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A. Public Streets Generally.
1. The subdivider shall provide a comprehensive trafficway system, designed and constructed in accordance with these criteria, applicable standards and ordinances, and the city of Chico general plan. Design of streets shall provide for safe vehicular operation at a specified design speed.
2. Public streets shall be required when the street is shown as an arterial or collector street on a master street and highway plan, the general plan, or any other specific or precise plan; or when the street will be used by the general public as a through access route; or when a public street is necessary for special needs including, but not limited to, bus routes, public service access, bike routes and pedestrian access.
B. Street Layout.
1. Existing Streets and Unsubdivided Land. Streets shall be laid out to complement the alignment of existing streets in adjoining subdivisions and to provide a logical continuation of existing streets where the adjoining land is not subdivided.
The advisory agency may require the realignment of streets in contemplation of the development or use of adjoining property and may require the provision of streets or dead-end street extensions to facilitate the subdivision of adjoining property.
Permanently dead-ended streets without cul-de-sacs shall not be approved. When a temporarily dead-ended street is extended to the boundary of the subdivision, a one-foot fee simple strip the width of the street right-of-way shall be dedicated to the city at the end of the street. A barricade, or temporary turning area, or temporary connection to another street shall be required for any such street.
2. Provision for Resubdivision. Where property is subdivided into lots substantially larger than the minimum size required by the zoning districts in which the subdivision is located, the advisory agency may require that streets and lots be laid out so as to permit future resubdivision in accordance with the provisions of these regulations.
3. Future Streets. Where determined necessary for the protection of the public welfare or substantial property rights, the advisory agency may require or approve the reservation of streets within a proposed subdivision for future public use; provided, that all land so reserved shall be dedicated in fee simple to the city.
4. Streets Parallel to Rights-of-Way. Where a subdivision borders on or contains a railroad right-of-way, canal, or limited access highway right-of-way, the advisory agency may require a street approximately parallel to such right-of-way at a distance suitable for the appropriate use of the intervening land. Such distance shall be determined with due regard for the requirements of approach grades and future grade separations.
5. Local Streets. Local streets shall be designed so that their use by through traffic will be discouraged. Excessively long, straight residential streets, conducive to high-speed traffic, shall not be approved.
C. Street Names. Proposed street names shall not be similar to present street names, except that streets that are a prolongation or approximate prolongation of existing streets shall be given the same names as the existing streets. No street shall be designated by the same name as any other street even though differentiated by a suffix (avenue, boulevard, way, place or other term), except that a frontage road shall be given the same name as the street on which it borders. Generally no street should change direction by more than 90 degrees without a change in street name.
All proposed street names must be approved by the city fire chief and the Butte County street coordinator.
D. Horizontal Alignment.
1. Specific Requirements. The criteria for the following design elements for each functional street classification shall be as set forth in Table 1:
a. Minimum design speed;
b. Minimum curve radius at centerline;
c. Minimum length of tangent between reversing curves; reversing curves without an intervening tangent shall not be permitted;
d. Minimum stopping sight distance at the given design speed.
2. Superelevation. Superelevations other than those set forth in the standard plans will be acceptable only in extraordinary circumstances and will be designed on an individual basis.
E. Profile.
1. Profile Generally. The grade line should coincide with the centerline of the street. To improve appearances and to reduce the number of sight distance restrictions, vertical curves should, when possible, be superimposed on horizontal curves. For safety reasons, the horizontal curve should lead the vertical curve. Sharp horizontal curves shall not be introduced at or near a pronounced grade sag or summit.
2. Minimum Grade. Minimum grades for all streets with paved gutters shall be 0.25%. Streets with unpaved gutters shall have a minimum grade along centerline of 0.50%.
3. Maximum Grades. Maximum grades shall be 6% for arterial and collector streets and 8% for local streets. A maximum grade of 4% is desirable whenever possible, especially at intersections.
4. Vertical Curves. Parabolic vertical curves shall be used when the algebraic difference in grade is greater than 1.0%. The criteria for the following design elements for each functional street classification and its corresponding minimum design speed shall be as set forth in Table 2:
a. Minimum length of vertical curve;
b. Minimum stopping sight distance;
c. Minimum passing sight distance;
d. Maximum rate of change of grade in percent per 100 feet at the minimum stopping sight distance. This criteria may dictate a vertical curve longer than the minimum stated in this section.
