14.37.180 Standards for geologically sensitive areas--Specific

14.37.180 Standards for geologically sensitive areas--Specific.

A. Undevelopable Geologically Sensitive Areas. Ravine sidewalls, bluffs and their buffers and hillsides with a slope greater than forty percent shall remain undeveloped except as otherwise provided in this chapter. The top, toe, and edges of ravine sidewalls, bluffs and the outside edge of their buffers and hillsides with forty percent slope or greater shall be determined and field marked by a qualified geotechnical engineer.

B. Landslide Hazard Areas. Hillsides containing or adjacent to landslide hazard areas shall be altered only when the site plan review committee concludes, based on required reports, the following:

1. There will be no increase in surface water discharge or sedimentation to adjacent properties; and

2. There will be no decrease in slope stability on adjacent properties; and

3. The alteration conforms to all other requirements of subsection E of this section; and

4. Either:

a. There is no hazard as proven by evidence of no landslide activity in the past in the vicinity of the proposed development and a quantitative analysis of slope stability indicates no significant risk to the development proposal and adjacent properties; or

b. The landslide hazard area can be modified or the development proposal can be designed so that the landslide hazard is eliminated or mitigated so that the site is as safe as a site without a landslide hazard; or

c. The alteration is so minor as not to pose a threat.

1. Buffers. A fifty-foot undisturbed buffer of native vegetation shall be established from the top, toe, and sides of all ravine sidewalls and bluffs.

2. Buffer Reduction. The buffer may be reduced when expert verification and environmental information demonstrate to the satisfaction of the site plan review committee or hearings examiner, whichever is applicable, that the proposed construction method will:

a. Not adversely impact the stability of ravine sidewalls and bluffs; and

b. Not increase erosion and mass movement potential of ravine sidewalls and bluffs; and

c. Use construction techniques which minimize disruption of the existing topography and vegetation; and

d. Include measures to overcome any geological, soils, and hydrological constraints of the site. The buffer may be reduced by no more than fifty percent.

3. Additional Buffers. The site plan review committee may require increased buffers if environmental studies indicate such increases are necessary to mitigate landslide, seismic and erosion hazards, or as otherwise necessary to protect the public health, safety and welfare.

4. Building Setback Lines. A building setback line of ten feet is required from the edge of any buffer of a ravine sidewall or bluff. Minor structural intrusions into the area of the building setback line may be allowed if it is determined that such intrusions will not negatively impact the geologically sensitive area.

5. All buffers shall be measured from the top, toe, and sides of all ravine sidewalls or bluffs.

D. Developable Geologically Sensitive Areas. Hillsides other than ravine sidewalls and bluffs and their buffers and hillsides less than forty percent slope are developable pursuant to the provisions of this chapter. The applicant shall clearly and convincingly demonstrate to the satisfaction of the site plan review committee or hearings examiner, whichever is applicable, that the proposal incorporates measures protecting the public health, safety, and welfare.

E. Hillsides of Fifteen Percent Slope and Greater--Disturbance Limitations. Development on hillsides shall comply with the following requirements regarding disturbance limitations, development location, development design, construction techniques and landscaping:

1. Amount of Disturbance Allowed. The following chart sets forth the maximum slope disturbance allowed on a development site:

Slope	Amount of Slope Which Can be Disturbed	Factor
0-15%	100%	1.00
15-25%	60%	.60
25-40%	45%	.45
40%+	0%	.00

The overall amount of disturbance allowed on development sites which have any combination of the above slope categories shall be determined by the following formula:

(Square footage of site having 0-15% slopes) x 1.00 + (Square footage of site having 15-25% slopes) x .60 + (Square footage of site having 25-40% slopes) x .45 = Total Amount of Allowable Site Disturbance.

