service existing or proposed development located outside the floodway which complies with the regulations for the floodplain area occupied.

§ 275-16 Floodfringe District (FF).

A. Applicability. This section applies to all floodfringe areas shown on the floodplain zoning maps and those identified pursuant to § 275-17E.

B. Permitted uses. Any structure, land use, or development is allowed in the Floodfringe District if the standards in § 275-16C are met, the use is not prohibited by this or any other ordinance or regulation and all permits or certificates specified in § 275-21 have been issued.

C. Standards for development in the floodfringe. Section 275-14D shall apply in addition to the following requirements according to the use requested. Any existing structure in the floodfringe must meet the requirements of § 275-19, Nonconforming uses:

(1) Residential uses. Any structure, including a manufactured home, which is to be newly constructed or moved into the floodfringe, shall meet or exceed the following standards.

(a) All new construction, including placement of manufactured homes, and substantial improvement of residential structures, shall have the lowest floor elevated to or above the flood protection elevation on fill. The fill around the structure shall be one foot or more above the regional flood elevation extending at least 15 feet beyond the limits of the structure. No area may be removed from the floodfringe district unless it can be shown to meet § 275-14C(5).

(b) Notwithstanding § 275-16C(1)(a), a basement or crawlspace floor may be placed at the regional flood elevation if the basement or crawlspace is designed to make all portions of the structure below the flood protection elevation watertight with walls substantially impermeable to the passage of water and with structural components having the capability of resisting hydrostatic and hydrodynamic loads and effects of buoyancy. No floor of any kind is allowed below the regional flood elevation;

(c) Contiguous dryland access shall be provided from a structure to land outside of the floodplain, except as provided in Subsection C(1)(d).

(d) In developments where existing street or sewer line elevations make compliance with Subsection C(1)(c) impractical, the municipality may permit new development and substantial improvements where roads are below the regional flood elevation, if:

[1] The municipality has written assurance from police, fire and emergency services that rescue and relief will be provided to the structure(s) by wheeled vehicles during a regional flood event; or

[2] The municipality has a DNR-approved emergency evacuation plan that follows acceptable hazard mitigation planning guidelines.

(2) Accessory structures or uses. In addition to § 275-14D, new construction and substantial improvements of accessory structures shall be constructed on fill with the lowest floor at or above the regional flood elevation.

(3) Commercial uses. In addition to § 275-14D, any commercial structure which is erected, altered or moved into the floodfringe shall meet the requirements of § 275-16C(1). Subject to the requirements of § 275-16C(5), storage yards, surface parking lots and other such uses may be placed at lower elevations if an adequate warning system exists to protect life and property.

(4) Manufacturing and industrial uses. In addition to § 275-14D, any manufacturing or industrial structure which is erected, altered or moved into the floodfringe shall have the lowest floor elevated to or above the flood protection elevation or meet the floodproofing standards in § 275-20. Subject to the requirements of § 275-16C(5), storage yards, surface parking lots and other such uses may be placed at lower elevations if an adequate warning system exists to protect life and property.

(5) Storage of materials. Materials that are buoyant, flammable, explosive, or injurious to property, water quality or human, animal, plant, fish or aquatic life shall be stored at or above the flood protection elevation or floodproofed in compliance with § 275-20. Adequate measures shall be taken to ensure that such materials will not enter the water body during flooding.

(6) Public utilities, streets and bridges. All utilities, streets and bridges shall be designed to be compatible with comprehensive floodplain development plans; and

(a) When failure of public utilities, streets and bridges would endanger public health or safety, or where such facilities are deemed essential, construction or repair of such facilities shall only be permitted if they are designed to comply with § 275-20.

(b) Minor roads or nonessential utilities may be constructed at lower elevations if they are designed to withstand flood forces to the regional flood elevation.

(7) Sewage systems. All sewage disposal systems shall be designed to minimize or eliminate infiltration of flood water into the system, pursuant to § 275-20C, to the flood protection elevation and meet the provisions of all local ordinances and Ch. SPS 383, Wis. Adm. Code.

(8) Wells. All wells shall be designed to minimize or eliminate infiltration of floodwaters into the system, pursuant to § 275-20C, to the flood protection elevation and shall meet the provisions of Chs. NR 811 and NR 812, Wis. Adm. Code.