F. Cross Section.
1. Geometric Cross Section. Standard widths for street geometric cross sections shall be as set forth in the improvement standards.
Subdividers of subdivisions with five (5) or more lots shall be required to install full improvements on existing streets adjacent to the subdivision in accordance with the limits of construction required by the improvement standards. In the event that the subdivision will generate sufficient vehicular traffic to require additional traffic lanes or street extensions, the subdivider may be required to provide and improve these facilities.
Subdividers of subdivisions having fewer than five (5) lots shall be required to install full improvements on existing streets adjacent to the subdivisions from the subdivision property line to the existing edge of street pavement, or beyond as may be needed to maintain a maximum five percent (5%) shoulder cross slope, in accordance with the improvement standards.
2. Structural Section. The subdivider’s engineer shall prepare a soils report and determine the R value of the proposed subgrade material. Minimum structural section thicknesses shall be as set forth in the improvement standards. These minimums are based upon a subgrade material having an R value of 25 or more. If the R value is less than 25, the structural section shall be increase accordingly.
The director will determine the traffic index and, if needed, will require an increase in the structural section. Pavement structural section design shall be in accordance with the methods shown in the Highway Design Manual.
3. Curb and Gutter. Curb and gutter shall be installed adjacent to streets in all subdivisions and shall be constructed in accordance with the improvement standards.
4. Sidewalks. Sidewalks shall be installed within all streets in all subdivisions and shall be constructed in accordance with the improvement standards. Sidewalks shall be separated from the adjacent curb and gutter by a parkway unless a contiguous sidewalk is specifically approved to save trees or to conform to an existing contiguous sidewalk configuration. All sidewalks shall be installed within the public right-of-way.
The advisory agency may require the installation of sidewalks outside of the subdivision to maintain continuity of pedestrian access from the subdivision to other areas in the immediate vicinity.
5. Half-streets. Half-streets shall not be approved.
G. Intersections.
1. Intersections Generally. The criteria for intersections set forth in this subsection shall be minimum requirements. Based upon traffic analysis, the director may require additional features such as speed change lanes, tapers, separate turning lanes, refuse areas and traffic-control devices. Intersections with more than four approaches shall not be approved.
2. Intersection Spacing. Intersection spacing shall be determined in accordance with these criteria and those set forth in subsection B above, entitled “Street Layout.”
Maximum spacing between intersections shall be 1320 feet.
Minimum spacing of intersections shall be as follows:
a. Local streets, 250 feet;
b. Collector streets, 300 feet;
c. Arterial streets, 500 feet.
3. Geometrics.
a. Alignment. A secondary street shall intersect a primary street at right angles (radial when the primary street is curved). The secondary street alignment shall be perpendicular to the primary street from the centerline of the primary street to the end of the curb return on the secondary street.
b. Cross-Slope in Intersections. The criteria for treatment of cross-slope in intersection areas shall be as set forth in Figure 2.
c. Curb Returns. The standard curb return radius shall be 30 feet, measured to the face of curb.
d. Handicapped Ramp. The standard handicapped ramp shown in the improvement standards shall be installed at all curb returns.
H. Cul-de-Sacs. Cul-de-sac streets shall not exceed 500 feet in length.
The advisory agency may require reduced length, or may require the elimination of a proposed cul-de-sac in order to provide for the efficient circulation of traffic, the future development of the neighborhood street system, or the deployment of emergency services.
Cul-de-sacs shall be constructed in conformance with the improvement standards.
I. Access.
1. General. Street access control may be required by permitting ingress and egress only at specific locations determined by the advisory agency.
Access to arterial streets shall, in general, be permitted at intersections only. The advisory agency may require installation of backup (reverse frontage) lots, or side-on lots adjacent to arterial streets.
Access to other than arterial streets shall, in general, be limited to one opening per lot.
Access to the subdivision from adjacent streets shall be designed to utilize the most efficient circulation pattern within the subdivision.
2. Driveways. Driveways shall be constructed in accordance with the improvement standards.
J. Traffic Control and Safety Devices and Street Name Signs. Traffic control and safety devices shall be installed on all streets as required by the improvement standards and the public works director in order to promote traffic control and safety. Traffic control and safety devices shall include but not be limited to regulatory signs, warning signs, guide markers, construction signs, pavement markings, lane delineations and traffic signals. Street name signs shall be installed at all public, private and public/private intersections in accordance with the improvement standards.
