Village of Kenilworth: Site Development Regulations

Transcription

1 Village of Kenilworth: Site Development Regulations WHITE PAPER ON STEEP SLOPES Prepared by Teska Associates, Inc. JANUARY 12, 2016

2

3 GENERAL OUTLINE Introduction The Slope of Land Defining Steep Slopes How do Steep Slopes Fail? What are the Impacts of Steep Slope Failure? Protection of Steep Slopes Through Regulation Common Steep Slopes Protection Measures Steep Slope Regulations in Neighboring Illinois Communities Steep Slopes in Kenilworth Conclusion

4 INTRODUCTION This white paper provides background on the intent and reasoning applied in development of the recently adopted Village of Kenilworth ordinance to regulate steep slope areas. The paper defines steep slopes, what causes their potential failure, how they can be protected and the purpose behind development regulations. It also includes a survey of steep slope development regulation practices along the North Shore, and current practices in Kenilworth. Steep slopes by their very nature, may contain volatile sediment, rock and soils, which are subject to unstable conditions including erosion and surface and subsurface movement of water. In addition, slope stability is affected by the quality and root structure of natural ground cover and/or weight on the top of the edge of such steep slopes. Home development around steep slopes also requires infrastructure, including but not limited to water and sewer lines, roads, and utility lines. Installing and maintaining such development and infrastructure requires excavation, footings, paving, and excessive earthmoving. Such development activity, in addition to uncontrolled stormwater and impervious surface areas, can lead to greater slope instability. In order to protect these natural resources, environmental features and systems, and scenic vistas, local governments regulate construction and development on and around steep slopes. Regulating the intensity of development according to the natural characteristics of steep slope terrain, such as degree of sloping, significant vegetation, and soil stability and existing drainage patterns allow for development of steep slope lots, while minimizing the physical impact of such development. Steep slope regulations thus protect public health, safety, and welfare by preventing the factors that lead to failure. They also protect private property by allowing property owners to maintain and reasonably improve existing homes near the ravines and bluff areas along the lakefront. 1

5 THE SLOPE OF LAND Slope of the land is a fundamental characteristic that defines a steep slope. It is the rate of change in elevation between two points in a given area. It is measured by determining the difference in elevation between those two points (the rise) and dividing the elevation by the horizontal distance between them (the run); it is expressed as a ratio or percentage (American Planning Association, 2006). For example, a stretch of land 100 feet long that rises 10 feet in elevation has a slope ratio of 10/100 or a 10 percent. The slope of land is typically classified into the following ranges (Source- Soil Conservation Service): 0% to 3% Generally suitable for all development and uses. 3% to 8% Suitable for medium-density residential development, agriculture, industrial, and institutional uses. 8% to 15% Suitable for moderate to low-density residential development, but great care should be exercised in the location of any commercial, industrial or institutional uses. 15% to 25% Only suitable for low-density residential, limited agricultural and recreational uses. Over 25% Only used for open spa ce and certain recreational uses. Defining what constitutes steep for the purposes of slope regulation is at the discretion of municipalities, provided that the definition is reasonable. Some communities regulate slopes starting at 15 percent. Kenilworth and nearby communities like Glencoe, Highland Park, Lake Bluff and Lake Forest consider slopes greater than 10 percent as steep slopes. 2

6 DEFINING STEEP SLOPES A steep slope is generally defined as land where the slope ascent or descent is greater than ten percent. Although steep slopes typically include hills, mountains, and gullies within its broad definition, steep slopes in Northeastern Illinois commonly consist of ravines and bluffs, specifically those along Lake Michigan. A ravine is an erosional feature cut into the side of a hill, V-shaped when young, U-shaped with age; while a bluff is a near-vertical exposure of unconsolidated sediment (as opposed to a cliff, which is a near-vertical exposure of rock). Terminology related to steep slopes as noted in the Kenilworth ordinance is explained in the figures and definitions that follow: Figure 1: Illustration of defined terms for Ravine 3