(9) Solid waste disposal sites. Disposal of solid or hazardous waste is prohibited in floodfringe areas.

(10) Deposition of materials. Any deposited material must meet all the provisions of this article.

(11) Manufactured homes.

(a) Owners or operators of all manufactured home parks and subdivisions shall provide adequate surface drainage to minimize flood damage, and prepare, secure approval and file an evacuation plan, indicating vehicular access and escape routes, with local emergency management authorities.

(b) In existing manufactured home parks, all new homes, replacement homes on existing pads, and substantially improved homes shall:

[1] Have the lowest floor elevated to the flood protection elevation; and

[2] Be anchored so they do not float, collapse or move laterally during a flood.

(c) Outside of existing manufactured home parks, including new manufactured home parks and all single units outside of existing parks, all new, replacement and substantially improved manufactured homes shall meet the residential development standards for the floodfringe in § 275-16C(1)(b) and (c).

(12) Mobile recreational vehicles. All mobile recreational vehicles must be on site for less than 180 consecutive days and be either:

(a) Fully licensed and ready for highway use; or

(b) Shall meet the elevation and anchoring requirements in § 275-16C(11)(b) and (c). A mobile recreational vehicle is ready for highway use if it is on its wheels or jacking system, is attached to the site only by quick-disconnect utilities and security devices and has no permanently attached additions.

§ 275-17 General Floodplain District.

A. Applicability. The provisions for the General Floodplain District shall apply to development in all floodplains mapped as A, AO, AH, and in AE Zones within which a floodway is not delineated on the Flood Insurance Rate Maps identified in § 275-14C(1).

B. Floodway boundaries. For proposed development in Zone A, or in Zone AE within which a floodway is not delineated on the Flood Insurance Rate Map identified in § 275-14C(1), the boundaries of the regulatory floodway shall be determined pursuant to § 275-17E. If the development is proposed to encroach upon the regulatory floodway, the development is subject to the standards of § 275-15. If the development is located entirely within the floodfringe, the development is subject to the standards of § 275-16.

C. Permitted uses. Pursuant to § 275-17E it shall be determined whether the proposed use is located within the floodway or floodfringe. Those uses permitted in the Floodway (§ 275-15B) and Floodfringe (§ 275-16B) Districts are allowed within the General Floodplain District, according to the standards of § 275-17D provided that all permits or certificates required under § 275-21 have been issued.

D. Standards for development in the general floodplain district. Section 275-15 applies to floodway areas, determined to pursuant to § 275-17E; Section 275-16 applies to floodfringe areas, determined to pursuant to § 275-17E.

(1) New construction and substantial improvement of structures in Zone AO shall have the lowest floor, including basement, elevated:

(a) To or above the depth, in feet, as shown on the FIRM above the highest adjacent natural grade; or

(b) If the depth is not specified on the FIRM, to or above two feet above the highest adjacent natural grade.

(2) New construction and substantial improvement of structures in Zone AH shall have the lowest floor, including basement, elevated to or above the flood protection elevation.

(3) In AO/AH Zones, provide adequate drainage paths to guide floodwaters around structures.

(4) All development in Zone AO and Zone AH shall meet the requirements of § 275-16 applicable to floodfringe areas.

E. Determining floodway and floodfringe limits. Upon receiving an application for development within Zone A, or within Zone AE where a floodway has not been delineated on the Flood Insurance Rate Maps, the zoning administrator shall:

(1) Require the applicant to submit two copies of an aerial photograph or a plan which shows the proposed development with respect to the general floodplain district limits, stream channel, and existing floodplain developments, along with a legal description of the property, fill limits and elevations, building floor elevations and flood proofing measures; and the flood zone as shown on the FIRM.

(2) Require the applicant to furnish any of the following information deemed necessary by the Department to evaluate the effects of the proposal upon flood height and flood flows, regional flood elevation and to determine floodway boundaries.

(a) A hydrologic and hydraulic study as specified in § 275-14D(4).

