Chapter 10 — ROAD STANDARDS, ROAD DESIGN STANDARDS

The following standards for the design of roads represent the minimum values or the lowest acceptable limit in design of roads. These standards apply to both public and private construction. In cases where California State Laws, Nevada County Codes, resolutions or ordinances or project conditions of approval provide for more stringent standards than those shown herein, the more restrictive standard shall prevail.

(Ord. 2488. (01/12/2021); Ord. 2531. (10/24/2023))

Roadways within Nevada County are designated by a functional classification system. Minimum road design standards are based upon the classification of the road or roads being constructed or improved. Roads functionally classified as minor collector or greater may be constructed to a standard of a lessor classified road when it can be demonstrated to the Director's satisfaction that the minimum level of service (LOS) criteria of the Nevada County General Plan can be met for the street or road in question at buildout of the General Plan. Routine repair, maintenance, and safety enhancement projects are exempted from strict compliance with these standards.

A.

General Plan Classifications. Interim Classification Map, Until final adoption by the Nevada County Board of Supervisors of the revised Nevada County General Plan, the 1992 Functional Classification Map approved by the Federal Highway Administration (FHWA) on September 8, 1993, shall be the map referred to by the following paragraph. Upon final adoption of the Nevada County General Plan that map will be superseded by the Nevada County General Plan Land Use and Circulation Maps. The FHWA maps served as a basis for the recommended classification of County roads in the Nevada County General Plan. Upon final adoption of the General Plan, requests will be submitted to amend the FHWA Maps to be consistent will the Nevada County General Plan.

Regionally significant roads are classified by the General Plan or addendum to the General Plan. These roads are identified on General Plan or specific plan maps or other descriptions. Some of these roads may be maintained by the State or by the cities.

Interstate Highways and Freeways. Limited access highways (e.g., Interstate 80 and the Golden Center Freeway).

Principal Arterials. Roadways carrying some regional traffic and connecting the major population centers within the County (e.g., State Route 49 south of Grass Valley and State Route 20 west of Grass Valley).

Minor Arterials. Roadways providing primary access from freeways and principal arterials to major origins and destinations (e.g., Nevada City Highway, Brunswick Road and State Route 174).

Collectors (Major and Minor). Streets connecting arterials to local roads. Collectors are broken down into the subcategories of Major and Minor in the rural area of the County (e.g., [Urban] Collector, Sutton Way; [Rural] Major Collector, Alta Sierra Drive; [Rural] Minor Collector, Norlene Drive).

Local Road Classifications. The classification of roads not classified as minor collector and above by the General Plan Circulation Map is local road. These roads function primarily to provide access to individual properties. The standard to which these roads are to be constructed is determined by the type and intensity of the adjacent land uses. The class of local road will be determined by the estimated future Average Daily Traffic (ADT). The future ADT shall be computed using the sum of existing traffic, plus any additional traffic generated from land uses allowed under the County's current General Plan and the Title 12, Zoning, of this Code. For the purpose of implementing the General Plan, local roads can be broken into the following subcategories:

a.

Minor Collector Equivalent (Local Class 3) Road: Serves a buildout volume in excess of two thousand (2,000) Average Daily Trips (A.D.T.) and is constructed to the same standard as those roads classified as minor collector on the General Plan Circulation Plan.

b.

Local Class 2: Serves a buildout volume of four hundred one (401) to two thousand (2,000) Average Daily Trips (A.D.T.).

c.

Local Class 1: Serves a buildout volume of one hundred one (101) to four hundred (400) A.D.T.

d.

Fire Standard Access Road: Is the minimum standard for access to a driveway for new construction and serves a maximum of one hundred (100) A.D.T.

B.

Future Traffic Generation. Future traffic generation from allowed land uses will be based on the trip generation factors in the latest edition of the Institute of Transportation Engineers (ITE) Trip Generation Manual unless specific local studies have been conducted and accepted for conditions unique to Nevada County. In the case of uses not specifically listed in the ITE Trip Generation Manual or for which local studies have not been conducted, the most similar use will be used.

The Chart on the following page summarizes the above Classifications.