7 Figure 2: Illustration of defined terms for Bluff Bluff An elevated segment of the Lake Michigan shoreline above the beach which normally has a precipitous front inclining steeply on the lakeward side. Ravine A deep gully or gorge worn by the flow of water to Lake Michigan. In this chapter, all references to ravine shall refer that portion of the Skokie Ditch located east of Sheridan Road and north of Kenilworth Avenue. Tableland Land at the top of a bluff or ravine where the cross slope in any direction does not exceed ten (10) percent. Toe of bluff The edge of the ravine or bluff where the slope is less than ten percent or where the slope reverses direction. In Kenilworth, for properties that have retaining wall at the edge of the bluff, the toe is typically the outer edge of the lowermost retaining wall. Steep Slope Land comprising or adjacent to a lake bluff or ravine where the slope in ascent or descent exceeds ten (10) percent from the horizontal. Steep Slope Line A line representing the intersection of the tableland and the steep slope. It is commonly indicated on plats of survey or other documents as the top of bluff. Steep Slope Zone In the case of a ravine, that portion of a lot that includes the Steep Slope of the ravine and lies between the bottom of the ravine and a line drawn ten feet behind the Steep Slope Line at the top edge of the ravine and away from the bottom of the ravine. For the purposes of this chapter, the ravine means the Skokie Ditch east of Sheridan Road. The Steep Slope Zone shall include all retaining walls located between the bottom of the ravine and the Steep Slope line. In the case of a bluff, that portion of a lot that includes the Steep Slope and lies between the water s edge of Lake Michigan and a line drawn thirty-five (35) feet behind the Steep Slope Line at the top edge of the bluff and away from the bottom of the bluff. The Steep Slope Zone shall include all retaining walls located between Lake Michigan and the Steep Slope line. 4

8 HOW DO STEEP SLOPES FAIL? Slopes are naturally unstable as they can be affected by natural or man-made factors that can cause it to fail. Slope failure can be in the form of site disruption, erosion, slippage or sliding. The characteristics that influence slope stability include vegetation, slope drainage, slope topography (shape and steepness), soil type and moisture, upslope activities, and changes to the slope (adding or removing soil from the slope). Some of the causes of slope failures are included below. MAN-MADE CAUSES Addition of excessive weight and pressure on the top of the bluff Slopes cut at too steep an angle or soil excavation without proper shoring to prevent collapse Improper construction, earth moving, and development along a steep slope Redirected storm water runoff concentrated in areas not prepared to receive them Disruption or removal of deep rooted native vegetation that help stabilize the slope Uncontrolled stormwater runoff Additional surface run-off due to an increase in impervious areas Excessive irrigation of hillside plantings and lawns Run-off of ground water pumped out by sump pumps NATURAL FACTORS Weak or weathered materials; Wave erosion of slope toe; Subterranean erosion; Tectonic instability; Intensive rainfall or snow melt; and Freeze /thaw cycle 5

9 WHAT ARE THE IMPACTS OF STEEP SLOPE FAILURE? When steep slopes fail, they can cause significant property damage, as well as pose a threat to public life and safety. Significant landslides can include huge, slow-moving slides that severely damaged entire neighborhoods, smaller, quick-moving, avalanche like debris flows, and large, rapid slope failure that obliterate homes in their paths. Slope failures can disrupt roads and infrastructure, change the natural face of the bluff or ravine, and are often very costly - a problem to both public agencies and private property owners. Communities have recognized that for both safety, as well as fiscal reasons, local governments need to be more active in preventing failures by protecting steep slopes. PROTECTION OF STEEP SLOPES THROUGH REGULATIONS Purpose of steep slope regulations The purpose of steep slope regulations is not to prevent development within and along steep slopes, but to ensure that such development does not jeopardize slope stability to either the developed property or adjacent properties. These regulations, similar to other regulations (i.e. building code, fire code), are intended to further the public interest by protecting people and property from the potentially hazardous geological and hydrological conditions characteristic of ravine and bluff areas. Steep slope regulations also help manage development, construction, and earth moving in, along, or near steep slope areas in order to protect slope stability. Steep slope protection measures can not totally eliminate some amount of natural slope erosion; however, stable slopes and the maintenance of stable ecological relationships can minimize environmental degradation of the steep sloped land. Background and origin Through local police powers, as granted through Zoning Enabling Legislation, local governments are able to regulate the intensity and means of development within their jurisdiction in order to protect the community s health, safety, and welfare. The primary legislative means of regulating development is through land use zoning regulations, subdivision regulations, and building codes. The earliest steep slope regulations took the form of grading ordinances, established though building codes for the City and County of Los Angeles in the early 1950 s. These early grading ordinances were focused on protecting life and property from un-engineered or improved hillsides, which were in response to landslides during heavy rains between 1952 and Subsequent to the early southern California grading ordinances, the Uniform Building Code in 1964 adopted similar grading requirements, which were then adopted by municipalities across the country. These early grading ordinances have been highly successful in improving the safety of steep slope development. However, over time with increased development pressure, more detailed and sophisticated steep slope regulations have evolved. 26

