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HomeMy WebLinkAboutORDINANCES - 05091989 - 89-28 /. 14b r ORDINANCE NO. 89- 28 (Drainage Facilities, Easements, Setbacks and Offsite Improvements for Subdivisions) The Contra Costa County Board of Supervisors ordains as follows (omitting the parenthetical footnotes from the official text of the enacted or amended provisions of the County Ordinance Code) : SECTION I . SUMMARY. This ordinance amends and updates the requirements for drainage facilities, easements and setbacks in connection with subdivisions approved by the County of Contra Costa. In addition, this ordinance adds certain requirements relating to the acquisition of property to construct or install offsite subdivision improvements. SECTION II. Section 94-4 .413 is added to the County Ordinance Code to read: 94-4 .413 Offsite improvements. Whenever improvements are required to be constructed outside of the subdivision, the sub- divider shall : ( 1 ) Furnish proof satisfactory to the public works department that the subdivider or county has sufficient title or interest in said property to permit the improvements to be made; or (2) If the public works .department determines that neither the subdivider, nor the county, has sufficient title or interest in said property, furnish all of the following: a . The names and addresses of the current owners of record of the property and a legal description (metes and bounds) and plat map (drawn to scale) of the property proposed to be acquired by' eminent domain. b. Proof satisfactory to the public works depart- ment of full compliance with the California Environmental Quality Act (Pub. Resources Code , § 21000 et seq. ) , Government Code sec- tion 65402 and the Relocation Assistance Act (Gov. Code, § 7260 et seq. ) in connection with the proposed acquisition. c . A current title report and appraisal of the prop- erty, in a form and by an appraiser approved by the public works department. d. A written statement of all offers made to obtain the property by negotiation and copies of all correspondence relating to offers and responses , including evidence of an offer which satisfies the requirements of Government Code. section 7267.2. e. A fully executed agreement , in a form approved by the county counsel , under which the subdivider agrees to pay all costs for acquisition of the property, to post a cash deposit and security bond in the amounts approved by the public works department and specified in the agreement and to comply with the agreement' s other terms. f. The cash deposit(s) and security bond required by the agreement. (Ord. 89- 28 ; Gov. Code , § 66462.5. ) ORDINANCE NO. 89- 28 M SECTION III. Division 914 of the County Ordinance Code is repealed, and re-enacted in amended form to read: DIVISION 914 DRAINAGE Chapters: 914-2 Minimum Requirements 914-4 Natural Watercourses 914-6 Open Channels and Ditches 914-8 Conduits 914-10 Levees 914-12 Detention Basins 914-14 Rights of Way and Setbacks 914-16 Miscellaneous Chapter 914-2 MINIMUM REQUIREMENTS Sections : 914-2.002 Onsite collect and convey requirements. 914-2.004 Offsite collect and convey requirements. 914-2.006 Storm water disposal restrictions. 1 914-2.008 Runoff quantity determination. 914-2.010 Drainage facilities - Minimum capacities. 914-2.002 Onsite collect and convey requirements. (a) All portions of the subdivision shall be protected from flood hazard, inundation, sheet overflow and ponding of storm waters, springs and all other surface waters. All finished floors shall be above the water surface of a one-hundred-year frequency storm runoff from the maximum potential development of the drainage basin or watershed . (b) All surface waters occurring within the subdivision, as well as all surface waters flowing into and/or through the sub- division, shall be collected and conveyed through the subdivision without damage to any improvement, building site or dwelling which may be constructed within the subdivision. (c) Storm drainage facilities within the subdivision shall be designed and constructed in compliance with the requirements of this title and with current ordinance specifications and design standards of the public works department, so as to adequately con- vey with sufficient freeboard the storm water runoff from the maximum potential development of the drainage basin or watershed. (d) As required by Section 94-4.214, the final map or parcel map shall include a dedication to the county or other public agency of land rights for construction, maintenance and operation of all necessary storm drainage and access facilities. The land rights shall conform with the width and other requirements of Chapter 914-14 . (Ords. 89- 28 , 78-5) . 