TABLE I NEVADA COUNTY ROAD CLASSIFICATION SYSTEM

(Ord. 2488. (01/12/2021); Ord. 2531. (10/24/2023))

When a subdivider is required to provide as an improvement a road functionally classified as a minor collector or greater within or adjacent to their development, the right-of-way shall conform to the width and alignment standards contained herein for functionally classified roads. Oversizing of improvements may be required due to the eventual capacity needs of cumulative growth beyond the infrastructure needs generated by an individual project. Such oversized improvement may be subject to a reimbursement agreement pursuant to Sections 16.10.020 and 16.10.050 of this Chapter. If the project needed to

accommodate cumulative growth is contained within the list of projects upon which development fees are based, credit towards an individual project's development fees may be given in lieu of entering into a reimbursement agreement for the oversized improvement. All construction, including cut and fill slopes, shall be contained within the right-of-way offered for dedication.

A.

Offsite Access. The subdivider shall provide proof of adequate offsite right-of-way. Adequate offsite right- of-way is defined as the legal right of the developer and his assignees to use of a road that is of sufficient width to contain the entire road prism (including cut and fill slopes) which is required under this Chapter and which provides access to a County road or State highway. When the parcels being created are less than three (3) acres in size, the subdivider shall improve offsite County roads to a minimum of the local class road standard appropriate to the project based on the future ADT. In the case that an existing offsite County maintained access road is not within the Nevada County Department of Public Works Five Year Road Capital Improvement Program for upgrading to be adequate in capacity to accommodate the additional traffic to be generated by a specific project, the developer shall be responsible for upgrading the offsite County road to the standard appropriate to the existing traffic plus the traffic calculated to be produced by the project.

B.

Existing County Roads. The subdivider shall surface existing onsite County roads in accordance with the standards based on the traffic that will be generated by the subdivision. The minimum road prism, including cut and fill slopes, to be constructed shall be that standard appropriate to accommodate cumulative growth and shall be subject to the oversizing provisions as discussed above under "Construction of Major Roads."

C.

Street Extensions. Streets which are to be extended in the future are not required to be constructed providing they do not exceed one (1) lot in depth and provided all lots adjacent to such streets have adequate frontage on and access to another street. Right-of-way and slope easements sufficient for construction shall be provided.

(Ord. 2239. (05/29/2007); Ord. 2488. (01/12/2021); Ord. 2531. (10/24/2023))

A.

Design Widths and Speeds. The minimum design widths, speeds and other major design criteria for road construction are as follows in the chart on the following page. Further details are provided in the County's Standard Drawings which supplement this Chapter.

TABLE II NEVADA COUNTY STANDARD SPECIFICATION SUMMARY CHART

Note 1: All structural sections for this classification based on future year traffic and estimated percentage of that traffic which will be heavy vehicle.

Note 2: Surface capable of supporting a seventy-five thousand (75,000) pounds vehicle with a minimum six (6")-inch A.B. compacted to ninety-five percent (95%) with subgrade compacted to ninety-five percent (95%).

Note 3: Driveway standard specifications are contained in Title 4 of the Nevada County Code, Fire Safety Regulations.

Note 4: Intersection channelization may increase the minimum right-of-way at spot locations.

Note 5: If approved by the engineer, all grades over ten percent (10%) will require minimum three (3")-inch A.C. surface (Section 16.10.040[C]).

Note 6: All roads shall be constructed to provide a minimum of two (2) ten (10')-foot traffic lanes, not including shoulder and striping.

The Nevada County Department of Public Works Standard Drawings, available from the Nevada County Department of Public Works, illustrate and clarify the standard specifications contained within this Chapter, as well as the Driveway specifications.

B.

Horizontal Alignment. Changes in horizontal alignment of roads shall be made with horizontal circular curves with the edges of the pavement parallel to and equidistant from the centerline. Design of the horizontal alignment of roads shall be in accordance with the standards outlined in the California Department of Transportation "Highway Design Manual" in accordance with the appropriate design speed. Unless otherwise approved by the engineer, the centerline of the road improvement shall coincide with the right-of-way centerline or other previously approved alignment.

C.

Vertical Alignment. Grade changes in the vertical alignment greater than two percent (2%) shall be designed with parabolic vertical curves. The maximum grade, unless otherwise specified or approved by the engineer, is ten percent (10%) below three thousand five hundred (3,500')-foot elevation and eight percent (8%) above three thousand five hundred (3,500')-foot elevation. The maximum grade without an Exception shall be sixteen percent (16%). The minimum grade for all classes of roads is one-half percent (0.5%). The design of the vertical alignment of roads shall be in accordance with the standards outlined in the California Department of Transportation "Highway Design Manual" in accordance with the appropriate design speed.

The minimum vertical curve data to be complete and shown on the improvement plans shall identify the point of intersection elevation, the tangent gradients, the middle ordinate and the length of curve.

The minimum length of a vertical curve shall be one hundred (100') feet.