10 Goals of the regulations Steep slope regulations often focus on restricting the location, nature, and intensity of development, while allowing for reasonable use of the property and protecting G the public health, safety, and welfare. The major goals of steep slope regulations are included below: 1 Utilizing appropriate engineering technology to protect the slope during and subsequent to construction and development; 2 Utilizing building techniques that increase slope stability; 3 Reducing storm water runoff and soil erosion by encouraging the preservation of trees and other vegetation and, where necessary, requiring revegetation; 4 Permitting intensity of development compatible with the natural characteristics of steep slope terrain, such as degree of sloping, soil suitability and existing natural and man-made drainage patterns; 5 Seeking a balance between development and natural preservation; and 6 Preserving the scenic quality of the ravine and bluff environment through the retention of dominant steep slopes and ridges in a vegetated state instead of being dominated by man-made retaining walls that change the natural character of the lakefront. Above left and right: Examples of steep slope in Kenilworth

11 COMMON STEEP SLOPE PROTECTION MEASURES The following are different types of protection measures to increase slope stability: Development standards/ construction techniques As noted, slope failures can be caused by man-made factors or activities. Hence it is important to prevent slope instability that can be caused by development that adds weight to top of marginally stable slopes, unnecessary earth moving, and removal of natural vegetation that can increase soil loss due to erosion. Limiting and providing guidelines for earth-moving in and around steep slope areas, especially during construction activities will help protect slope stability. Maintaining a setback from the top of bluff so that the major building footprint is sufficiently set back from the steep slope is also important from a stability point of view. Vegetation Maintaining and strengthening of natural ravine stormwater channels with deep rooted native vegetation helps stabilize the slope. Ensuring that the plant mix is of perennial and woody species is important to ensure coverage throughout the year. Reason to regulate To protect and enhance slope stability and prevent/reduce erosion. Potential concerns with regulation May limit the portion of the site that can be developed and directs character of the landscape. Reason to regulate To protect slope stability and existing trees/vegetation. Potential concerns with regulation Increase in costs related to construction and space constraints for construction equipment to maneuver on (especially on small sites). Left and above: Examples of steep slope in Kenilworth Figure 7 Building Elevations

12 COMMON STEEP SLOPE PROTECTION MEASURES Control of stormwater runoff Steep slope failures are often caused by erosion, and such erosion can often be the result of unmanaged and uncontrolled stormwater runoff. Measures to reduce uncontrolled stormwater runoff include: Maintain any natural drainage ways along the bluff. Require all roof stormwater runoff to be piped away from the bluff or ravine. Control the discharge location of ground water by sump pumps so that it does not cause erosion or impact the bluff or ravine. Require the lateral boring of all sub-surface utilities. Require interceptor ditches. Maintain predevelopment lot flow rates. Require stormwater discharge into energy dispersion devices to slow down fast moving stormwater and prevent soil erosion. Prevent the alteration of runoff onto adjacent properties. Reason to regulate To reduce erosion from stormwater run-off and protect slope stability. Potential concerns with regulation Cost of improvements to manage stormwater runoff. Impervious area In order to protect steep slopes, many communities have adopted measures to limit the total amount of building square footage or FAR that can be placed on steep slope lots to reduce the amount of impervious surface area and in turn reduce the stormwater runoff. Reason to regulate To reduce stormwater run-off and protect slope stability. Potential concerns with regulation May limit the amount of area for use of property near the water. Engineering When passive measures to protect slope stability, such as minimizing site disturbance and managing stormwater runoff are not viable options, alternate site improvements can be considered to protect slope stability. Engineered structures (retaining walls, deep footings) that reduce the impact of soil pressure on the steep slope can be used. Such engineering improvements can strengthen and/or limit the impact of development on steep slopes, as well as manage stormwater runoff. Reason to regulate To ensure consistency with the character of the landscaped topography and protect slope stability. Potential concerns with regulation May impact the aesthetics of the slope area. 10 7

13 STEEP SLOPE REGULATIONS IN NEIGHBORING ILLINOIS COMMUNITIES Steep slope protection measures are found throughout a survey of steep slope regulations in communities. However, due to different political, geotechnical, and environmental conditions, steep slope regulations focus on different issues in each community like a focus on scenic and vista preservation, in addition to steep slope preservation. These regulations typically include: establishing a higher minimum lot size for steep slopes; reducing the number of dwelling units on steep slope lands; bluff and ravine protection to safeguard life and property; as well as preservation for aesthetic purposes. Above: Example of steep slope in Kenilworth Regardless of the focus of the regulations, most municipalities have a list of performance standards that Staff, Village/City Boards, Plan Commissions, or ZBAs use to review development on steep slopes. In addition, most municipalities require that development within the steep slope be reviewed by the Village/City Board, Plan Commission, or ZBA rather than just administratively. The table in Attachment 1 compares the steep slope regulations of communities neighboring Kenilworth. 28