K. Street Lights. City-owned street lights shall be installed on all public streets in accordance with the improvement standards. Street light spacing shall be as required by the public works director.
L. House Numbers. House and unit numbers shall be assigned by the building official and shall be placed and maintained in a manner which is clearly visible from the street.
(Res. No. 9 77-78 (part), Res. No. 57 82-83 §4, Res. No. 110 86-87 §§3-4, Res. No. 59 90-91 §§2-6, Res. No. 167 92-93 §1, Res. No. 113-07, Res. No. 19-13)
A. Alleys. Alleys may be required as part of a subdivision circulation system.
Alleys shall be constructed in accordance with the improvement standards.
Intersections of two alleys will be discouraged but may be acceptable in special instances.
B. Bicycle Paths, Pedestrian Ways and Equestrian Ways.
1. Generally. Bicycle paths, pedestrian ways, and equestrian ways may be required in conformance with an established city-wide plan or as required by the advisory agency. Design of said ways and paths shall be consistent with the principle of keeping separation between motorized vehicular traffic and other modes of traffic.
2. Bicycle Paths. Bicycle paths shall be constructed in accordance with the improvement standards. Recommended geometric criteria shall be as follows:
a. Design speed, 20 mph;
b. Sight distance, 120 feet;
c. Minimum curve radius, 65 feet;
d. Overhead clearance, 8 feet;
e. Maximum grade, 5%.
Adequate access points and bicycle parking facilities shall be provided as necessary.
Bicycle stands conforming with the improvement standards shall be provided at parking facilities.
3. Pedestrian Ways. In addition to sidewalk required adjacent to public roadways, pedestrian ways may be required where needed for traffic safety; and access to schools, playgrounds, shopping facilities, or other community facilities. The required width and location shall be as determined by the advisory agency.
4. Equestrian Ways. The minimum required typical section shall be as shown in the improvement standards. Minimum vertical clearance shall be 10 feet.
(Res. No. 9 77-78)
A. Private Streets Generally. Private streets may be permitted subject to compliance with the following design criteria and improvement standards of this chapter, Title 18 of this code, and Standard Plan No. S-18F.
B. Private Street Length.
1. Cul-de-sacs. Private street cul-de-sacs shall not exceed 500 feet in length.
2. Loop Streets. Private loop streets improved to the standards set forth in this section shall not exceed 1,000 feet in length.
3. Standards for private streets exceeding 1,000 feet in length shall be determined on a case-by-case basis.
C. Horizontal Alignment. Private streets shall conform to the following minimum standards:
1. Minimum curve radius at centerline shall be 50 feet.
2. Minimum cul-de-sac or turnaround radius to face of curb shall be 46 feet.
D. Profile. The maximum grade for a private street shall not exceed 8%. The minimum grade shall correspond to the standards for a public street.
E. Cross Section.
1. Geometric cross section.
a. Private streets servicing less than 26 lots shall have a minimum street width of 24 feet without on-street parking and 36 feet with on-street parking.
b. Private streets serving 26 lots or more shall have a minimum street width of 30 feet without on-street parking and 40 feet with on-street parking.
c. Private streets may be either crowned streets or valley gutter streets. Valley gutters shall not be used on streets serving 26 lots or more.
2. Curb and Gutter.
a. Crowned Streets. Curb and gutter shall be constructed in accordance with city of Chico public street improvement standards.
b. Valley Gutter Streets. Curb and gutter may be constructed in accordance with the public street improvement standards, or curbing with a minimum width of 6 inches above the surfaced section of the private street at the curb line may be constructed. A 4-foot wide longitudinal P.C.C. valley gutter shall be constructed along the street centerline when the slope is less than 1%.
3. Structural Section. The subdivider’s engineer shall prepare a soils report and determine the “R” value. If the “R” value is 25 or more, the minimum structural section shall consist of four inches of compacted aggregate base with a one and one-half inch asphalt concrete overlay, or an equivalent full depth asphalt section as approved by the public works director. If the “R” value is less than 25, the structural section shall be as determined by the public works director.