914-2.004 Offsite collect and convey requirements. (a) All surface waters flowing from the subdivision in any form or manner shall be collected and conveyed without diversion or damage to any ORDINANCE NO. 89- 28 (p. 2) improvement, building or dwelling to a natural watercourse having a definable bed and banks, or to an existing public storm drainage facility having adequate capacity to its point of discharge into a natural watercourse, or the advisory agency, in its discretion, may require that flows from the subdivision be regulated so as not to exceed the capacity of watercourses downstream when considered with regard to the development potential of the drainage basin or watershed. (b) Storm drainage facilities outside the subdivision shall be designed and constructed in compliance with the requirements of this title and with current ordinance specifications and design standards of the public works department, so as to adequately con- vey with sufficient freeboard the storm water runoff from the maximum potential development of the drainage basin or watershed. (c) Wherever surface waters must be collected or conveyed beyond the boundaries of the subdivision in order to discharge into a natural watercourse or into an existing adequate public storm drainage facility, the subdivider shall comply with either subsection (d) , (e) or (f) of this section, prior to filing of the final map or parcel map. (d) The subdivider shall deposit with the public works depart- ment: ( i) a copy of a duly recorded conveyance from the adjacent property owners, in a form and content acceptable to the public works director, granting to the subdivider the land rights to construct, maintain and operate all necessary storm drainage and access facilities; and ( ii) a copy of a duly recorded offer of dedication from the adjacent property owners, in a form and con- tent acceptable to the public works director, offering to dedicate to the county or other public agency sufficient land rights for construction, maintenance and operation of all necessary storm drainage and access facilities. Such documents shall be obtained from all property owners between the boundaries of the subdivision and the point at which the surface waters will be discharged into a natural watercourse having definable bed and banks or an existing adequate public storm drainage facility. The land rights shall conform with the width and other requirements of Chapter 91414. (e) The subdivider shall deposit with the public works depart- ment a copy of a duly recorded drainage release from the adjacent property owners, in a form and content acceptable to the county counsel, accepting the flow of surface waters from the subdivision onto and over that property, without liability by the county for damages occurring therefrom. Such releases shall be obtained from all property owners between the boundaries of the subdivision and the point at which the surface waters will enter a natural water- course having definable bed and banks or an existing adequate public storm drainage facility. ( f) The subdivider shall present written evidence which proves to the satisfaction of the public works department that it is not feasible to obtain by negotiation from the adjacent property owners either a drainage release , or land rights, and shall comply with the requirements of Section 94-4 .413. The board, in its sole discretion, may then authorize the institution of condemnation proceedings to acquire the land rights at the subdivider' s expense. (Ords. 89-28 , 78-5 ; Gov. Code, § 66462.5) . 914-2.006 Storm water disposal restrictions . Storm waters flowing from the subdivision in any form or manner shall not be permitted to flow into any water conveyance facility of the Contra Costa Canal, nor into any other water conveyance or impounding facility for domestic water consumption. (Ords. 89-29 78-5) . 914-2.008 Runoff quantity determination. Runoff quantities shall be determined by methods consistent with current engineering practices using basic data supplied by the public works department for the frequency of the averae recurrence interval stipulated in Section 914-2.010. (Ords. 89-g 28 , 78-5) . ORDINANCE NO. 89- 28 (p. 3) 914-2.010 Drainage facilities - Minimum capacities. (a) Storm drainage facilities directly affecting the subdivision shall have the following minimum capacities: ( 1 ) Major drainage facilities (i .e. , those serving a watershed area four square miles or greater) shall have adequate capacity to contain with sufficient freeboard a 50-year frequency of average recurrence interval runoff and contain without freeboard a 100-year average recurrence interval runoff; (2) Secondary drainage facilities ( i .e. , those serving a watershed area one square mile or greater but less than four square miles) shall have adequace capacity to contain with suf- ficient freeboard a 25-year frequency of average recurrence inter- val runoff; (3) Minor drainage facilities ( i .e. , those serving a watershed area less than one square mile) shall have adequate capacity to contain with sufficient freeboard a 10-year frequency of average recurrence interval runoff; (b) As used in this division, the terms "storm drainage facil- ity" and "drainage facility" shall include, without limitation, channels, ditches , conduits (e.g. , pipes and culverts) , detention basins and all appurtenances. (Ords. 89-28 , 78-5) . Chapter 914-4 NATURAL WATERCOURSES Sections : 914-4 .002 Protection of natural watercourses . 