14 STEEP SLOPES IN KENILWORTH The topography of the eastern edge of the Village of Kenilworth is characterized by a bluff along the lakefront and a ravine (Skokie Ditch) just north of Kenilworth Avenue, which is part of the distinctive ravine-bluff formation along the Lake Michigan shoreline north of the Chicago. This bluff has an average slope of 40%, with some areas being as steep as a nearly 80%. These steep slopes are a valuable ecological and scenic resource. However, they require special care if they are to be preserved. The Village of Kenilworth steep slope ordinance helps to maintain this unique natural resource and protect against potential steep slope failures. The ordinance also sets standards for types of construction allowed near and on steep slopes, and provides standards regarding forms and methods of construction. Properties that have engineered retaining walls appear in general to be more stable than the ones with only vegetation along the toe of the bluff. While more natural looking without retaining walls, the wave and wind action at the toe of the bluff makes this area vulnerable to being washed away and collapsing. Similarly, some property owners protect this area with rocks as a way to decrease the erosion. Character of the bluff and ravine in Kenilworth The Kenilworth bluff along Lake Michigan is part of residential properties and is well vegetated except for a strip of beach area along the eastern edge. Common features along the bluff include flights of steps, pathways, fences, low height retaining walls, decks, screen houses, boat houses and retaining walls sometimes with large rocks at the toe of the bluff. Properties that do not have masonry or concrete retaining walls along the toe of the bluff have vegetation instead, and face erosion. The vegetation along the bluff includes grasses, shrubs, and a number of mature trees. The ravine (Skokie Ditch) is also well vegetated naturally. Above: Examples of engineered retaining walls 11

15 Analysis of the current zoning regulations with respect to steep slopes All properties along steep slopes in the Village of Kenilworth are located in the R1- Single Family Residential zoning district, except for the Village owned beach, which is zoned M2- Municipal Land. Consistent with other zoning districts, the R1 zoning district limits bulk development through setbacks (front, rear, side), height, maximum lot coverage, maximum building coverage, minimum building floor area, and the amount of impervious surface area. Prior to adoption of the new ordinance, principal buildings could be located as close as 25 from the rear lot line, there were no restrictions on the location of accessory buildings within the rear and side yards, and swimming pools could be located within 8 of the rear lot line, all of which had the potential of placing these structures too close to or within the bluff or the ravine itself. In addition, there were no restrictions on the impervious surface area along the steep slopes or stormwater runoff recommendations, which can impact the level of erosion on the steep slopes. Analysis of the current zoning regulations with respect to steep slopes Calculation of lot area on lakefront properties also is a concern in that it includes the entire site in determining maximum building size. While a formula is applied to determine how lots size translates into home size, it is generally the case that a larger lot translates into a larger home. The logic is that the ratio of lot to home size creates a consistent and attractive character for the community. However, given that a substantial portion of a lakefront property may be comprised of beach and slope, including those areas in the lot size calculation to determine building size can facilitate a home that is oversized and out of character with the area. Some communities address this issue excluding some of the property (for example the beach and slope) from the lot area basis to determine building size. Other Kenilworth zoning items related to steep slope are the location of rear lot lines on lakefront property and the manner in which those lot areas are calculated, which were not addressed by the recently adopted ordinance. Currently, rear lot lines are defined as the water s edge of Lake Michigan. This creates difficulties in that the edge of the water moves regularly based on time of day or month, and on a longer term basis is subject to the overall lake depth. This fact creates uncertainty as to the location of the rear lot line and related setbacks. In addition, this variable lot line impacts lot area calculations. 12

16 Summary of Kenilworth Ordinance Regulating Steep Slope Areas Adoption of the ordinance to regulate steep slope areas addresses issues related to supporting slope stability and protecting of property. Primary steep slope standards of the new ordinance include: than five feet, and with limitation the size of landings and platforms. Decks are permitted if no larger than 100 square feet, unless engineering analysis is proved showing no jeopardy to slope stability. Construction of structures in steep slope zones that are bluffs or ravines is limited to retaining walls and other structures necessary for slope stabilization. However, those structures may not increase tableland or create table areas in the steep slope zone. One accessory structure may be built in a steep slope zone for bluffs, but no larger than 150 square feet or taller than 11 feet. Also, the structure may not impact slope stability of the property or adjacent properties, nor be visible from adjacent tableland. Rebuilt or remodeled structures in steep slope zones that are bluffs or ravines may be built on the exact foundation of a previously existing structure. However, they may not extend beyond the previous foundation or extend above the previous height of structures. Plans for construction must be prepared by an architect or structural engineer certifying that the existing founding will support the new construction. The ordinance provides detailed requirements on means and methods of construction in steep slope areas, including standards for vegetation and hydrological controls. In steep slope zones for bluffs, mechanical or electrical lifts, bridges, decks, walkways, steps, and/or fences may be constructed if they do not unnecessarily obstruct the flow of light and air, or interfere with utility lines. Stairs may also be constructed, but no wider Left and above: Examples of steep slope in Kenilworth 11