(b) Plan (surface view) showing elevations or contours of the ground; pertinent structure, fill or storage elevations; size, location and layout of all proposed and existing structures on the site; location and elevations of streets, water supply, and sanitary facilities; soil types and other pertinent information;

(c) Specifications for building construction and materials, floodproofing, filling, dredging, channel improvement, storage, water supply and sanitary facilities.

§ 275-18 Flood Storage District.

A. Applicability. The provisions of this section apply to all areas within the Flood Storage District as defined in § 275-2 and shown on the Official Floodplain Zoning Maps.

B. Purpose. The Flood Storage District protects flood storage areas and requires that any development in the storage area will not decrease the effective flood storage capacity which would cause higher flood elevation.

C. Permitted uses. Permitted uses or developments in the Floodfringe District § 275-16C are permitted in the Flood Storage District; provided, however, that the standards of Subsection D are also met.

D. Standards for development in flood storage districts.

(1) Development in a Flood Storage District shall not cause an increase equal to or greater than 0.00 foot in the height of the regional flood.

(2) No development shall be allowed which removes flood storage volume unless an equal volume of storage as defined by the pre-development ground surface and the regional flood elevation shall be provided in the immediate area of the proposed development to compensate for the volume of storage, which is lost (compensatory storage). Excavation below the groundwater table is not considered to provide an equal volume of storage.

(3) If compensatory storage cannot be provided, the area may not be used or developed unless the entire area is rezoned to a floodfringe district, including revisions to the floodplain study and a map amendment.

(4) No area may be removed from the Flood Storage District unless it can be shown that the area has been filled to the flood protection elevation and is contiguous to lands lying outside of the floodplain.

§ 275-19 Nonconforming uses and structures; floodplain.

A. General provisions and Applicability.

(1) The standards in this section shall apply to all uses and buildings that do not conform to the provisions contained within a floodplain zoning ordinance or with § 87.30, Wis. Stats. and §§ NR 116.12 through 14, Wis. Adm. Code and 44 CFR 59 through 72. These standards shall apply to all modifications or additions to any nonconforming use or structure and to the use of any structure or premises which was lawful before the passage of this chapter or any amendment thereto. A party asserting existence of a lawfully established nonconforming use or structure has the burden of proving that the use or structure was compliant with the floodplain zoning ordinance in effect at the time the use or structure was created.

(2) As permit applications are received for additions, modifications, or substantial improvements to nonconforming buildings in the floodplain, the County shall develop a list of those nonconforming buildings, their present equalized assessed value, and a list of the costs of those activities associated with changes to those buildings.

(3) No modifications or additions to a nonconforming use or structure shall be permitted unless it is brought into compliance with this chapter. Modifications or additions include but are not limited to any alteration, addition, modification, structural repair, rebuilding or replacement of any such existing use, structure or ancillary structure or use. Maintenance is not considered a modification; this includes painting, decorating, paneling and other nonstructural components and the maintenance, repair or replacement of existing private sewage or water supply systems or connections to public utilities. Any costs associated with the repair of damaged structures are not considered maintenance.

(4) If a nonconforming use or structure, permanent or temporary, is discontinued for 12 consecutive months, it is no longer permitted, and any future use of the property, and any structure thereon, shall be made to conform to the applicable requirements of this chapter. Conformance may include moving the structure.

(5) The construction of a deck that does not exceed 200 square feet and that is adjacent to the exterior wall of a principal structure is not an extension, modification or addition. The roof of a structure may extend over a portion of the deck in order to provide safe ingress or egress to the principal structure.

(6) As requests are received for modifications or additions to nonconforming uses or nonconforming structures, a record shall be kept which lists the nonconforming uses and nonconforming structures, the present equalized assessed value, the cost of those additions or modifications which have been permitted and the percentage of the structure's total current value represented by modifications.