D.

Ross Slope Design. The standard cross slope for all roads shall be two percent (2%), sloping both directions from the "crown" or highpoint at the centerline towards road edge. Any deviation from this standard requires prior approval from the engineer.

Superelevated cross sections in horizontal curves shall have a maximum rate of superelevation of six percent (6%) for roads below three thousand five hundred (3,500) elevation. For roads at elevation three thousand five hundred (3,500) or above, the maximum rate of superelevation shall be four percent (4%).

E.

Intersection Design. Intersecting roads shall not exceed six percent (6%) grade for a minimum of thirty (30') feet from the edge of the traveled way of the intersecting road.

All roads shall intersect as nearly as possible at right angles, but in no case shall the angle of intersection be less than sixty (60) degrees.

Roads intersecting any road from opposite sides shall have their centerlines directly opposite, or the offset between intersections shall be a minimum of one hundred fifty (150') feet.

Minimum sight distances for intersections shall be designed to meet all standards as shown in the Nevada County Standard Drawings, required sight distance at intersection/driveways.

F.

Curve Widening. No road or roadway structure shall have an inside radius of less than fifty (50') feet. In cases where the centerline radius of a road is less than or equal to two hundred (200') feet, the inside edge of pavement shall be widened by four (4') feet. In cases where the centerline radius is one hundred (100') to two hundred (200') feet, the inside edge of pavement shall be widened by two (2') feet.

G.

Additional Rights-Of-Way. The advisory agency may require additional rights-of-way to accommodate traffic or parking on business or major traffic streets. The advisory agency may also require right-of-way for non-vehicular traffic (i.e., bikeway, equestrian path, foot path, if the right-of-way is shown on an adopted master plan or specific plan).

H.

Slope Easements. Slope easements shall be provided wherever they are needed to contain the cut or fill slopes. The slope easement line shall be set at the toe of the fill or top of the cut plus ten (10') feet.

I.

Cul-De-Sac. Roads that dead end or transition to a driveway or non-standard road shall be terminated with a bulb-shaped cul-de-sac at the point where the road ends or transitions as shown in standard drawings. Cul-de-sacs shall have a minimum forty (40')-foot radius surfaced bulb, measured from the center of the bulb to the edge of the surfacing if parking is not allowed on the road. If parking is allowed on the road, a minimum fifty (50')-foot radius surfaced bulb shall be provided. Said surfacing shall be the same as required for the terminating road.

Hammerhead turnaround designs may be utilized subject to approval by the engineer for local class roads when unusual topographic or other conditions prevent cul-de-sac construction. If a hammerhead-T is used, the top of the "T" shall be a minimum of sixty (60') feet in length.

The maximum length for a cul-de-sac or other dead-end road, including all dead-end roads accessed from that dead-end road, shall not exceed the following cumulative lengths, regardless of the number of parcels served:

Parcels zoned for less than one (1) acre eight hundred (800') feet.

Parcels zoned for one (1) acre to four and ninety-nine one-hundredths (4.99) acres one thousand three hundred twenty (1,320') feet.

Parcels zoned for five (5) acres to nineteen and ninety-nine one-hundredths (19.99) acres two thousand six hundred forty (2,640') feet.

Parcels zoned for twenty (20) acres or larger five thousand two hundred eighty (5,280') feet.

All lengths shall be measured from the edge of the road surface at the intersection that begins the road to the end of the road surface at its farthest point. Where a dead-end road crosses areas of differing zoned parcel sizes, requiring different length limits, the shortest allowable length shall apply.

For parcels zoned for five (5) acres or larger, turnarounds shall be provided at maximum one thousand three hundred twenty (1,320')-foot intervals.

Each dead-end road, including gated access roads, shall have a turnaround constructed at its terminus.

J.

Utilities Placement.

In no case shall utility poles, light standards, guy wires, etc. be placed closer than six (6') feet to the edge of the traveled way. Manhole covers, grates, valve boxes, etc. shall be set so as not to interfere with snow removal.

New utilities shall be located as follows:

a.

Water: Three (3') feet from edge of pavement on the north or west side of the road;

b.

Sewer: Five (5') feet from the road centerline on the south or east side of the road;

c.

Storm Drains: Five (5') feet from the road centerline on the north or west side of the road;

d.

Joint trenches, telecommunications and other utilities: Either side of the road and at least six (6') feet from the centerline of roadside ditches.

Telecommunication Requirements. The installation of conduit for telecommunication purposes is required for all Capital Improvement Projects, development projects and Encroachment Permit work that includes any of the following:

a.