F. Intersection with Public Street.
1. A private street shall intersect a public street at right angles.
2. Private streets shall have standard driveway approaches installed at intersections with public streets, unless curb returns are authorized by the public works director.
G. Sidewalks. Pedestrian access shall be provided either by constructing sidewalks in accordance with the design criteria, or pedestrian access may be provided by a comprehensive on-site pedestrian access system approved as part of a subdivision, zoning or permit approval.
H. Street Lights. Street lights shall be installed as required by the public works director.
I. Street Names. Proposed street names shall not be similar to present street names, except that streets that are a prolongation or approximate prolongation of existing streets shall be given the same names as the existing streets. No street shall be designated by the same name as any other street even though differentiated by a suffix (Terrace, Court, Lane, Place, or other term). Generally, no street should change direction by more than 90 degrees without a change in street name. Private street names shall be suffixed “Terrace,” “Court,” “Lane,” or “Place.”
J. Signs. Street signs shall be installed at all street intersections in accordance with city of Chico public street improvement standards. The street sign shall clearly indicate that the street is a private street. Stop signs shall be installed on all private streets that intersect a public street.
J. House Numbers. House and unit numbers shall be assigned by the building official and shall be placed and maintained in a manner which is clearly visible from the street.
L. Parking.
1. All private streets approved for no on-street parking shall be signed for “NO PARKING” and all curbs within 15 feet of any fire hydrant shall be painted red.
2. All private streets providing emergency vehicle access shall provide additional signage and markings as directed by the fire chief and chief of police.
3. All development utilizing private streets without on-street parking shall provide off-street parking in the amount specified in Title 19 of this code plus two (2) additional spaces for each residential unit.
4. At the time the private street is created, a statement shall be included in the conditions, covenants and restrictions or other recorded document approved by the city attorney that sets forth the following:
a. On-street parking is prohibited on private streets (if appropriate).
b. The California Vehicle Code does not apply to routine traffic matters on private streets.
c. The city of Chico police department does not enforce or respond to routine traffic matters on private streets.
M. Setbacks. On any lot abutting a private street, any setback required by this code shall be measured from the edge of the private street easement.
N. Private Street Maintenance. Whenever private streets are approved for a residential subdivision, the developer or subdivider through recorded conditions, covenants and restrictions, or other instrument approved by the city attorney shall provide for the following:
1. Maintenance of the private street and related private facilities, including but not limited to the following:
a. Street;
b. Street lights;
c. Traffic-control devices, if any;
d. Sanitary sewer facilities;
e. Storm drainage facilities.
2. If the private street and related private facilities are not adequately maintained, the city, after prior notice to the organization responsible for maintenance and property owners, shall have the right to:
a. Enter upon and maintain and repair the facilities, and to recover the prorata costs of such maintenance or repairs from each owner of a lot having access to a private street or utilizing private facilities, which costs shall constitute a lien upon the lot until paid; and/or
b. Form a maintenance district or benefit assessment district to provide for the maintenance of such private streets or facilities.
3. A private homeowners’ association shall be formed to maintain all private streets and other related private facilities whenever conditions, covenants and restrictions are prepared for a residential subdivision containing five or more lots.
(Res. No. 110 86-87 §5, Res. No. 22 88-89, Res. No. 59 90-91 §§6-7, Res. No. 67 90-91, Res. No. 167 92- 93 §2, Res. No. 113-07)
The subdivider may be required to provide major structures such as retaining walls, bridges or dams. Each structure shall be designed and approved on an individual basis. The subdivider shall provide the city with all engineering calculations used in the design of a major structure.
(Res. No. 9 77-78 (part))
A. General Requirements. The subdivider shall provide storm drainage facilities that will convey stormwater runoff, whether originating within the subdivision or in adjacent areas, to an existing drainage channel or drainage system. Adequate access for maintenance of the system shall be provided. The capacity of an existing drainage system must be large enough to accommodate the additional runoff generated by the subdivision. Drainage patterns existing prior to construction of the subdivision shall be maintained, and full consideration must be given to the rights of adjacent property owners with regard to surface water drainage.
The city will determine the capacity of an existing storm drain system.
The subdivider’s engineer shall prepare an analysis and design of the proposed storm drainage system. When stage construction is proposed, the analysis shall provide for the design of the entire storm drainage system.