17 CONCLUSION As Kenilworth is a built out community with already developed steep slope areas, regulation of steep slopes is limited to ensuring stability of the bluff and preservation of the character of the lakefront. As construction activity and drainage patterns contribute to erosion, providing guidelines in the form of the recently adopted regulations for these activities will help preserve the stability of the steep slope. 13

18 COMPARISON OF DRAINAGE AND GRADING REGULATIONS GLENCOE HIGHLAND PARK LAKE FOREST WINNETKA LAKE BLUFF INTERNATIONAL BUILDING CODE (2012) Primary purpose Protect- bluff and ravine to avoid degradation Protect-individual property rights Public interest served by protection of people and property from potentially hazardous geological and hydrological conditions. The ravine and coastal steep slopes are an inherent natural resource which imparts a unique and substantial character. Erosion, slope failures, and loss of vegetation along one portion of a slope can have an adverse impact upon adjacent sloped areas. Because these areas may be abused so as to create conditions which jeopardize property values and the natural ecosystem, appropriate controls are necessary. (aesthetics and safety) Protect public and private property from damage or destruction resulting from the natural erosion processes occurring within the ravines and bluffs along the shore of Lake Michigan, or abnormal or accelerated ravine and bluff erosion resulting from land development and construction activities occurring on adjacent or nearby properties, and to protect the fragile ravine and bluff ecosystem from unwarranted damage or destruction caused by land development and construction activities. No steep slope ordinance. Only slope related note - When slopes are used to provide a transition between the existing grade and the proposed grade for the top of the permanent fill, or for the construction of a compensatory storage basin, those slopes will be limited to a maximum of 1:6, or 1 foot of vertical rise for every 6 feet of horizontal run. The Village of Lake Bluff s ravine and bluff areas, which are inherently fragile and subject to erosion due to glacially formed soils containing unstable sediment, rock, and silt, provide a unique natural resource to the Village and to its residents that must be preserved and protected. For slope protection (with respect to man-made slopes) to prevent soil erosion. Definition of steep Slope impact area- Line representing the intersection of table land and a 22 degree slope (2.5H:1V) extending upward from the toe of the bluff or ravine. Also includes area of the lot where the slope of the lot is steeper than 5.7 degrees (10H:1V). Not specifically defined, notes as area that has ravines and bluffs / exhibit steep slopes containing unstable sediment, rock and soils. RAVINE AREA- The Ravine Area shall include all property within or adjacent to a ravine beginning at the point of intersection of a line with the table land, said line extending from the toe of the slope upward at a vertical angle of twenty -two (22) degrees. Not defined. Not defined. Steep slope line- A line representing the intersection of the table land with a 27 degree slope (2H:1V) extending upward from the toe of the bluff or ravine. Steep Slope Zone- Area between steep slope line and the toe line. RAVINE EDGE - That point on the ravine side of the table land where the slope of the land first exceeds ten (10) percent. TABLE LAND - Land where the slope in any direction does not exceed ten (10) percent. Table Land- Land at top of bluff/ravine where slope is less than a 5.7 degree slope (10H:1V) Toe line- Land at bottom of bluff/ravine where slope is less than a 5.7 degree slope (10H:1V) TOE OF SLOPE - The toe of the ravine or bluff slope is that point in the ravine or bluff where the slope is less than twenty-two (22) degrees or where the slope reverses directions. On compound slopes where there may be more than one possible toe location, the controlling point shall be whichever toe location provides the greater ravine or bluff area.