(7) No modification or addition to any nonconforming structure or any structure with a nonconforming use, which over the life of the structure would equal or exceed 50% of its present equalized assessed value, shall be allowed unless the entire structure is permanently changed to a conforming structure with a conforming use in compliance with the applicable requirements of this chapter. Contiguous dry-land access must be provided for residential and commercial uses in compliance with § 275-16C. The costs of elevating the lowest floor of a nonconforming building or a building with a nonconforming use to the flood protection elevation are excluded from the 50% provisions of this subsection. No modifications or additions to a nonconforming use or structure shall be permitted unless they comply with this chapter. The words "modification" and "addition" include, but are not limited to, any alteration, addition, modification, structural repair, rebuilding or replacement of any such existing use, structure or accessory structure or use. Maintenance is not considered a modification; this includes painting, decorating, paneling and other nonstructural components and the maintenance, repair or replacement of existing private sewage or water supply systems or connections to public utilities. Any costs associated with the repair of a damaged structure are not considered maintenance.

(8) No maintenance to any nonconforming structure or any structure with a nonconforming use, the cost of which would equal or exceed 50% of its present equalized assessed value, shall be allowed unless the entire structure is permanently changed to a conforming structure with a conforming use in compliance with the applicable requirements of this chapter. Contiguous dry-land access must be provided for residential and commercial uses in compliance with § 275-16C. Maintenance to any nonconforming structure, which does not exceed 50% of its present equalized assessed value on a per-event basis, does not count against the cumulative calculations over the life of the structure for substantial improvement calculations.

(9) If, on a per-event basis, the total value of the work being done under Subsection A(6) and (7) equals or exceeds 50% of the present equalized assessed value, the work shall not be permitted unless the entire structure is permanently changed to a conforming structure with a conforming use in compliance with the applicable requirements of this chapter. Contiguous dry-land access must be provided for residential and commercial uses in compliance with § 275-16C.

(10) Except as provided in Subsection A(11), if any nonconforming structure or any structure with a nonconforming use is destroyed or is substantially damaged, it cannot be replaced, reconstructed or rebuilt unless the use and the structure meet the current ordinance requirements. A structure is considered substantially damaged if the total cost to restore the structure to its predamaged condition equals or exceeds 50% of the structure's present equalized assessed value.

(11) For nonconforming buildings that are substantially damaged or destroyed by a nonflood disaster, the repair or reconstruction of any such nonconforming building shall be permitted in order to restore it to the size and use in effect prior to the damage event, provided that the minimum federal code requirements below are met and all required permits have been granted prior to the start of construction.

(a) Residential structures:

[1] Shall have the lowest floor, including basement, elevated to or above the base flood elevation using fill, pilings, columns, posts or perimeter walls. Perimeter walls must meet the requirements of § 275-20C.

[2] Shall be anchored to prevent flotation, collapse, or lateral movement of the structure resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy, and shall be constructed with methods and materials resistant to flood damage.

[3] Shall be constructed with electrical, heating, ventilation, plumbing and air-conditioning equipment and other service facilities that are designed and/or elevated so as to prevent water from entering or accumulating within the components during conditions of flooding.

[4] In A Zones, obtain, review and utilize any flood data available from a federal, state or other source.

[5] In AO Zones with no elevations specified, shall have the lowest floor, including basement, meet the standards in § 275-16C.

[6] In AO Zones, shall have adequate drainage paths around structures on slopes to guide floodwaters around and away from the structure.

(b) Nonresidential structures.

[1] Shall meet the requirements of § 275-19A(11)(a)[1], [2], [5] and [6].

[2] Shall either have the lowest floor, including basement, elevated to or above the regional flood elevation; or together with attendant utility and sanitary facilities, shall meet the standards in § 275-20A and B.

[3] In AO Zones with no elevations specified, shall have the lowest floor, including basement, meet the standards in § 275-16C.

(12) Historic structures. A nonconforming historic structure may be altered if the alteration will not preclude the structure's continued designation as an historic structure, the alteration will comply with § 275-15C, flood-resistant materials are used, and construction practices and floodproofing methods that comply with § 275-20 are used. Repair or rehabilitation of historic structures shall be exempt from the development standards of § 275-19A(11)(a) if it is determined that the proposed repair or rehabilitation will not preclude the structure's continued designation as an historic structure and is the minimum necessary to preserve the historic character and design of the structure.