The analysis shall consider all existing and future contributory drainage area, regardless of whether or not said area is in the subdivision.
The preliminary analysis shall accompany the tentative map.
B. Hydrology.
1. Storm Runoff. Runoff shall be computed by the rational method.
(Q = CIA) where:
Q = rate of runoff in cfs
C = coefficient of runoff
I = intensity of rainfall in inches/hr during the time of concentration tc (min.) – the elapsed time between the beginning of the storm and peak flow at the drainage structure
A = drainage area, acres
Computations should be clear and complete with all assumptions clearly stated. In making such computations, the following information shall be used:
a. Coefficient of Runoff. Typical values for runoff coefficients are set forth in Table 3.
b. Intensity of Rainfall. A rainfall intensity versus duration design chart for the Chico area is shown on Table 4. A minimum time of concentration of 10 minutes should be used whenever computations indicate a shorter time. For urban area drainage, the maximum initial time of concentration to the first drainage facility shall be 20 minutes. For unimproved areas, drainage time of concentration shall be determined by the method shown for small basins in the Highway Design Manual. The method of computation of time of concentration should be clearly indicated.
c. Design Storm Frequency. The design storm frequency shall be as follows:
(1) Bridges, 200 years;
(2) Open channels, 10 years;
(3) Culverts, 10 years;
(4) Major outfall lines, 10 years;
(5) Collector lines, 5 years;
(6) Local lines, 2 years.
A minimum freeboard of three feet shall be provided for bridges and box culverts, two feet for open channels, and one foot for storm drainage pipe inlets and outlets.
C. Roadway Drainage.
1. Grade. The minimum grade for side ditches and gutters will be 0.25% if paved, 0.50% if earth.
2. Limits of Flooding. Street drainage facilities shall be designed to keep flooding within six (6) feet of the face of curb for a design storm frequency of two (2) years for local streets and ten (10) years for all other streets. The depth of flow at gutter flow line shall not exceed 0.25 feet.
Concentrated flow across the traveled way is prohibited.
D. Conduit Design.
1. Type. For storm drain systems, circular pipes of reinforced concrete or cast-in- place concrete may be used. Class II pipe shall be the minimum for nonroadway areas. The minimum required strength for all pipe in the roadway area shall be Class III as designated by ASTM Specification C-76.
Culverts may be of any of the above materials in any standard manufactured shape. Reinforced concrete box culverts, if used shall be constructed in accordance with state standard plans.
2. Size. Pipes shall have a minimum diameter of 10 inches. For flows exceeding the capacity of 54-inch diameter pipe, open channels meeting the requirements of subsection H below may be acceptable.
3. Slope. Slope will be controlled by physical conditions and velocity criteria. Abrupt changes in slope are undesirable and are to be avoided wherever possible.
4. Velocity. Minimum velocity at full flow shall be two (2) feet per second (fps). The maximum velocity for storm drains shall be critical velocity at full flow. Culverts may have velocities greater than critical provided full consideration is given to the effects of abrasion.
5. Head and Head Losses. To facilitate the passage of debris and detritus, storm drains shall, unless otherwise approved, be designed to pass the design flow with a free water surface. Culverts shall be designed to provide a minimum freeboard of one foot from top of culvert to top of ditch bank at the entrance and exit points.
6. Roughness Coefficient. Suggested values for Manning’s roughness coefficient (n) are:
Reinforced concrete pipe . . . . . .0.012
Cast-in-place concrete pipe . . . . 0.013
7. Alignment. Alignment should be as straight as possible without undue bends and angle points. Where dictated by physical conditions, curved alignment is permissible as long as there is no reduction in the quality and soundness of joints. The minimum radius of curvature shall be 500 feet.
8. Cover. Except for culverts, outside the hinge point, the minimum cover shall be two (2) feet, measured from the top of the pipe to the roadway or ground surface. Cast-in-place concrete pipes shall have a minimum cover of two and one-half (2.5) feet except under roadways where three (3) feet is required. Where less than minimum cover is necessary the concrete cradle shown in the improvement standards shall be used.
9. Pipe Strength. The class of conduit recommended should be adequate for most conditions. Unusual situations may dictate selection of a higher strength conduit.