19 COMPARISON OF DRAINAGE AND GRADING REGULATIONS (continued) GLENCOE HIGHLAND PARK LAKE FOREST WINNETKA LAKE BLUFF INTERNATIONAL BUILDING CODE (2012) Setbacks and setback from bluff As defined by slope impact area. No building construction 10 from top of ravine. 40 from top of bluff. Swimming pools prohibited within 10 of Steep Slope Zone. Accessory structures no greater than 150 sq/ft may be built within the Steep Slope Setback. Lifts, bridges, walkways, steps and fences may be built within steep slope No building construction allowed within 20 from top of ravine. 75 from top of bluff. The City Engineer may approve encroachments into the bluff or ravine setback area for the construction of landscape features, auxiliary buildings (slab foundation), bridges, wood decks or other similar facilities No principal structure may be constructed 10 from Top Ravine Edge. 40 from Top Bluff Edge. However, paths, steps, and benches are allowed to be located within a bluff or ravine. No swimming pool may be built within 20 from top edge of ravine and 40 from top edge of bluff. Decks may cantilever over bluff or ravine, provided that no pier foundations or supports are located within the bluff or ravine. H/2 but 2 min. and 20 max. from toe of slope. H/2 but 2 min. and 10 max. from top of slope. (J108.1) Accessory structures may be built within 10 from the Top Bluff Edge. The Village Engineer may approve certain other activities (erosion control and slope stabilization, public utility and other improvement projects, drainage improvements). FAR calculation All gross floor area calculations are based on lot size. *There are exclusions for certain square footage of garages, porches, unfinished and finished attics, undereaves, courtyards and basements. All FAR based on the lot area. Some overlay zones also apply to calculation. All max. square footage is based on lot size with exclusions for certain square footage of garages, porches, windows types, sheds, attics and basements. **For building scale calculations- only 50% of the slope area is included in the lot area calculation. Max Gross Floor Area- 9000sf - 0.4xlot area 9k to 18k sf - 3, xsf of lot area in excess of 9k. 9k to 18k sf -5, xsf of lot area in excess of 18k. *Basements, crawl spaces and subterranean garages are included in GFA (with notes), special inclusions are also noted for expanded window wells, walkout basement stairwells, accessory Walk-out basements- 40% of the total area of all portions of the finished floor that are enclosed by lines extending perpendicular from the basement wall facing the ravine to the opposite basement wall across the full width of the exposed portion of the basement wall at a height of two feet (2 ) above grade. The resulting square footage shall be included in the gross floor area of the bluff/ravine property. Permitted construction zone Any structures may be constructed in the Slope Transition Area: provided that the structure meets all zoning regulations and development guidelines, including engineering review; additional standards All construction activity prohibited within 20 of the ravine area and 50 from the bluff edge - except as may be necessary to provide site drainage needs City Eng approval. A temporary fence shall be erected along a line that is ten feet (10 ) from the top ravine edge or top bluff edge, or both, as the case may be, during any development or construction activity on bluff/

20 COMPARISON OF DRAINAGE AND GRADING REGULATIONS (continued) GLENCOE HIGHLAND PARK LAKE FOREST WINNETKA LAKE BLUFF INTERNATIONAL BUILDING CODE (2012) Construction permitted in steep slope zone The following structures may be built within the Steep Slope Zone: retaining walls and structures necessary for slope stabilization, structures on existing foundations, cantilevered structures less than 4, lifts, stairs, decks, walkways, fences, and boathouses (there are certain restrictions for each structure). Maintenance, drainage and landscaping standards included for steep slope zone Retaining walls for slope stabilization, structures on top of existing foundations, elevators, bridges, walkways, steps and fences that do not obstruct the flow of water and light, and utility service lines are permitted after review. Minimal site landscaping (grading and clearing & installing of landscaping) may be allowed within the bluff or ravine area, except within 20 and 50 of the ravine and bluff edge respectively. Within bluff/ravine area: -erosion control and slope stabilization activities -public utility and improvement projects - Drainage improvements that are necessary to prevent or mitigate erosion -General maintenance and landscaping, including the removal of diseased, dead, or damaged trees -Action necessary to remediate an unstable or unsecure slope that poses an imminent danger to persons or property No foundation may be built in any land from a 1:3.3 line delineated from the toe of the bluff to the horizontal. Submittal requirements As needed for permit issuance to comply with building code, zoning and all other ordinances; seal of an IL licensed structural or geotechnical engineer needed. As needed for building permit reviews. For subdivision or building permit review- All site information including topography, existing trees and vegetation, ravine and/ or bluff conditions (including establishment of the limits of the Ravine or Bluff Area), geological and soil conditions, proposed plans for landscaping and lawn installation, and such other information as may be deemed necessary. Plat of survey needed for permit application - Existing nonconforming A new structure may be built on the exact foundation of a nonconforming structure, provided that the rebuilt structure does not extend beyond the previous foundation or increase the bulk. Non-conforming structures may expand provided that the proposed construction does not increase nonconformity and conforms to all applicable zoning regulations, including steep slope. The Zoning Board of Appeals may consider variations for additions to non-conforming structures if proposed construction is less nonconforming than the existing residence and the ravine or bluff slope does not show any indication of instability. Non-conforming structures may expand provided that the proposed construction does not increase nonconformity and conforms to all applicable zoning regulations, including steep slope. Appeals Relief from Development Standards that cause practical difficulties, hardships or economic hardship may be appealed to Village Manager and ultimately the Village Board. The Zoning Board of Appeals may consider variations after receiving variations from the Natural Resources Commission The Zoning Board of Appeals may consider variations for new construction, additions, or new significant auxiliary buildings, under following findings Applicant must show that adequate toe of slope improvements exists and the entire slope shows no indication of instability. Any requested variation less than or equal to 25% of setback (i.e. encroachment of less than 10 into the 40 bluff setback), may be granted by the ZBA. Anything greater than 25% goes to Village Board after recommendation of ZBA.