914-4 .004 Watercourse capacity and stability analysis. 914-4 .006 Vegetation removal. 914-4.008 Side drainage. 914-4.002 Protection of natural watercourses. The advisory agency, in its sole discretion, may determine that a natural watercourse, or a substantial portion of a natural watercourse, is a scenic attraction or possesses significant riparian habitat, and may require that the watercourse or portion of the watercourse be protected in its natural state. The watercourse or portion required to be protected shall be referred to as a "protected watercourse. " (Ords. 89-28 , 78-5) . 914-4 .004 Watercourse capacity and stability analysis. Before a protected watercourse may be utilized for discharge of drainage flowing through or from a subdivision, the watercourse' s capacity and stability shall be substantiated through hydraulic calculations performed by a licensed engineer. Design flow volu- mes in excess of the watercourse's reasonable capacity shall be conveyed around the protected watercourse or shall be detained in adequate detention basins meeting the requirements of Chapter 914-12. Flow velocities in excess of those permitted by Section 914-6 .202 shall be attenuated using environmentally-sensitive techniques approved by the public works department. (Ord. 89- 28 . 914-4.006 Vegetation removal. Vegetation removal within a protected watercourse shall be restricted to the removal of downed trees, trees that are precariously undercut and trees that have the potential of creating a major obstruction within the floodway. Removal work shall be done in an environmentally-sensitive manner, so as to minimize damage to remaining trees, undergrowth and other riparian vegetation. Older trees requiring removal of dead or diseased limbs shall be trimmed under the supervision of a tree specialist. To the maximum extent possible, undergrowth shall be preserved . (Ord. 89- 28 ) . ORDINANCE NO. 89- 28 (p. 4) • 914-4.008 Side drainage. Storm drainage facilities discharging into a protected watercourse shall be designed in such a manner as to minimize visual impact and erosion within the pro- tected watercourse. Wherever possible, side drains shall be com- bined prior to discharging into the watercourse to reduce the number of outfalls into the watercourse. (Ord. 89- 28 ) . Chapter 914-6 OPEN CHANNELS AND DITCHES Article 914-6 .2 Earth and Lined Channels Sections: 914-6 .202 Earth channels - Maximum design velocities. 914-6 .204 Earth channels - Minimum velocities. 914-6 .206 Earth channels - Side slopes. 914-6 .208 Lined channels - Side slopes. 914-6 .210 Lined channels —Outlet velocity. Article 914-6 .4 Roadside Ditches Sections: 914-6 .402 Discharge to roadside ditches. 914-6 .404 Roadside ditch sections. 914-6 .406 Purpose of roadside ditches. 914-6 .408 Roadside ditch gradients. Article 914-6 .2 Earth and Lined Channels 914-6 .202 Earth channels - Maximum design velocities. Maximum design velocities for natural or improved earth channels shall be those specified by a licensed soil engineer in the soil report. The calculations shall be based upon the United States Department of Agriculture , Soil Conservation Service Tractive Force Method, or an alternative method approved by the public works department. (Orris. 89- 28 , 78-5) . 914-6 .204 Earth channels - Minimum velocities. Minimum velo- cities at design capacity for earth channels shall be three feet per second. (Ords. 89- 28 , 78-5) • 914-6 .206 Earth channels - Side slopes. Side slopes for improved earth channels shall be those specified by a licensed soil engineer, but in no instance shall side slopes be steeper than two horizontal to one vertical. (Ords. 89- 28 , 78-5) . 914-6 .208 Lined channels - Side slopes. Side slopes for lined channels shall be those specified by a licensed engineer and shall be based upon the data contained in a soil report prepared by a licensed soil engineer. The engineering calculations shall also indicate the structural integrity of the lining and any needed subdrainage. (Ords. 89- 28 ., 78-5) • 914-6 .210 Lined channels - Outlet velocity. Where the outlet velocity from a lined channel exceeds the maximum allowable velo- city for the earth channel receiving the flow, suitable protective works shall be constructed to dissipate the flow. At a minimum, the outlet end of the lined channel shall be protected by a cutoff wall and the placement of loose riprap. The protective works shall be those specified by a licensed engineer and shall be based on engineering calculations of allowable flow velocities. (Ords. 89- 28 , 78-5) . ORDINANCE NO. 89- 28 (p. 5) Article 914-6 .4 Roadside Ditches 914-6 .402 Discharge to roadside ditches. No' concentrated flow of storm waters from a subdivision shall be discharged into a roadside ditch. (Ords. 89- 28 , 78-5) . 