(13) Notwithstanding anything in this chapter to the contrary, modifications, additions, maintenance, and repairs to a nonconforming building shall not be prohibited based on cost and the building's nonconforming use shall be permitted to continue if:

(a) Any living quarters in the nonconforming building are elevated to be at or above the flood protection elevation;

(b) The lowest floor of the nonconforming building, including the basement, is elevated to or above the regional flood elevation;

(c) The nonconforming building is permanently changed to conform to the applicable requirements of § 275-14D; and

(d) If the nonconforming building is in the floodway, the building is permanently changed to conform to the applicable requirements of §§ 275-15C(1), (b) through (e), (3), (4) and 275-19B. Any development that adds additional fill or creates an encroachment in the floodplain from beyond the original nonconforming structure's 3-D building envelope must determine the floodway in accordance with § 275-15. If the encroachment is in the floodway, it must meet the standards in § 275-15C(4); or

(e) If the nonconforming building is in the floodfringe, the building is permanently changed to conform to the applicable requirements of §§ 275-16C and 275-19C; the building will remain nonconforming.

(f) Repair or reconstruction of nonconforming structures and substantial improvements of residential buildings in Zones A1-30, AE, and AH must have the lowest floor (including basement) elevated to or above the base flood elevation.

(g) Repair or reconstruction of nonconforming structures and substantial improvements of nonresidential buildings in Zones A1-30, AE, and AH must have the lowest floor (including basement) elevated to or above the base flood elevation, or (together with attendant utility and sanitary facilities) be designed so that below the base flood elevation the building is watertight with walls substantially impermeable to the passage of water and with structural components capable of resisting hydrostatic and hydrodynamic loads and effects of buoyancy.

[1] Where a nonresidential structure is intended to be made watertight below the base flood elevation, a registered professional engineer or architect must develop and/or review structural design, specifications, and plans for the construction, and must certify that the design and methods of construction are in accordance with accepted standards of practice for meeting the provisions of § 275-19A(13)(g) above.

[2] The community must maintain a record of such certification including the specific elevation to which each such structure is floodproofed.

(h) Fully enclosed areas below the lowest floor of repair or reconstruction of nonconforming structures and substantial improvements in Zones A1-30, AE, and AH that are usable solely for parking of vehicles, building access, or storage, must be designed to adequately equalize hydrostatic forces on exterior walls by allowing for the entry and exit of floodwaters. Subsequent improvements to repaired or reconstructed nonconforming structures must not increase the degree of their nonconformity. Designs for meeting this requirement must either be certified by a registered professional engineer or architect, or meet the following criteria:

[1] A minimum of two openings into each enclosed area must be located below the base flood elevation and provide a total net area of not less than one square inch for every square foot of enclosed area;

[2] The bottom of all openings must be no higher than one foot above the adjacent grade;

[3] Openings may be equipped with screens, louvers, valves, or other coverings if they permit the automatic entry and exit of floodwaters.

(i) Manufactured homes that are placed or substantially improved within Zones A1-30, AE, and AH outside of a manufactured home park or subdivision, in a new manufactured home park or subdivision, in an expansion to an existing manufactured home park or subdivision, or in an existing manufactured home park or subdivision on which a manufactured home has incurred substantial damage as a result of flood, must be elevated on a permanent foundation such that the lowest floor of the manufactured home is at or above the base flood elevation, and be securely anchored to an adequately anchored foundation system to resist flotation, collapse, and lateral movement.

(j) Manufactured homes that are placed or substantially improved within Zones A1-30, AE, and AH on existing sites in an existing manufactured home park that is not undergoing expansion and on which a manufactured home has not incurred substantial damage as a result of flood must be elevated so that either the lowest floor of the manufactured home is at or above the base flood elevation, or 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, and be securely anchored to an adequately anchored foundation system to resist flotation, collapse, and lateral movement.

(k) Recreational vehicles placed on sites within Zones A1-30, AH, and AE must either:

[1] Be on site for fewer than 180 consecutive days; or

[2] Be fully licensed and ready for highway use (a recreational vehicle is ready for highway use if it is on its wheels or jacking system, is attached to the site only by quick-disconnect type utilities and security devices, and has no permanently attached additions); or

[3] Meet the elevation and anchoring requirements for manufactured homes in § 275-19A(13)(i) above.

