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HomeMy WebLinkAboutMINUTES - 03181997 - C87 TO: BOARD OF SUPERVISORS FROM: VAL ALEXEEFF, GMEDA DIRECTOR DATE: MARCH 11, 1997 SUBJECT: DESIGN STANDARDS FOR CREEKSME DEVELOPMENT SPECIFIC REQUEST(S)OR RECOMMENDATION(S)&BACKGROUND AND JUSTIFICATION I. Recommended Action: APPROVE in concept the following design standards for creekside development, PROVIDE staffwith direction and any changes to these design standards, REFER these design standards to the planning commissions, building industry and engineering community for comment and bring them back for formal Board approval with any recommendations from the planning commissions, building industry and engineering community. H. Financial Impact: No direct impact.\,,With complete information submitted early in the application process, there should be a cost savings to the County and the applicant as a result of more efficient processing. M. Reasons for Recommendations and Background: To protect the riparian habitat along creek corridors and to protect structures and property from damage due to creek bank failures, there is a structure setback requirement for any development along a creek. To determine the structure setback for a development, there are environmental criteria and engineering criteria that must be satisfied. The environmental criteria is designed to protect the riparian habitat of the creek and the engineering criteria is designed to protect the development structures from damage. Both the engineering and environmental criteria are applied to a development and the resultant structure setback line located farthest from the centerline of the creek would be the appropriate setback for the development. Continued on Attachment: X SIGNATURE: —RECOMMENDATION OF COUNTY ADMINISTRATOR _RECOMMENDATION OF BOARD COMMITTEE APPROVE OTHER SIGNATURE(S): Q ACTION OF BOARD ON MAR 18 1997 APPROVED AS RECOMMENDED_OTHER_ VO OF SUPERVISORS UNANIMOUS(ABSENT ) AYES: NOES: ABSENT: ABSTAIN: RMA:mw g:\engsvc\bo\crk-dvlp.G Originator:Public Works(EIS) Contact: Mitch Avalon(313-2371) 1 hereby certify that this is a true and correct copy of cc: P* Batchelor,County Administrator an action talmn and enured c:i 'he minutes of do J. Michael Walford,Public Works Director Board of Supetn H. Bragdon,Community Development Director ATTESTED.* �/j� F. Lew,Building Inspection Director PHIL BATCHELOR,Clerk of the board County Counsel fff BtIPMttM01a sm County AdmirdabaIN Flood Control SUBJECT: DESIGN STANDARDS FOR CREEKSIDE DEVELOPMENT DATE: MARCH 11, 1997 PAGE -2- III. Reasons for Recommendations and Background (continued): Many of the environmental criteria are found in the County General Plan. One of the policies in the General Plan requires a minimum setback of 100-feet along natural creeks and streams. The General Plan also includes implementation measures which require all proposed development plans to provide for a structure setback along natural creeks and streams, and a goal to review and revise the County Ordinance Code to provide for the protection and enhancement of water courses and riparian vegetation. It should be noted that the Federal Government has recently listed the red legged frog on the endangered species list. Since the red legged frog is found throughout the County, this may increase the width of the structure setback needed to protect the riparian habitat on some creeks. The engineering criteria for locating the structure setback line is contained in the County Ordinance Code. The formula outlined in the Code for locating the structure setback line was established with major channels and creeks in mind. Current practice, however, also applies this code section to small creeks and channels, which results in a very conservative structure setback location for these smaller creeks. The structure setback required by the code on a typical major creek that is 20-feet deep, for example, may be located approximately 80-feet from the creek centerline. This is calculated by determining where a line, beginning at the toe of the creek bank slope, with a slope of 2.5 horizontal to 1 vertical intersects the existing ground, and then adding 30-feet. This may be appropriate to protect structures on a major creek. For a small creek that is 4-feet deep, the setback calculated with the same formula may be approximately 40-feet from the creek centerline. This is an overly conservative setback needed to protect structures on a small creek. These proposed design standards have a tiered structure setback formula which provides a structure setback area commensurate with the size of the creek or channel. From time to time requests are received for exceptions to the structure setback requirements. There currently is no policy, however, for granting an exception. These design standards would provide for the consistent treatment of requests for exceptions. The Community Development Department, Public Works Department, and Building Inspection Department will recommend modifications to the County Ordinance Code consistent with these design standards once they have been reviewed by the Planning Commissions and approved by the Board. IV. Consequences of Negative Action: Unnecessarily wide engineering structure setbacks will continue to be required of development along minor creeks with a watershed area less than one square mile. There will also be no uniform policy on granting exceptions to the Ordinance Code for structure setbacks from creeks and the goals and implementation measures of the Conservation Element of the General Plan will not be fully realized. V. Exhibit: DESIGN STANDARDS FOR CREEKSIDE DEVELOPMENT 1. PURPOSE: Development projects on property adjacent to creeks should be developed to minimize the potential damage to property and structures as a result of creek bank failure, and should be developed to minimize impacts to any riparian vegetation in and along the creek. 