21 COMPARISON OF DRAINAGE AND GRADING REGULATIONS GLENCOE HIGHLAND PARK LAKE FOREST WINNETKA LAKE BLUFF INTERNATIONAL BUILDING CODE (2012) Primary purpose Protect- bluff and ravine to avoid degradation Protect-individual property rights Public interest served by protection of people and property from potentially hazardous geological and hydrological conditions. The ravine and coastal steep slopes are an inherent natural resource which imparts a unique and substantial character. Erosion, slope failures, and loss of vegetation along one portion of a slope can have an adverse impact upon adjacent sloped areas. Because these areas may be abused so as to create conditions which jeopardize property values and the natural ecosystem, appropriate controls are necessary. (aesthetics and safety) Protect public and private property from damage or destruction resulting from the natural erosion processes occurring within the ravines and bluffs along the shore of Lake Michigan, or abnormal or accelerated ravine and bluff erosion resulting from land development and construction activities occurring on adjacent or nearby properties, and to protect the fragile ravine and bluff ecosystem from unwarranted damage or destruction caused by land development and construction activities. No steep slope ordinance. Only slope related note - When slopes are used to provide a transition between the existing grade and the proposed grade for the top of the permanent fill, or for the construction of a compensatory storage basin, those slopes will be limited to a maximum of 1:6, or 1 foot of vertical rise for every 6 feet of horizontal run. The Village of Lake Bluff s ravine and bluff areas, which are inherently fragile and subject to erosion due to glacially formed soils containing unstable sediment, rock, and silt, provide a unique natural resource to the Village and to its residents that must be preserved and protected. For slope protection (with respect to man-made slopes) to prevent soil erosion. Definition of steep Slope impact area- Line representing the intersection of table land and a 22 degree slope (2.5H:1V) extending upward from the toe of the bluff or ravine. Also includes area of the lot where the slope of the lot is steeper than 5.7 degrees (10H:1V). Not specifically defined, notes as area that has ravines and bluffs / exhibit steep slopes containing unstable sediment, rock and soils. RAVINE AREA- The Ravine Area shall include all property within or adjacent to a ravine beginning at the point of intersection of a line with the table land, said line extending from the toe of the slope upward at a vertical angle of twenty -two (22) degrees. Not defined. Not defined. Steep slope line- A line representing the intersection of the table land with a 27 degree slope (2H:1V) extending upward from the toe of the bluff or ravine. Steep Slope Zone- Area between steep slope line and the toe line. RAVINE EDGE - That point on the ravine side of the table land where the slope of the land first exceeds ten (10) percent. TABLE LAND - Land where the slope in any direction does not exceed ten (10) percent. Table Land- Land at top of bluff/ravine where slope is less than a 5.7 degree slope (10H:1V) Toe line- Land at bottom of bluff/ravine where slope is less than a 5.7 degree slope (10H:1V) TOE OF SLOPE - The toe of the ravine or bluff slope is that point in the ravine or bluff where the slope is less than twenty-two (22) degrees or where the slope reverses directions. On compound slopes where there may be more than one possible toe location, the controlling point shall be whichever toe location provides the greater ravine or bluff area.