(l) In a regulatory floodway that has been delineated on the FIRM in Zone A1-30 or AE, encroachments, including repair or reconstruction of nonconforming structures, substantial improvement, or other development (including fill) must be prohibited unless it has been demonstrated through hydrologic and hydraulic analyses performed in accordance with standard engineering practice that the proposed encroachment will not result in any increase in flood levels within the community during the occurrence of the base flood discharge. Subsequent improvements to repaired or reconstructed nonconforming structures must not increase the degree of their nonconformity;

(m) In Zone A, the community must obtain, review, and reasonably utilize any base flood elevation and floodway data available from a federal, state, or other source as criteria for requiring repair or reconstruction of nonconforming structures, substantial improvement, and other development to meet § 275-19A(13)(f) through (l) (inclusive) above. Any development that adds additional fill or creates an encroachment in the floodplain from beyond the original nonconforming structure's 3-D building envelope must determine the floodway in accordance with § 275-15. If the encroachment is in the floodway, it must meet the standards in § 275-15C(4). Subsequent improvements to repair or reconstructed nonconforming structures must not increase the degree of their nonconformity;

(n) In Zones A1-30 or AE where a regulatory floodway has not been delineated on the FIRM, repair or reconstruction of nonconforming structures, substantial improvement, or other development that adds additional fill or creates an encroachment in the floodplain from beyond the original nonconforming structure's 3-D building envelope must determine the floodway in accordance with § 275-15. If the encroachment is in the floodway, it must meet the standards in § 275-15C(4) Subsequent improvements to repair or reconstructed nonconforming structures must not increase the degree of their nonconformity;

(o) Notwithstanding the requirements of § 275-19A(13)(l) and (n) above, the community may permit certain development in Zones A1-30 and AE where a floodway has not been delineated, which will increase the water surface elevation of the base flood by more than one foot, or in a regulatory floodway, which will result in an increase in base flood elevations, if the community first obtains a Conditional Letter of Map Revision (CLOMR) from FEMA and fulfills the requirements of 44 CFR 65.12.

(p) In Zone AO, repair or reconstruction of nonconforming structures and substantial improvements of residential structures must have the lowest floor (including basement) elevated above the highest adjacent grade at least as high as the depth number specified in feet on the FIRM (at least two feet if no depth number is specified). Subsequent improvements to repair or reconstructed nonconforming structures must not increase the degree of their nonconformity; or

(q) In Zone AO, repair or reconstruction of nonconforming structures and substantial improvements of nonresidential structures must have the lowest floor (including basement) elevated above the highest adjacent grade at least as high as the depth number specified in feet on the FIRM (at least two feet if no depth number is specified), or (together with attendant utility and sanitary facilities) be structurally dry-floodproofed to that level according to the standard specified in § 275-19A(13)(g) above. Subsequent improvements to repair or reconstructed nonconforming structures must not increase the degree of their nonconformity.

(14) Uses or structures which are deemed nuisances by a court of competent jurisdiction shall not be allowed to continue as nonconforming uses.

B. Floodway District.

(1) No modification or addition shall be allowed to any nonconforming structure or any structure with a nonconforming use in the Floodway District, unless such modification or addition:

(a) Has been granted a permit or variance which meets all ordinance requirements;

(b) Meets the requirements of § 275-19A;

(c) Shall not increase the obstruction to flood flows or regional flood height;

(2) Any addition to the existing structure shall be floodproofed, pursuant to § 275-20, by means other than the use of fill, to the flood protection elevation; and

(3) If any part of the foundation below the flood protection elevation is enclosed, the following standards shall apply:

(a) The enclosed area shall be designed by a registered architect or engineer to allow for the efficient entry and exit of floodwaters without human intervention. A minimum of two openings must be provided with a minimum net area of at least one square inch for every one square foot of the enclosed area. The lowest part of the opening can be no more than 12 inches above the adjacent grade;

(b) The parts of the foundation located below the flood protection elevation must be constructed of flood-resistant materials; and

(c) Mechanical and utility equipment must be elevated or floodproofed to or above the flood protection elevation; and

(d) The use must be limited to parking, building access or limited storage.