914-6 .404 Roadside ditch sections. Roadside ditch sections shall be subject to the approval of the public works department as to shape , size, gradient, lining, and location within the road right-of-way, and shall have the required hydraulic capacity. (Ords. 89- 28 , 78-5) . 914-6 .406 Purpose of roadside ditches. Roadside ditches and gutters shall be provided to carry the drainage from the road and tributary lands without damage to the roadbed or abutting pro- perty. (Ords. 89- 28 , 78-5) . 914-6 .408 Roadside ditch gradients. The maximum gradient for earth roadside ditches shall not exceed four percent, nor be less than one percent. The minimum gradient for lined roadside ditches shall not be less than one percent. (Ords. 89-2_, 78-5) . Chapter 914-8 CONDUITS Sections: 914-8 .002 Closed conduits - Minimum size. 914-8 .004 Closed conduits - Minimum flow line. 914-8 .006 Closed conduits - Maximum velocity. 914-8 .008 Closed conduits - Outlet velocity. 914 .8.010 Piping requirements. 914-8 .012 Storm drain inlets. 914-8 .014 Closed conduits - Streets and channels. 914-8 .016 Drainage facilities - Freeboard. 914-8 .002 Closed conduits - Minimum size. Closed conduits, including under-driveway culverts and street-crossing culverts, shall be of a size adequate to carry the design flow, but shall not be smaller than eighteen inches inside diameter. (Ords. 89- 28 , 78-5) . 914-8 .004 Closed conduits - Minimum flow line. Minimum flow line gradients for closed conduits shall not be less than three one-thousandths (0.003) foot per foot. (Ords. 89- 28, 78-5) . 914-8 .006 Closed conduits - Maximum velocity. Closed con- duits shall not be designed to operate at high velocities when site conditions may yield an erosive bed load in the facility. (Ord. 89- 28 ) 914-8.008 Closed conduits - Outlet velocity. Where the outlet velocity from a closed conduit exceeds the maximum allowable velocity for the storm drainage facility receiving the flow, suitable protective works shall be constructed to dissipate the flow. At a minimum, the outlet end of the closed conduit shall be protected by a cutoff wall and the placement of loose riprap. The protective works shall be those specified by a licensed engineer and shall be based on engineering calculations of allowable flow velocities . (Ords. 89- 28 , 78-5) . 914-8.010 Piping requirements. All pipe or culverts intended for use within the roadway shall be of a class or gauge recom- mended by the manufacturer and approved by the public works ORDINANCE NO. 89- 2 (p. 6) department for the cover and service conditions required and shall provide a minimum service life of fifty years. Pipe or culverts for use outside the roadway may be of any approved type and strength to meet field conditions. Metal pipe shall not be used in arterial, thoroughfare or collector streets. Corrugated steel and aluminum pipe shall be bituminous coated unless the soil and drainage water have pH or resistivity values approved by the public works department. Additional protective coating or paving of metal pipes may be required for severe service conditions. The class or gauge of pipe or culvert proposed at each location shall be noted on the improvement plans. (Ords. 89-28 , 78-5) • 914-8.012 Storm drain inlets. Storm drain inlets shall be of a design approved by the public works department. Pipelines shall be aligned with the storm drain inlet in such a manner and direc- tion as not to cause a reversal of direction of the flow of the water and as not to enter through a corner of the inlet. (Ords. 89-28 , 78-5) . 914-8 .014 Closed -conduits - Streets and channels. Water within street areas shall be placed in closed conduits when the maximum depth of computed flow exceeds the capacity of the gutter or creates a traffic hazard or endangers property. Storm water in natural or improved earth channels shall be placed in closed con- duits or concrete lined channels, except where the quantity exceeds eighty cubic feet per second , or except as provided other- wise in Chapter 914-4. (Ords. 89-28 , 78-5) . 914-8.016 Drainage facilities - Freeboard. Storm drainage facilities shall allow for tidal action and flood stage where applicable. The hydraulic pressure elevation in any storm drainage facility shall be at least fifteen inches below the top of any inlet grate or manhole. (Ords. 89-28 , 78-5) . Chapter 914-10 LEVEES Sections : 914-10.002 Compliance requirements. 914-10. 004 Design and soil report. 914-10.006 Toe and slope requirements. 914-10 .008 Top width - Reclaimed lands and open channels. 914-10.010 Top width - Protection from surface waters. 