10. Location. The location of storm drains relative to roadway centerline shall be in accordance with the improvement standards. Care should be taken that storm drains and other underground facilities do not conflict with each other. Location and elevation of existing and proposed sanitary sewer laterals shall be a primary consideration in the design of the storm drainage facility.
E. Drop Inlets.
1. Types. The standard S-7 drop inlet as set forth in the improvement standards shall be used with pipes up to 30 inches in diameter. A modified S-7 drop inlet or a manhole will be used for pipe larger than 30 inches. Special situation drop inlets are shown in Standards S-7A and S-26.
2. Laterals. Laterals shall have a minimum slope 1%.
3. Location. Drop inlets shall be installed at all gutter low points and at locations such that the flooding limitations of subsection C above are met. They should not be spaced further than 500 feet apart.
F. Manholes.
1. Type. The type of manhole to be utilized shall be as set forth in the improvement standards.
2. Location. Manholes shall be placed:
a. Where two or more storm drain pipes join;
b. Where the conduit changes in size;
c. At angle points;
d. At points where a change of slope in the conduit occurs;
e. At changes in type of pipe.
3. Spacing. The maximum manhole spacing shall be 1,200 feet for pipe diameters of 48 inches or more. Spacing may vary from 350 to 700 feet for diameters less than 48 inches to 33 inches. Maximum spacing shall be 350 feet for conduit 30 inches or smaller.
4. Access Shaft. The access shaft shall be centered over the axis of the drain for conduits less than 42 inches in diameter. The shaft shall be offset and made tangent to one side of the pipe when the drain diameter exceeds 42 inches.
5. Special Structures. Special structures may be required for larger diameter pipes and shall be designed on an individual basis.
6. Grade. The crowns of all conduits intersecting at a manhole shall generally match. A minimum fall of 0.10 foot across the manhole shall be provided except in cases where the conduit is continuous through the manhole.
G. End Structures.
1. General. Headwalls and other end structures shall be installed to increase hydraulic efficiency, prevent erosion adjacent to the conduit and provide a counterweight to prevent flotation.
2. Entrances. When a drop inlet is not installed, flared end sections should be used. Headwalls may be used where dictated by physical conditions. Both installations shall conform to the state standard plans.
3. Exits. Where exists are installed, headwalls or flared end sections should be used for culverts. Where drainage systems discharge into a channel, standard headwalls shall be installed in accordance with the improvement standards.
An approved energy dissipater shall be installed at outlets where velocities are erosive.
H. Open Channels. The director may approve the use of open channels on an individual basis.
The finished channel shall have maintenance free bottom and sides. Minimum bottom width shall be three feet. Side slopes shall be no steeper than1-1/2:1.
All open channels shall be located in dedicated easements. An access road 12 feet wide shall be provided adjacent to the channel.
I. Bank Protection. Bank protection such as slope paving, sacked riprap, and facing rock may be required to protect drainage facilities, property or structures. The need and nature of bank protection will be determined by the director on an individual basis.
J. Temporary Leach Field Type Storm Drainage System. In accordance with the provisions of the “Nitrate Action Plan - Greater Chico Urban Area - Butte County,” adopted by city council Resolution No. 141 84-85 on March 19, 1985 as subsequently amended, temporary leach field type storm drainage systems may be installed for temporary use in cases where the public works director determines that storm water cannot be conveyed to the city’s storm drainage system or drainage channel because facilities are not available. The following criteria shall apply to design of such systems:
1. Percolation tests shall be conducted in accordance with environmental health department procedures. Tests shall be taken at the proposed depth of the drainage trench(es) at such locations as required by the public works director to verify the drainage capacity of the soil. Percolation rate shall be converted from minutes/inch to cubic feet per second/square foot.
2. The trench(es) shall be designed to contain a one-in-ten year frequency storm.
3. The bottom of the trench(es) shall be at least ten feet above the high water table and there shall be at least ten feet of soil capable of percolation below the bottom of the trench(es).
4. The rational formula, Q=CIA, shall be used to determine inflow into trench(es).
5. One-third of the trench(es) volume as void area shall be used in computing amount of storm water storage available in trench(es). Rock size in trench(es) shall be from one-half inch to four inches in size.
6. Fifty percent of the trench(es) bottom area and one-half of the depth of the trench(es) side walls and end walls shall be used in determining the area available for percolation out of the trench(es).