(4) No new on-site sewage disposal system, or addition to an existing on-site sewage disposal system, except where an addition has been ordered by a government agency to correct a hazard to public health, shall be allowed in the Floodway District. Any replacement, repair or maintenance of an existing on-site sewage disposal system in a floodway area shall meet the applicable requirements of Chapter 190, Private On-Site Wastewater Treatment Systems, of the Code of Washington County and Ch. SPS 383, Wis. Adm. Code.

(5) No new well or modification to an existing well used to obtain potable water shall be allowed in the Floodway District. Any replacement, repair or maintenance of an existing well in the Floodway District shall meet the applicable requirements of Chs. NR 811 and NR 812, Wis. Adm. Code.

C. Floodfringe District.

(1) No modification or addition shall be allowed to any nonconforming structure or any structure with a nonconforming use unless such modification or addition has been granted a permit or variance by the municipality and meets the requirements of § 275-16, except where § 275-19C(2) is applicable.

(2) Where compliance with the provisions of Subsection C(1) would result in unnecessary hardship and only where the structure will not be used for human habitation or be associated with a high flood damage potential, the Board of Adjustment, using the procedures established in § 275-21F, may grant a variance from those provisions of Subsection C(1) for modifications or additions using criteria listed below. Modifications or additions which are protected to elevations lower than the flood protection elevation may be permitted if:

(a) No floor is allowed below the regional flood elevation for residential or commercial structures;

(b) Human lives are not endangered;

(c) Public facilities, such as water or sewer, shall not be installed;

(d) Flood depths shall not exceed two feet;

(e) Flood velocities shall not exceed two feet per second; and

(f) The structure shall not be used for storage of materials as described in § 275-16C(5).

(3) All new private sewage disposal systems, or addition to, replacement, repair or maintenance of a private sewage disposal system shall meet all the applicable provisions of all local ordinances, § 275-20C and Ch. SPS 383, Wis. Adm. Code.

(4) All new wells, or addition to replacement, repair or maintenance of a well, shall meet the applicable provisions of this chapter, § 275-20C and Chs. NR 811 and NR 812, Wis. Adm. Code.

D. (Reserved)

E. Flood Storage District. No modifications or additions shall be allowed to any nonconforming structures or uses in a Flood Storage District unless the standards set forth in § 275-18D are met.

§ 275-20 Floodproofing standards for nonconforming structures or uses.

A. No permit or variance shall be issued for a nonresidential structure designed to be watertight below the regional flood elevation until the applicant submits a plan certified by a registered professional engineer or architect that the floodproofing measures will protect the structure or development to the flood protection elevation and submits a FEMA Floodproofing Certificate. Floodproofing is not an alternative to the development standards in § 275-14; § 275-15; § 275-16; and/or § 275-17.

B. For a structure designed to allow the entry of floodwaters, no permit or variance shall be issued until the applicant submits a plan either:

(1) Certified by a registered professional engineer or architect; or

(2) Meets or exceeds the following standards:

(a) A minimum of two openings having a total net area of not less than one square inch for every square foot of enclosed area subject to flooding;

(b) The bottom of all openings shall be no higher than one foot above grade; and

(c) Openings may be equipped with screens, louvers, valves, or other coverings or devices, provided that they permit the automatic entry and exit of floodwaters.

C. Floodproofing measures shall be designed, as appropriate, to:

(1) Withstand flood pressures, depths, velocities, uplift and impact forces and other regional flood factors;

(2) Protect structures to the flood protection elevation;

(3) Anchor structures to foundations to resist flotation and lateral movement;

(4) Minimize or eliminate infiltration of floodwaters;

(5) Minimize or eliminate discharges into floodwaters.

(6) Placement of essential utilities to or above the flood protection elevation; and

(7) If any part of the foundation below the flood protection elevation is enclosed, the following standards shall apply:

(a) The enclosed area shall be designed by a registered architect or engineer to allow for the efficient entry and exit of floodwaters without human intervention. A minimum of two openings must be provided with a minimum net area of at least one square inch for every one square foot of the enclosed area. The lowest part of the opening can be no more than 12 inches above the adjacent grade;

(b) The parts of the foundation located below the flood protection elevation must be constructed of flood-resistant materials;

(c) Mechanical and utility equipment must be elevated or floodproofed to or above the flood protection elevation; and

(d) The use must be limited to parking, building access or limited storage.