Skip to main content
Loading…
This section is included in your selections.

Click here to view prior versions of this section.

A. Designation. Designated or potential Geologic Hazard Areas include Landslide, Seismic, and Erosion Hazard Areas. With the exception of bank erosion hazard areas and fault rupture hazard areas, their potential locations are shown on maps available from the planning official. Final designations shall be based on site conditions and other available data or information [See VMC 20.740.020(C)(1)].

1. Landslide Hazard Areas. Potential landslide hazard areas are identified from the sources listed below.

a. Slopes greater than 25% on the property and adjacent areas within 100 feet, except engineered slopes such as cut and fill slopes along transportation routes (including trails), railroad and other berms, or dikes.

b. Areas of historic or active landslides, potential instability, or older landslide debris identified on the 1975 map by Allen Fiksdal of the Washington State Department of Natural Resources entitled, Slope Stability: Clark County Washington as revised or superseded, or identified from other available data or in the field by a qualified professional and adjacent areas within 100 feet.

2. Seismic Hazard Areas. Seismic Hazard Areas include Liquefaction or Dynamic Settlement, Ground Shaking Amplification, and Fault Rupture Hazard Areas.

a. Liquefaction or Dynamic Settlement. The following are designated Liquefaction or Dynamic Settlement Hazard Areas:

1. Areas with Low to Moderate, Moderate, Moderate to High, or High liquefaction susceptibility or Peat Deposits as indicated on the Alternative Liquefaction Susceptibility Map of Clark County, Washington based on Swanson’s Groundwater Model by Stephen P. Palmer, Sammantha L. Magsino, James L. Poelstra, and Rebecca A. Niggemann, September, 2004, as revised or superseded.

2. Areas of fill (Fn) identified by the 1972 USDA Soil Conservation Service Soil Survey of Clark County Washington and by the planning official, based on other reliable evidence.

b. Ground Shaking Amplification. The following are designated Ground Shaking Amplification Hazard Areas:

Site Classes C to D, D, D to E, E and F as indicated on the Site Class Map of Clark County, Washington by Stephen P. Palmer, Sammantha L. Magsino, James L. Poelstra, and Rebecca A. Niggemann, September, 2004 as revised or superseded.

c. Fault Rupture Hazard Areas. Potential Fault Rupture Hazard Areas are faults identified on geological maps prepared and maintained by the Washington Department of Natural Resources (DNR), U.S. Geological Survey (USGS), Oregon Department of Geology and Mineral Industries (DOGAMI), Clark County, Washington, or identified from other available data or in the field by a qualified professional and adjacent areas within 100 feet.

3. Erosion Hazard Areas. Erosion Hazard Areas include Soil Erosion and Bank Erosion Hazard Areas.

a. Soil Erosion Hazard Areas. The following are designated Soil Erosion Hazard Areas:

Areas with soils identified as having a severe erosion hazard by the 1972 USDA Soil Conservation Service Soil Survey of Clark County Washington.

b. Bank Erosion Hazard Areas. Bank Erosion Hazard Areas are areas along lakes, streams, and rivers that are subject to regression or retreat due to lacustrine or fluvial processes and adjacent land within 100 feet.

B. Additional Critical Areas Report Requirements. In addition to the requirements of VMC 20.740.050, the following are Critical Areas Report requirements for development proposals in potential geologic hazard areas. These requirements may be adjusted as appropriate by the planning official. The Critical Areas Report will result in a conclusion as to whether the potential geologic hazard area is an actual geologic hazard area (See VMC 20.740.130(B)(6)). If it is, the Critical Areas Report requires additional information, mapping, and analysis (See VMC 20.740.130(B)(7)).