The intent of this section shall be to provide reasonable flexibility in site development while promoting the intent of working with existing topography as opposed to against it.

a. Structures and improvements shall be clustered to retain as much open space as possible and the natural topographic character of the slope; and

b. Structures and improvements shall conform to the natural contour of the slope, foundations must be tiered to generally conform to the existing topography of the site; and

c. Structures and improvements shall be located to preserve the most sensitive portion of the site and its natural land forms and vegetation.

a. The footprint of buildings and other disturbed areas shall be minimized. The least number of buildings is desirable in order to consolidate the development; and

b. Use of common access drives and utility corridors is required where feasible; and

c. Impervious lot coverage shall be minimized. With the exception of detached single family structures, under-structure parking and multi-level structures shall be incorporated where feasible; and

d. Roads, walkways and parking areas shall be designed to parallel the natural contours of the hillsides while maintaining consolidated areas of natural topography and vegetation. Access shall be located in the least sensitive area feasible; and

e. Use of retaining walls which allow the maintenance of existing natural slope areas is preferred over graded artificial slopes.

a. Use of foundation walls as retaining walls is preferable to rock or concrete walls built separately and away from the building. Freestanding retaining devices are only permitted when they cannot be designed as structural elements of the building foundation; and

b. Structures shall be tiered to conform to existing topography and to minimize topographic modification.

a. All requirements of the grading chapter of the city’s adopted building code shall be satisfied. Requirements under this chapter shall be consolidated with review requirements of the grading chapter of the building code to provide a coordinated review process.

6. Landscaping. The disturbed area of a development site not used for buildings and other improvements shall be landscaped according to a landscape design which will achieve a minimum forty percent coverage by the canopy of trees and shrubs within ten years to provide habitat desirable to native western Washington birds. The trees and shrubs shall be a mix of shade, flowering, and coniferous and broad-leaf evergreens that are either native to the Puget Sound region or are valuable to western Washington birds. The Department of Wildlife “Plants for Wildlife in Western Washington” shall be used as a general guide.

a. Trees shall be the following size at time of planting and shall conform to the “American Standard for Nursery Stock”:

(1) Single-stem shade and flowering trees shall be a minimum one-and-one-half-inch to two-inch caliper trunk as measured six inches above the ground.

(2) Multi-stem shade and flowering trees shall be a minimum height of eight feet as measured from the ground level to the average uppermost point of growth of the plant.

(3) Coniferous evergreen trees shall be a minimum height of six feet as measured from the ground to the midpoint between the uppermost whorl and the tip of the leader. For species of trees without whorls, minimum height shall be measured to the uppermost side growth. The ratio of height to spread shall not be less than five to three.

(4) Broad-leaf evergreen trees shall be a minimum height of four feet as measured from the ground level to where the main part of the plant ends, not to the tip of a thin shoot.

b. Shrubs shall be the following size at time of planting and shall conform to the “American Standard for Nursery Stock”:

(1) Dwarf and semi-dwarf deciduous shrubs shall be a minimum height of two to two and one-half feet above grade, and either a number three container size for container grown plants, ten-inch diameter root ball for balled and burlapped plants, or eleven-inch root spread for bare root plants.

(2) Strong-growing deciduous shrubs shall be a minimum height of two to three feet above grade, and either a number three container size for container grown plants, ten-inch diameter root ball for balled and burlapped plants, or eleven-inch root spread for bare root plants.

(3) Coniferous and broad-leaf evergreen shrubs (Types 1, 2, and 3) shall be a minimum height of two to two and one-half feet spread or height, and either a minimum number three container size for container grown plants or twelve-inch diameter root ball for balled and burlapped plants.

7. Erosion Control. A special drainage and erosion control plan shall be prepared outlining measures being taken to effectively control drainage and erosion. Landscaping activities and grading and excavation activities may be limited to specific times of the year based upon an analysis of soil types, proximity of wetlands, or other factors that may indicate an unacceptable risk of erosion hazards and related impacts (refer to the current City of Lacey Stormwater Design Manual).

F. Seismic Hazard Areas. The city of Lacey acknowledges it is in a seismic hazard zone and shall pursue more specific identification of those areas in the city at the greatest risk. Once said areas are identified, specific criteria designed to protect the public safety shall be developed. (Ord. 1505 §55, 2017; Ord. 1496 §27, 2016; Ord. 1208 §59, 2003; Ord. 935 §11 (part), 1992).