22 COMPARISON OF DRAINAGE AND GRADING REGULATIONS (continued) GLENCOE HIGHLAND PARK LAKE FOREST WINNETKA LAKE BLUFF INTERNATIONAL BUILDING CODE (2012) Setbacks and setback from bluff As defined by slope impact area. No building construction 10 from top of ravine. 40 from top of bluff. Swimming pools prohibited within 10 of Steep Slope Zone. Accessory structures no greater than 150 sq/ft may be built within the Steep Slope Setback. Lifts, bridges, walkways, steps and fences may be built within steep slope No building construction allowed within 20 from top of ravine. 75 from top of bluff. The City Engineer may approve encroachments into the bluff or ravine setback area for the construction of landscape features, auxiliary buildings (slab foundation), bridges, wood decks or other similar facilities No principal structure may be constructed 10 from Top Ravine Edge. 40 from Top Bluff Edge. However, paths, steps, and benches are allowed to be located within a bluff or ravine. No swimming pool may be built within 20 from top edge of ravine and 40 from top edge of bluff. Decks may cantilever over bluff or ravine, provided that no pier foundations or supports are located within the bluff or ravine. H/2 but 2 min. and 20 max. from toe of slope. H/2 but 2 min. and 10 max. from top of slope. (J108.1) Accessory structures may be built within 10 from the Top Bluff Edge. The Village Engineer may approve certain other activities (erosion control and slope stabilization, public utility and other improvement projects, drainage improvements). FAR calculation All gross floor area calculations are based on lot size. *There are exclusions for certain square footage of garages, porches, unfinished and finished attics, undereaves, courtyards and basements. All FAR based on the lot area. Some overlay zones also apply to calculation. All max. square footage is based on lot size with exclusions for certain square footage of garages, porches, windows types, sheds, attics and basements. **For building scale calculations- only 50% of the slope area is included in the lot area calculation. Max Gross Floor Area- 9000sf - 0.4xlot area 9k to 18k sf - 3, xsf of lot area in excess of 9k. 9k to 18k sf -5, xsf of lot area in excess of 18k. *Basements, crawl spaces and subterranean garages are included in GFA (with notes), special inclusions are also noted for expanded window wells, walkout basement stairwells, accessory Walk-out basements- 40% of the total area of all portions of the finished floor that are enclosed by lines extending perpendicular from the basement wall facing the ravine to the opposite basement wall across the full width of the exposed portion of the basement wall at a height of two feet (2 ) above grade. The resulting square footage shall be included in the gross floor area of the bluff/ravine property. Permitted construction zone Any structures may be constructed in the Slope Transition Area: provided that the structure meets all zoning regulations and development guidelines, including engineering review; additional standards for retaining walls. All construction activity prohibited within 20 of the ravine area and 50 from the bluff edge - except as may be necessary to provide site drainage needs City Eng approval. A temporary fence shall be erected along a line that is ten feet (10 ) from the top ravine edge or top bluff edge, or both, as the case may be, during any development or construction activity on bluff/ ravine property.

23 COMPARISON OF DRAINAGE AND GRADING REGULATIONS (continued) GLENCOE HIGHLAND PARK LAKE FOREST WINNETKA LAKE BLUFF INTERNATIONAL BUILDING CODE (2012) Construction permitted in steep slope zone The following structures may be built within the Steep Slope Zone: retaining walls and structures necessary for slope stabilization, structures on existing foundations, cantilevered structures less than 4, lifts, stairs, decks, walkways, fences, and boathouses (there are certain restrictions for each structure). Maintenance, drainage and landscaping standards included for steep slope zone Retaining walls for slope stabilization, structures on top of existing foundations, elevators, bridges, walkways, steps and fences that do not obstruct the flow of water and light, and utility service lines are permitted after review. Minimal site landscaping (grading and clearing & installing of landscaping) may be allowed within the bluff or ravine area, except within 20 and 50 of the ravine and bluff edge respectively. Within bluff/ravine area: -erosion control and slope stabilization activities -public utility and improvement projects - Drainage improvements that are necessary to prevent or mitigate erosion -General maintenance and landscaping, including the removal of diseased, dead, or damaged trees -Action necessary to remediate an unstable or unsecure slope that poses an imminent danger to persons or property No foundation may be built in any land from a 1:3.3 line delineated from the toe of the bluff to the horizontal. Submittal requirements As needed for permit issuance to comply with building code, zoning and all other ordinances; seal of an IL licensed structural or geotechnical engineer needed. As needed for building permit reviews. For subdivision or building permit review- All site information including topography, existing trees and vegetation, ravine and/ or bluff conditions (including establishment of the limits of the Ravine or Bluff Area), geological and soil conditions, proposed plans for landscaping and lawn installation, and such other information as may be deemed necessary. Plat of survey needed for permit application - Existing nonconforming A new structure may be built on the exact foundation of a nonconforming structure, provided that the rebuilt structure does not extend beyond the previous foundation or increase the bulk. Non-conforming structures may expand provided that the proposed construction does not increase nonconformity and conforms to all applicable zoning regulations, including steep slope. The Zoning Board of Appeals may consider variations for additions to non-conforming structures if proposed construction is less nonconforming than the existing residence and the ravine or bluff slope does not show any indication of instability. Non-conforming structures may expand provided that the proposed construction does not increase nonconformity and conforms to all applicable zoning regulations, including steep slope. Appeals Relief from Development Standards that cause practical difficulties, hardships or economic hardship may be appealed to Village Manager and ultimately the Village Board. The Zoning Board of Appeals may consider variations after receiving variations from the Natural Resources Commission The Zoning Board of Appeals may consider variations for new construction, additions, or new significant auxiliary buildings, under following findings Applicant must show that adequate toe of slope improvements exists and the entire slope shows no indication of instability. Any requested variation less than or equal to 25% of setback (i.e. encroachment of less than 10 into the 40 bluff setback), may be granted by the ZBA. Anything greater than 25% goes to Village Board after recommendation of ZBA.