7. Where more than one trench is utilized, there shall be a minimum separation of four (4) feet between trench walls.
8. Limitation on Use of Infiltration Best Management Practices (BMPs). Three factors significantly influence the potential for storm water to contaminate ground water. They are: (i) pollutant mobility, (ii) pollutant abundance in storm water, and (iii) soluble fraction of pollutant. In addition, the distance of the groundwater table from the infiltration BMP may also be a factor determining the risk of contamination. A water table distance separation of ten feet in depth in California presumptively poses negligible risk for storm water not associated with industrial activity or high vehicular traffic. Site specific conditions must be evaluated when determining the most appropriate BMP. Additionally, monitoring and maintenance must be provided to ensure groundwater is protected and that the infiltration BMP is not rendered ineffective by overload. This is especially important for infiltration BMPs in areas of industrial activity or areas subject to high vehicular traffic (25,000 or greater average daily traffic (ADT) on a main roadway or 15,000 or more ADT on any intersecting roadway). In some cases pretreatment may be necessary.
K. Post-Construction Structural or Treatment Control Best Management Practices. Post- construction treatment control Best Management Practices (BMPs) shall incorporate, at a minimum, either a volumetric or flow based treatment control design standard, or both, as identified below to mitigate (infiltrate, filter or treat) storm water runoff:
1. Volumetric Treatment Control BMPs
a. The maximized capture storm water volume for the tributary area, on the basis of historical rainfall records, determined using the formula and volume capture coefficients in Urban Runoff Quality Management, WEF Manual of Practice No. 23/ASCE Manual of Practice No. 87 (1998) pages 175-178 (approximately the 85th percentile 24-hour storm runoff event); or
b. The volume of annual runoff to achieve 80 percent or more capture, determined in accordance with the methodology in Section 5 of the CASQA Storm Water Best Management Practice Handbook, New Development and Redevelopment (2003), using local rainfall data; or
2. Flow Based Treatment Control BMPs:
a. The flow of runoff produced from a rain event equal to at least two times the 85th percentile hourly rainfall intensity as determined from local rainfall records; or
b. The flow of runoff produced from a rain event equal to at least 0.2 inches per hour intensity.
(Res. No. 9 77-78 (part), Res. No. 57 82-83 §5, Res. No. 201 84-85 §1, Res. No. 59 90-91 §§8-10, Res. No. 11 95-96 §1, Res. No. 113-07, Res. No. 65-08, Ord. 2468 §6)
A. Generally. The subdivider shall provide a sanitary sewer system in accordance with the following criteria:
1. The system shall be of a size not less than that which is specified by the sanitary sewer master plan on file with the public works director.
2. The system shall have adequate capacity to serve the subdivision and the full service area tributary thereto in accordance with the city design standards. The tributary area shall be determined by the public works director.
3. When required, the subdivider shall provide a pumping plant to convey the effluent to an existing system.
The director will determine the point of connection to the existing sewer system. The subdivider’s engineer shall prepare a design analysis of the proposed sanitary sewer system in accordance with the sanitary sewer master plan on file with the public works director. When staged construction is proposed, the analysis shall thoroughly cover the design of the entire system.
B. Design Flow. Recommended design criteria for the determination of the sanitary sewer design flow for residential and commercial development are given in Table 5.
The director will determine on all individual basis if industrial waste will be accepted into the city system or if other provision for its on-site disposal will be made.
C. Conduit Design.
1. Type. Sewer conduits shall be extra-strength vitrified clay pipe conforming to ASTM Designation C 200, with plastisol, or equal, compression joints, or polyvinyl chloride (PVC) sewer pipe with a maximum DR of 35, conforming to ASTM Designations D 2784 and D 3034, with flexible elastomeric seals conforming to ASTM Designation D 3212.
In new sewer line construction, wyes to tees for house service connections shall be complete fittings. Saddle type connections will not be permitted.
2. Size. The minimum sanitary sewer size shall be eight (8) inches in diameter except that six (6) inch pipe may be used in the last run in residential areas on cul- de-sacs and in locations where no future extensions of the main are intended.
No sewer pipe shall have a diameter less than that of the pipe immediately upstream from it.
3. Slope. Slope will be controlled by physical conditions and velocity criteria. Abrupt changes in slope are undesirable and should be avoided wherever possible.