914-10 .012 Degree of protection. 914-10.014 Approval of design and construction. 914-10.016 Control and maintenance . 914-10 .002 Compliance requirements. Adequate levees shall be provided in compliance with Section 914-2.002. (Ords. 89-28 , 78-5) . 914-10.004 Design and soil report. All levees in excess of three feet in height shall be designed by a licensed soil engineer and shall require the submittal of a soil report. (Ord. 89- 28 ) . 914-10.006 Toe and slope requirements. For levees used in combination with open channels and waterways , the toe of the levee on the water side shall be placed at least two feet back from the top of the bank of channel or waterway. Levee side slopes shall not be steeper than two horizontal to one vertical. (Ords. 89- 28 , 78-5) . ORDINANCE NO. 89- 28 (p. 7) r_ 914-10.008 Top width - Reclaimed lands and open channels. Top width of levees constructed for the protection of reclaimed lands or the containment of open channels shall not be less than eighteen feet. (Ords. 89- 289 78-5) . 914-10.010 Top width - Protection from surface waters. Top width of levees constructed for protection of any portion of the subdivision from surface waters shall not be less than five feet. (Ords. 89- 28 , 78-5) . 914-10 .012 Degree of protection. The degree of protection for which levees shall be designed shall be as follows: ( 1 ) For watercourses and channels, levees shall provide the degree of protection as specified in Section 914-2.002 and shall include no less than three feet of freeboard; (2) For those areas to be protected from waters of San Francisco Bay and San Pablo Bay from the southerly and westerly boundaries of Contra Costa County to the state highway bridge at Carquinez Strait, levees shall provide protection from tides and from -waves created by wind action. Tops of curbs shall not be lower than elevation 7 .5 U.S.G.S. datum; (3) Forthose areas to be protected from the waters of Carquinez Strait and Suisun Bay from the state highway bridge at Carquinez Strait to Simmons Point on Chipps Island, levees shall provide protection from tides, flood flows in the Sacramento and San Joaquin Rivers, and waves created by wind action. The basis for flood protection shall be the U.S. Army Corps of Engineers' standard project flood , approximately equivalent to a recurrence interval of two hundred years. Tops of curbs shall not be lower than elevation 8.5 U.S.G.S. datum; (4) For those areas within the delta area from Simmons Point on Chipps Island to the easterly boundaries of Contra Costa County, levees shall provide protection from tides, flood flows in the Sacramento and San Joaquin Rivers and all waterways tributary thereto, and waves created by wind action. The basis for flood protection shall be the U.S. Army Corps of Engineers' standard project flood, approximately equivalent to a recurrence interval of two hundred years. Tops of curbs shall not be lower than ele- vation 9 .5 U.S.G.S. datum. (Ords. 89- 28 , 78-5) . 914-10.014 Approval of design and construction. Approval of the design and construction of all levees within those areas described in Section 914-10.012 (2) , (3) and (4) , shall be obtained from the U.S. Army Corps of Engineers, California State Reclamation Board, San Francisco Bay Conservation and Development Commission, and any active operating local reclamation district within whose boundaries levees are to be constructed. (Ords. 89- 2 8 , 78-5) . 914-10.016 Control and maintenance. The jurisdiction for the control and maintenance of all required levees shall be deter- mined by the county, except as to areas where reclamation districts or districts with similar powers have such respon- sibilities, in which case the district having that responsibility shall present assurances satisfactory to the county that it has the necessary means and will perform the continued necessary main- tenance of those levees protecting the subdivision. (Ords. 89.28 , 78-5) . Chapter 914-12 DETENTION BASINS Sections: 914-12.002 Detention basins - Where permitted. 914-12.004 Detention basins - Capacity. ORDINANCE NO. 89- 28 (p. 8) f M 914-12.006 Detention basins - Design standards. 914-12.008 Detention basins - Joint use. 914-12.010 Detention basins - Maintenance. 914-12.012 Infiltration basins. 914-12.002 Detention basins - Where permitted. Detention basins may be utilized only if they are approved by the public works department and contain at least fifteen acre-feet of storage capacity to provide regional flow mitigation benefits, except that smaller detention basins may be permitted where it can be shown to the satisfaction of the public works department that the develop- ment of a regional basin is not practical and that a smaller detention basin can be permanently operated and maintained by a public entity in a cost-effective manner. (Ords. 89- 28, 78-5) . 