2. SUBDIVISIONS: All tentative maps for projects located along creeks must show the structure setback line to protect the structure from creek bank failure and to protect the riparian vegetation along the creek as follows: SUBJECT: DESIGN STANDARDS FOR CREEKSIDE DEVELOPMENT DATE: MARCH 11, 1997 PAGE -3- A. STRUCTURE PROTECTION: Show the structure setback line on the tentative map in accordance with Section 914-14.012 of the County Subdivision Ordinance Code(Title 9). The location of the setback line may need to be verified by submittal of hydrologic and hydraulic calculations in addition to cross sections of the creek. Verification of the placement of the structure setback line will be made by the Public Works Department prior to a development application being accepted as complete for processing purposes. An exception to the above tentative map requirements may be allowed for large lot minor developments where the building envelopes are 100-feet or more from the centerline of the creek, or where the watercourse carries less than 2 cubic meters per second(approximately 70 cubic feet per second) of design storm flow. For all development, no structure setback lines are required to be shown for a drainage way that carries less than approximately 2 cubic meters per second of design storm flows. Structure setback lines for creeks that carry storm flows of over approximately 2 cubic meters per second of flow, up to creeks that carry storm flows from watersheds of up to one square mile in area, shall be located as described in the Ordinance Code except that the calculated slopes shall be at a 2 to 1 gradient (2 horizontal to 1 vertical) and the additional setback shall be 3 meters (approximately 10-feet) instead of 30-feet. Structure setback lines for creeks that drain watersheds over one square mile in area shall be located as described in the Ordinance Code (calculated slope gradient of 2'/z to 1, or water surface plus freeboard, plus 30-feet to 50-feet). B. RIPARIAN VEGETATION PROTECTION: Show the limits of riparian vegetation (e.g.: cattails and other hydrophytes, trees, etc.) along the creek. This limit line shall be shown on the tentative map and information shall be submitted to support the location of the limit line, such as aerial maps or site photographs showing the vegetation and canopy of the trees along the creek. Chapter 816-6, "Tree Protection and Preservation" has additional information requirements specifically for trees, such as tree surveys. Site plans shall also indicate where riparian vegetation may be damaged or removed by anticipated improvement within the creekbed. Verification of the limits of the riparian vegetation will be made by the Community Development Department prior to a development application being accepted as complete for processing purposes. C. STRUCTURE SETBACK LINE: The structure setback line applicable to the development shall be the more restrictive of the two determined above, that needed to protect the structure or that needed to protect the riparian vegetation. The structure setback line shall be shown on the parcel or final map and labeled "Creekside Structure Setback Line." The development rights to the area of the property between the creek and the structure setback line shall be dedicated to the County, or alternatively the area shall be designated on the map as "Restricted Development Area." 3. GRADING PERMITS, LAND USE PERMITS, DEVELOPMENT PLANS: All Grading Permit, Land Use Permit, or Development Plan Permit applications adjacent to a creek shall show any existing recorded structure setback line on the site plan. For permits with a structure located within 15 meters (approximately 50-feet) of the top of creek bank or drainage way, where a structure setback does not exist or is not required, the top of the bank shall be shown on the site plan and the depth of the creek or drainage way noted. For grading permits the top of creek bank shall be shown on the grading plan and the depth of the creek or drainage way noted. Site plans and grading plans shall show any proposed or existing drainage facilities or overside drains into the creek or drainage way, and any riparian vegetation in or along the creek or drainage way. SUBJECT: DESIGN STANDARDS FOR CREEKSIDE DEVELOPMENT DATE: MARCH 11, 1997 PAGE -4- 4. BUILDING PERMITS: All Building Permit applications adjacent to a creek shall show any existing recorded structure setback line on the site plan. For permits with a structure located within 15 meters (approximately 50-feet) of the top of creek bank or drainage way, where a structure setback does not exist or is not required, the top of the bank shall be shown on the site plan and the depth of the creek or drainage way noted. For structures located near the top of bank of a creek or drainage way, the foundation shall be designed and constructed to protect the structure against bank failure or erosion. Building Inspection Department may require special analysis to confirm.such performance will be achieved. Any existing or proposed drainage facilities or overside drains into the creek or drainage way, and any riparian vegetation in or along the creek or drainage way, shall be shown on the plans. 