1. Identification of the site and project area (defined at VMC 20.150), topography in 2-foot contours (or other increment at the discretion of the planning official), gas, power, cable, fiber optic, telephone, sewer, water, and stormwater management facilities, wells, on-site septic systems, dikes, levees, and existing structures on the site plan required by VMC 20.740.050; and

2. Detailed review of field investigations, published data and references, data and conclusions from past geologic studies or investigations, site-specific measurements, tests, investigations, or studies, and the methods of data analysis and calculations that support the results, conclusions, and recommendations; and

3. Field investigation and evaluation of the areas on site for liquefaction or dynamic settlement, ground shaking amplification, fault rupture, and soil erosion hazards; and on or within 100 feet of the site for landslide and bank erosion hazards; and

4. A description of the surface and subsurface geology, hydrology, drainage patterns, soils, and vegetation on site for liquefaction or dynamic settlement, ground shaking amplification, fault rupture, and soil erosion hazards; and on or within 100 feet of the site for landslide and bank erosion hazards; and

5. Identification of the hazard area indicators that were found (if any) on site for liquefaction or dynamic settlement, ground shaking amplification, fault rupture, and soil erosion hazards; and on or within 100 feet of the site for landslide and bank erosion hazards; and

6. Conclusion as to whether there is a geologic hazard area on site or for landslide and bank erosion hazards on or within 100 feet of the site; and

7. If a liquefaction, dynamic settlement, ground shaking amplification, fault rupture, or soil erosion hazard is found to exist on site or if a landslide or bank erosion hazard is found to exist on or within 100 feet of the site:

a. Label and show on the site plan required by VMC 20.740.050:

1. The location(s), extent, and type(s) of geologic hazard area(s) identified; and

2. The location(s) and extent of any area(s) that must be left undisturbed to protect the proposed development from damage or destruction and to protect the hazard area(s) from the impacts of the proposed development; and

3. The boundaries of the area that may be disturbed.

4. The dimension of the closest distance(s) between the geologic hazard area(s) and the project area.

5. The dimension of the closest distance(s) [See VMC 20.170.030(C)] between any nondisturbance area [VMC 20.740.130(B)(7)(a)(2)] and the project area.

For bank erosion hazard areas, show these areas, boundaries, and dimensions based upon natural processes and, if applicable, proposed bank stabilization measures.

b. Analysis of the erosion processes on site for soil erosion hazard areas and on or within 100 feet of the site for bank erosion hazard areas.

c. Evaluation of the impact of the geologic hazard area(s) on the proposed development, other properties, and other critical areas.

1. Landslide hazard areas. The impact of the run-out hazard of landslide debris from both upslope and downslope shall be included in the evaluation.

2. Bank erosion hazard areas. Evaluation of impacts on other properties shall include properties both upstream and downstream of the subject property.

d. Evaluation of the impact of the proposed development on the geologic hazard area(s).

e. Assessments and conclusions regarding geologic hazard(s) for both existing and proposed (post-development) site conditions. The ultimate build-out scenarios must be considered and addressed in cases such as land division and master planning where build-out is not scheduled to occur as a direct or immediate result of project approval.

f. Written discussion of:

1. The risk of damage or destruction from the geologic hazard(s) with respect to human health and safety; infrastructure; the proposed development; other properties (both upstream and downstream for bank erosion hazard areas); and other critical areas; and

2. Whether and to what degree the proposed development would increase the risk from the geologic hazard(s), such as the occurrence of a landslide or the rate of regression.

g. Recommendations for mitigation of impacts to protect:

1. Human health and safety;

2. Infrastructure;

3. The proposed development;

4. Other properties (both upstream and downstream for bank erosion hazard areas);

5. Other critical areas; and

6. The hazard area during construction and for the anticipated life of the proposed development. The ultimate build-out scenarios must be considered and addressed in cases such as land division and master planning where build-out is not scheduled to occur as a direct or immediate result of project approval.

h. A demonstration of how the standards of VMC 20.740.130(C) applicable to each geologic hazard area will be met.