914-12.004 Detention basins - Capacity. Detention basins shall be sized to provide the desired reduction in peak channel flows and to store with freeboard the design average recurrence interval runoff. Detention basins shall also be sized to contain without freeboard a 100-year average recurrence interval runoff, unless it can be shown that a 100-year average recurrence interval runoff can be safely passed through the detention basin without damage to the detention basin or any other property. (Ord. 89-28 ) . 914-12.006 Detention basins - Design standards. (a) The design of a detention basin shall comply with the requirements of the State of California, Division of Dam Safety. (b) Detention basin side slopes shall be determined by a licensed soil engineer and presented in a soil report and in no case shall the side slopes of non-natural slopes be steeper than four horizontal to one vertical. (c) Detention basins and their appurtenant facilities shall conform with current design standards of the public works depart- ment. (Ord. 89-28 ) . 914-12.008 Detention basins - Joint use. A detention basin facility shall be used for no purpose other than drainage or flood control without the written approval of the public works depart- ment and the execution of a joint use agreement in a form approved by the county counsel . (Ord. 89-28 ) . 914-12.010 Detention basins - Maintenance. The subdivider shall insure the maintenance of a detention basin facility through either an existing public maintenance entity or by the creation of a public maintenance entity. The entity shall have an adequate revenue source to assure perpetual maintenance. (Ord. 89- 210 . 914-12.012 Infiltration basins . Infiltration basins shall not be permitted. Ord. 89-2.8_) . Chapter 914-14 RIGHTS OF WAY AND SETBACKS Sections : 914-14.002 Easements - General requirements. 914-14.004 Closed conduits - Minimum widths of easements. 914-14 .006 Open channels - Minimum widths of easements. 914-14.008 Ingress easements. 914-14 .010 Structures and encroachments within easements. ORDINANCE NO. 89- 2_ (p. 9) 914-14.012 Structure setback lines for unimproved earth channels. 914-14.014 Structures and encroachments within structure set- back areas. 914-14.016 Rights of way for levees and detention basins. 914-14.018 Joint use of rights of way. 914-14.020 Private drainage systems. 914-14.002 Easements - General requirements. Easements shall provide sufficient land rights for construction, maintenance and operation of drainage and access facilities. Easement widths shall be rounded up to the nearest foot. Easements shall not be divided longitudinally by lot lines. All easements shall be pro- vided with access to a public way, which access shall be usable by vehicular maintenance equipment. Where trees within an easement area are to remain, adequate additional easement width shall be provided. (Ords. 89- 28 , 85-40 § 3, 78-5. ) 914-14 .004 Closed conduits - Minimum widths of easements. Minimum widths of easements for closed conduits shall be equal to the outside diameter or width of the conduit plus three feet on each side, but in no location less than ten feet. If an easement is dedicated or granted to provide for the future construction of a closed conduit, the easement width shall include an additional twenty-five feet for construction purposes. (Ords. 89- 28, 85-40 § 3, 78-5) . 914-14. 006 Open channels - Minimum widths of easements. (a) For lined channels having a top width less than three feet, the minimum widths of easements shall be ten feet. For excavated earth channels and channels having a top width of three feet or greater that are lined with concrete or other materials, the mini- mum widths of easements shall contain the full outside top width of channel, including lining and the following additional widths: ( 1 ) Earth and rock lined channels Channel Top Width (Feet) Additional Width (Feet) 0-10 6 one side , 12 other side 11-30 6 one side, 15 other side 31-40 6 one side, 18 other side 41-50 6 one side, 21 other side 51-60 15 each side 61-70 18 each side 71 and above 21 each side (2) Concrete lined channels Channel Top Width (Feet) Additional Width (Feet) 3-10 3 one side, 10 other side 11-15 6 one side, 12 other side 16-30 6 one side, 15 other side 31-40 6 one side, 18 other side 41-50 6 one side, 21 other side 51 and above same as earth channels (Ords. 89-28 , 85-40 § 49 78-5) . 914-14 .008 Ingress easements. Where a channel or conduit does not have direct access to a public way, an ingress easement shall be provided. Ingress shall be provided within five hundred feet of the upstream and downstream ends of the channel or conduit and shall be spaced no more than 1500 feet apart. The minimum width of the ingress easement shall be twelve feet. Minimum radius of centerline of such easements shall be forty feet. ORDINANCE NO. 89- 28 (p. 10) s . ' Ingress easements shall be graded in such a manner so as to be . usable by vehicular maintenance equipment, but they need not be surfaced. (Ords. 89-28 , 85-40 § 4, 78-5) . 