5. EXCEPTIONS: An exception to the requirements for structure setback and riparian corridor, as described in these design standards, the Ordinance Code and the General Plan, or a modification to an existing recorded structure setback may be allowed if the following can be satisfied: A. A geotechnical investigation is performed to analyze the relationship between the structure and the stability of the creek bank. The investigation should take into account soil saturation, ground water effects, surface water drainage patterns, creek flow velocities of the design storm, soil type, etc., and show the structure is safe from any effects of the creek. B. An analysis of the relationship between the structure and the creek flow. The analysis should determine if the flows are nonerosive for the soil type and if the structure will be above the water surface of the design storm plus freeboard, and if the structure will hinder or hang up the movement of any floating debris in a storm. C. There is no adverse impact to the riparian vegetation of the creek as determined by the Community Development Department. D. Execution and recordation of a release and indemnification agreement where the applicant holds the County harmless from any liability as a result of any damage to the structure and/or property due to creek bank erosion or failure, or from flood damage. A modification to an existing structure setback may be granted without any of the above geotechnical or hydraulic analysis, if the application for the modification complies with the other provisions of these design standards as outlined in Section 2 above. This provision for modification applies in those areas where the proposed encroachment is between the structure setback line established by these design standards and an existing structure setback line. Any approved modification will be formalized with the execution and recordation of a drainage permit and, if necessary, execution and recordation of a release and indemnification agreement where the applicant holds the County harmless from any liability as a result of any damage to the structure and/or property due to creek bank erosion or failure, or from flood damage. No roads or access shall be allowed in the structure setback area. An exception will be considered if. a) there is no other access to the property, b) the access is properly engineered to prevent damage from creek bank failure or erosion, and c) the riparian vegetation is not adversely impacted. s o q SUBJECT: DESIGN STANDARDS FOR CREEKSIDE DEVELOPMENT DATE: MARCH 11, 1997 PAGE -5- 6. APPEAL PROCEDURES: Only the approval bodies of the Planning Agency may grant an exception to the requirements of the Ordinance Code (and these design standards) to provide a structure setback along creeks and unimproved earth channels or an exception to the riparian corridor required in the County's General Plan (and these design standards). In granting such an exception to the structure setback requirement or riparian vegetation requirement, the approval body shall make the following two findings, in addition to the required findings of Chapter 92-6 of the Ordinance Code: A. That granting an exception to the structure setback requirement will not create the potential for damage to the proposed structures from the design storm. This finding should be based upon sound engineering criteria, such as cross sections of the creek, hydraulic data and geotechnical reports, that demonstrates the creek has a nonerosive bed and stable banks. B. That granting an exception to the structure setback requirement will not be detrimental to the environment or the riparian vegetation in the creek or unimproved earth channel. This finding should support the riparian vegetation and habitat goals and policies of the General Plan (policies 8-78 through 8-94 of the Conservation Element). Any request for an exception to the structure setback requirements shall be accompanied by suggested findings, and all documentation necessary to support the findings (cross sections, geotechnical reports, site plans, assessment of creek vegetation and habitat, etc.). The applicant shall submit the request, findings and documentation to the Director of Community Development, with a copy to the Public Works Department. 7. ALLOWABLE IMPROVEMENTS IN THE STRUCTURE SETBACK AREA: It is the intent of the Board to preserve habitat and to allow only those improvements in the structure setback area or riparian corridor that are necessary to protect the property, or are low cost improvements and are in keeping with the surrounding environment; and do not obstruct design storm flows. Only the following uses may be allowed within the structure setback area or riparian corridor of the creek: A. Landscaping. Landscaping in the riparian corridor must be native species consistent with those in the local creek habitat. B. Fencing. Fencing shall not be allowed to disrupt animal movement along the riparian corridor, and shall not be installed in that portion of the creek that contains the storm flows or where it would cause debris to hang up and restrict the creek flows. C. Ground level patios D. Low level decks E. Grading. Grading may be allowed above the creek bank. Any proposed grading must first be reviewed by the Community Development Department. • r, 4 • M f I ADDENDUM TO C.87, March 18, 1997 APPROVED the recommendations as set forth and further DIRECTED staff to meet with environmental groups and other interested parties to review the proposed design standards for creekside development and to return the design standards to the Board. ! i