C. Performance Standards.

1. Landslide, Soil Erosion, and Bank Erosion Hazard Areas. Development in nondisturbance areas (VMC 20.740.130(B)(7)(a)(2)) shall be prohibited. In other areas, development in landslide, soil erosion, and bank erosion hazard areas and their buffers [VMC 20.740.130(C)(1)(j)] shall be prohibited except where the applicant has demonstrated compliance with or satisfaction of the following standards or requirements.

a. The applicant has demonstrated that during construction and for the anticipated life of the proposed development, the proposed use(s), activity(ies), and structure(s):

1. Will not increase the threat of the geological hazard beyond pre-development conditions; and

2. Will not adversely impact other critical areas wherever feasible given the type of critical areas involved and the characteristics of the site; and

3. Are designed so that the hazard to the proposed project is eliminated or mitigated to a level equal to or less than pre-development conditions; and

4. The life safety risk is minimal or eliminated; and

5. Are certified by a qualified professional as safe as designed and under anticipated conditions.

Landslide hazard areas may be eliminated through grading based on a Critical Areas Report which demonstrates that the slope will be stabilized prepared by a qualified professional (in this case a licensed Engineering Geologist or Professional Engineer). The Critical Areas Permit shall be conditioned on a final inspection approval confirming that the grading and site are stable. At the applicant’s expense, after site grading, (a) the qualified professional who prepared the Critical Areas Report shall provide inspection specifications; and (b) an inspector acceptable to the City Building Official shall inspect the grading and the site and submit a report to the City indicating whether the site is stable.

b. A plan for revegetation and landscape maintenance to ensure soil stabilization shall be developed and implemented in accordance with the mitigation plan requirements of VMC 20.740.050(F).

c. Clearing, grading, uprooting, or otherwise impairing the soil stabilizing function of vegetation shall be prohibited during the wet season (November 1st to May 1st), except as authorized under a valid state or federal permit or a City Type I permit [VMC 20.740.040(A)(2)(f)].

d. Drainage patterns shall not be altered such that potential for damage or risk to the proposed project, the geologic hazard area, or other critical areas or buffers is increased.

e. The requirements of VMC 14.24, Erosion Control shall be met.

f. Trails shall be for pedestrian and nonmotorized vehicular use only and shall be the minimum width necessary to meet applicable regulations.

g. Roads in Landslide and Bank Erosion Hazard Areas. A road through or across a landslide or bank erosion hazard area shall meet the standards of VMC 20.740.130(C)(1)(a)-(f) and shall not be:

1. The sole access for a proposed subdivision (not including short subdivision) or critical facility;

2. Longer than 200 feet;

3. Steeper than a 15% grade.

h. Markers and Signs in Landslide Hazard Areas.

1. The boundary at the outer edge of landslide area tracts and easements shall be delineated with permanent survey stakes, using iron or concrete markers as established by local survey standards.

2. The boundary at the outer edge of the furthest of the landslide hazard area, nondisturbance area [VMC 20.740.130(B)(7)(a)(2)], or buffer shall be identified with temporary signs prior to any site alteration. Such temporary signs shall be replaced with permanent signs prior to occupancy or use of the site.

3. These provisions may be modified by the planning official as necessary to ensure protection of sensitive features or wildlife needs.

i. Bank Stabilization for Existing Development in Bank Erosion Hazard Areas.

1. Bank stabilization measures may be employed to protect an existing structure when a Critical Areas Report conclusively demonstrates all of the following:

a. Bank erosion threatens an established use or existing structure(s); and

b. The threatened structure(s) cannot be relocated landward of any nondisturbance area [VMC 20.740.130(B)(7)(a)(2)]; and

c. Where applicable, bank stabilization measures are necessary to the operation and location of water-dependent, water-related, or water enjoyment activities consistent with the City of Vancouver Shoreline Management Master Program; and

d. Bank stabilization measures will not cause a significant adverse impact on upstream or downstream properties or an impact that cannot be mitigated without developing bank stabilization measures for those properties; and

e. Bank stabilization measures will not cause a significant adverse impact on fish, wildlife, or their habitats protected by this chapter.