4. Velocity. The minimum velocity shall be 1.8 fps when the pipe is flowing full and/or half-full.
5. Head and Head Losses. Sanitary sewers shall be designed to pass the design flow with a free water surface. Proper consideration shall be given to minor head losses.
6. Alignment. Alignment will be straight between manholes with no bends except that curved alignment with a minimum radius of 500 feet may be used in special cases.
7. Location. The location of sanitary sewers relative to roadway centerline shall be in accordance with the improvement standards. Care should be taken that sanitary sewers and other underground facilities do not conflict with each other.
8. Depth. Minimum sewer depth shall be four and one-half (4.5) feet from flowline to finish grade. For unimproved streets where street grades have not been set, the minimum depth shall be five (5) feet from the flowline to existing grade.
D. Manholes.
1. Type. The type of manholes to be utilized shall be as set forth in the improvement standards.
2. Location. Manholes shall be placed:
a. Where two or more sewer mains join;
b. Where the conduit changes in size;
c. At angle points;
d. At points where a change of slope in the conduit occurs.
3. Spacing. Manholes shall be spaced no farther than 350 feet apart.
4. Grade. The crowns of all conduits intersecting at a manhole shall match.
E. Flushing Holes. Flushing holes shall be of the type shown in the improvement standards and shall be placed in accordance with the improvement standards. They shall not be used except in cul-de-sacs or at temporary ends of lines if the end of line does not occur at a manhole. Flushing holes shall be placed no more than 150 feet from a manhole.
F. Laterals.
1. Size. Minimum lateral size for single-family dwellings shall be four (4) inches in diameter. All others will require special design, and design calculations shall be submitted for approval.
2. Slope. Laterals shall have a minimum slope of two (2) percent.
3. Location. Laterals shall be provided for every lot and shall generally be centered on each lot. They shall be at right angles or radial to the sanitary sewer main.
Laterals shall be installed to a point at least five (5) feet into the property prior to other utility installation, pressure testing and subsequent connection to the effluent source.
4. Depth. Laterals shall have a three (3) foot minimum cover at the back of the sidewalk. Where the sewer main is ten (10) feet or greater in depth, deep sewer risers shall be installed.
G. Temporary Pumping Plants. The subdivider’s engineer shall design any needed pumping plants subject to the approval of the director. Each design will be considered on an individual basis.
(Res. No. 9 77-78 (part), Res. No. 87 86-87 §1, Res. No. 86 87-88, Res. No. 113-07, Res. No. 19-13)
A. Size and Type. The size and type of water main pipe shall be determined by California Water Service Company. The sizing shall be based upon the company’s distribution needs and fire flow requirements determined by the city fire department. The type of pipe will be determined by the California Water Service Company.
B. Installation. Installation of water main and services shall be the responsibility of the subdivider. Trench backfill and surfacing shall be in accordance with the city of Chico improvement standards.
C. Certification. Prior to filing the final map, the subdivider shall provide the city with the certification from California Water Service Company. This certification shall state that the company will provide water service to the subdivision and that the subdivider has met all of the company’s conditions necessary to provide water service.
(Res. No. 9 77-78 (part))
A. Installation; Location; Number. Installation of fire hydrants shall be the responsibility of the subdivider.
The number and location of fire hydrants connected to a water supply capable of delivering the required fire flow shall be provided on the public right-of-way and/or on the site to be protected as determined by the fire chief. Standard hydrant spacing shall be at 300-foot intervals in all areas except areas containing only single-story single-family or duplex dwellings, in which case standard hydrant spacing shall be at 500-foot intervals.
When the fire chief determines that it would not be adverse to the city’s fire protection capabilities, the fire chief shall have the authority to make minor modifications to the hydrant placement distances set forth above. In no case shall fire hydrants be spaced closer than 300-foot intervals.
B. Hydrant Type. Approved fire hydrant models are the Long Beach Iron Works Model 614 and 615 or Clow Model 950 or 960. Other hydrant models may be utilized upon approval of the fire chief.
C. Method of Installation. The subdivider shall make all arrangements for the installation and inspection of all fire hydrants with the California Water Service Company.
(Res. No. 9 77-78 (part), Res. No. 149 78-79 §1, Res. No. 196 80-81 §1, Res. No. 59 90-91 §11, Res. No. 02 03-04)
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