914-14 .010 Structures and encroachments within easements. No permanent structures of any kind other than drainage structures may be constructed within or over any easement described in this chapter. Encroachments such as filled slopes, retaining walls, fencing and landscaping shall not be permitted . Public utilities may be installed within easements upon approval by the public works department. (Ords. 89- 28, 85-40 § 4, 78-5) . 914-14 .012 Structure setback lines for unimproved earth channels. a "Structure setback line" means the line separating the structure setback area from the remainder of the lot. For unimproved earth channels within the subdivision, a structure set- back line shall be shown on the final map or parcel map as follows : The thread of the channel shall be shown as accurately as possible, and a dashed line shall indicate the appropriate set- back with a note describing the method used to determine the top of bank, selected from those set forth herein. The development rights for that portion of the lot on the creek side of the set- back line, which is defined as the "structure setback area," shall be offered for dedication to Contra Costa County by separate instrument. (b) "Top of bank" means the point where the water surface plus sufficient freeboard for the design average recurrence inter- val runoff intersects the existing ground, or the point where a line with a slope of 2.5 horizontal to 1 vertical extending from the toe of the channel intersects the , existing ground, whichever point is the greatest vertical distance above the channel invert. A separate top of bank shall be determined for each side of the channel. (c) The structure setback line for unimproved channels shall be determined by measuring the following horizontal distance away from the top of bank on each side of the watercourse: Height of top of bank Horizontal distance between above channel invert top of bank and setback line less than 201 301 201 - 29 .991 351 301 - 39 .99 ' 401 401 - 49 .991 451 501 and greater 501 (d) Where significant riparian vegetation exists beyond the limits required above, the advisory agency may extend the setback line to include such areas . (Ords. 89- 28 , 85-40 § 6 , 78-5) . 914-14 .014 Structures and encroachments within structure setback areas. No permanent structures of any kind other than drainage structures may be constructed within, under or over any structure setback area described in this chapter. Fencing and landscaping, including trees and shrubs, are excluded from this restriction. The structure setback line shall be verified prior to the issuance of a building permit. (Ords. 89-28 , 85-40 §§ 8 , 9 . ) 914-14 .016 Rights of way for levees and detention basins. All levees and detention basins shall be completely contained within a fee title land right held by, or dedicated to, Contra Costa County or other public agency. The right of way conveyed to the county or other public agency shall include adequate access and maintenance areas , as determined by the public works depart- ment. (Ords. 89-28 , 78-5) . 914-14 .018 Joint use of rights of way. The joint use of rights of way held by Contra Costa County or other designated public agency is not permitted without the written approval of the public works department and the execution of a joint use agreement in a form approved by the county counsel. (Ord. 89-28 ) . ORDINANCE NO. 89- 28 (p. 11 ) 914-14 .020 Private drainage systems. Slope intercept ditches , yard drains and other similar drainage systems are con- sidered private systems and land rights for such systems shall not be offered or granted to Contra Costa County. The subdivider or property owner shall be responsible for the maintenance of such private systems. (Ord. 89- 28 ) . Chapter 914-16 MISCELLANEOUS Sections: 914-16.002 Subdrainage - Where required. 914-16.002 Subdrainage - Where required. Subdrain facilities shall be provided where specified by the soil engineer controlling the work and other areas where deemed necessary by the county to prevent sliding or settlement of the earth surface . Facilities will be required to convey the Subdrainage to an approved point of discharge . The subdivider or property owner shall be responsible for the maintenance of subdrain facilities. (Ords. 89- 28 , 78-5) . SECTION IV. EFFECTIVE DATE. This ordinance becomes effective 30 days after passage, and within 15 days after passage shall be published once with the names of the supervisors voting for and against it in the CONTRA COSTA TIMES , a newspaper published in this County. PASSED ON May 9, 1989 by the following vote: AYES: Supervisors Powers, Fanden, Schroder, McPeak and Torlakson NOES: None ABSENT: None ABSTAIN: None ATTEST: PHIL BATCHELOR, Clerk of the Bo rd a d County Administrator Dep ty Board Chair [SEAL] DFS: tb (3-17-89) ORDINANCE NO. 89- 28 (p. 12)