2. When bank stabilization is allowed, it shall be accomplished using beach nourishment, bioengineering (soft armoring) techniques, or a combination of the two. Other techniques may be used when an approved Critical Areas Report demonstrates conclusively that beach nourishment, bioengineering (soft armoring) techniques, or a combination of the two will not provide sufficient protection for the remaining useful life of the structure(s) to be protected.

3. When bank stabilization is allowed, the pertinent policies and regulations of the City of Vancouver Shoreline Management Master Program shall apply in addition to the requirements of this section. The terms and conditions of any other required state or federal permit or approval shall also apply.

j. Buffer. The following regulations apply to landslide and bank erosion hazard area buffers. No buffer is required for soil erosion hazard areas. Buffers may be included in nondisturbance areas [VMC 20.740.130(B)(7)(a)(2)] and required planting and maintenance activities may be undertaken within them.

1. Buffer width shall be measured on a horizontal plane from a perpendicular line established at all edges of the geologic hazard area [See VMC 20.170.030(B) and (K)].

2. A vegetated buffer shall be maintained around all landslide and bank erosion hazard areas. No alteration to the buffer shall be undertaken without an erosion control plan approved pursuant to the provisions of VMC 14.24, Erosion Control and this chapter. New plantings shall consist of native vegetation. Maintenance shall be the responsibility of the property owner.

3. The minimum buffer width for bank erosion hazard areas shall be the distance recommended in an approved Critical Areas Report.

4. The minimum buffer width for landslide hazard areas shall be the greatest of the following distances:

a. 50 feet from all edges of the landslide hazard area; or

b. A distance of 1/3 the height of the slope at the top of the slope and a distance of 1/2 the height of the slope at the bottom of the slope [See VMC 20.170.030(J)]; or

c. The minimum distance(s) recommended in an approved Critical Areas Report.

5. A larger buffer width may be required for landslide and bank erosion hazard areas at the discretion of the planning official when:

a. The adjacent land is susceptible to severe erosion and erosion control measures will not effectively prevent adverse impacts; or

b. The area has a severe risk of slope failure or downslope stormwater drainage impacts; or

c. The area is directly adjacent to a riparian management area or wetland; or

d. Recommended in an approved Critical Areas Report.

6. The buffer width for landslide hazard areas may be reduced to as little as the smallest of the distances identified in VMC 20.740.130(C)(1)(j)(4) at the discretion of the planning official when the dimensions of the landslide hazard area are smaller than those distances.

2. Seismic Hazard Areas

a. Liquefaction or Dynamic Settlement Hazard Areas. All building structures in liquefaction or dynamic settlement hazard areas shall comply with the requirements of VMC Title 17, Building and Construction. No buffer is required for liquefaction or dynamic settlement hazard areas.

b. Ground Shaking Amplification Hazard Areas. All building structures in ground shaking amplification hazard areas shall comply with the requirements of VMC Title 17, Building and Construction applicable to the NEHRP soil classification of the subject property. No buffer is required for ground shaking amplification hazard areas.

c. Fault Rupture Hazard Areas.

1. A road through or across a fault rupture hazard area shall not be:

a. The sole access for a proposed subdivision (not including short subdivision) or critical facility;

b. Longer than 200 feet’;

c. Steeper than a 15% grade.

2. Structures for human habitation and critical facilities shall be prohibited within fault rupture hazard areas and buffers.

3. Buffer.

a. Buffer width shall be measured on a horizontal plane from a perpendicular line established at all edges of the geologic hazard area [See VMC 20.170.030(B)].

b. The buffer width shall be the greater of the following distances:

i. 50 feet from all edges of a fault rupture hazard area, except where critical facilities are involved, the minimum buffer distance shall be 100 feet [See VMC 20.170.030(L)]; or

ii. The minimum distance recommended in an approved Critical Areas Report.

c. A larger buffer width may be required when the planning official determines that the buffer is not adequate to protect the proposed development. (Ord. M-3844 § 2, 10/01/2007; Ord. M-3692, Added, 02/28/2005, Sec 2)