All new arterial/collector road and bridge construction.

b.

All new subdivision roads where underground utilities are required.

c.

Arterial/collector road reconstruction/widening involving reconstruction of the base and/or subbase on sections of a road spanning: 1) between two (2) road intersections or more; or 2) one thousand (1,000') feet in length or more.

d.

Bridge reconstruction.

e.

Trench work on arterial/collector roads spanning: 1) between two (2) road intersections or more; or 2) one thousand (1,000') feet in length or more.

An exception may be granted in writing by the Director per the following:

a.

Capital Improvement Projects: Separate alternative bid items will be required for all projects where telecommunication conduit is required per the above. If funding is not identified from the County or others upon award of a construction contract or upon commencement of the work by the County, an exception may be granted.

b.

Development project, non-County maintained road and/or Encroachment Permit work: An applicant may request funding from the County for the cost to construct telecommunication conduit if other funding sources are not available, less any costs shared by other utilities. Requests must include the associated project name, associated County permit numbers, an engineer or contractor estimate with a separately identified cost for construction of conduit for telecommunication use, the amount requested and any additional pertinent information. Approval of funding from the County will require Board of Supervisor approval of a funding agreement. In addition, an applicant may request to install conduit on other roads (other than arterials and collectors) for County consideration.

c.

Any location where trenching is not advisable per a stamped and signed report from a licensed geologist, geotechnical engineer or civil engineer.

Conduit for telecommunication purposes shall be a minimum of four (4")-inch HDPE constructed per County trench backfill requirements with pull boxes every two hundred fifty (250') feet. Telecommunication

conduit must be constructed in road right-of-way or in Public Utility Easements or equivalent and may be constructed in joint trenches with other dry utilities. Completed telecommunication conduits must be granted to a telecommunication company or the County of Nevada.

K.

One-Way Roads. One-way roads may be permitted subject to the approval of the engineer. In no case shall one-way roads serve more than ten (10) dwelling units or exceed two thousand six hundred forty (2,640') feet in length. Standard one-way road structural sections are as shown on the Nevada County Standard Specifications Summary Chart. The surfacing requirements for one-way roads shall be the same as for the overall project of which they are a part. One-way roads shall serve only one (1) direction of traffic and shall be signed appropriately and to the satisfaction of the entity responsible for fire protection. One-way roads shall connect on both ends to a two-way road.

L.

Minimum Vertical Clearance. The minimum vertical clearance over all roadways shall be fifteen (15') feet.

M.

Gates On Access Roads.

Gate entrances shall be at least two (2') feet wider than the width of the traffic lanes serving the gate and shall have a minimum gate opening of fourteen (14') feet.

All gates providing access from a road to a driveway or another road shall be located at least thirty (30') feet away from the primary road right-of-way or easement and shall open to allow a vehicle to stop without obstructing traffic on that primary road.

All gates installed on emergency access roads after May 14, 2010 shall be subject to the following provisions:

a.

At no time shall a gate on an emergency access road be locked.

b.

The following standard signage shall be required on all gates on emergency access roads: "Emergency Access Only. This Gate Shall Remain Unlocked."

c.

Pursuant to the enforcement powers established by the Nevada County Code Sections 16.15.030 and 16.15.040, the County, or an agent of the County, reserves the right to remove locks from gates or to remove other encumbrances, including but not limited to boulders, ditches, and berms, that inhibit the use of an emergency access road for its intended purpose.

All gates installed prior to May 14, 2010, shall be subject to the legal requirements, standards and/or conditions that were applicable at the time of original approval and installation.

Security gates shall not be installed without approval of the Fire Marshal's Office of the fire authority having jurisdiction. Where security gates are installed, they shall have an approved means of emergency operation. The security gates and the emergency operation shall be maintained operational at all times.

(Ord. 2239. (05/29/2007); Ord. 2474. (01/14/2020); Ord. 2488. (01/12/2021); Ord. 2531. (10/24/2023))

A.

Minimum Structural Section Standards According To Road Class And Parcel Size. Streets within the parcel(s) being developed and offsite non-county maintained access to the parcel(s) are to be brought/constructed to the minimum structural section condition indicated in the following table for the classes of streets within the parcel and the offsite access street and the parcel size being created. Higher standards are required if dictated by the projected traffic from the project.

TABLE III MINIMUM SURFACING STANDARDS BY PARCEL SIZE AND FUNCTIONAL CLASSIFICATION

Note 1: Minimum requirements. Actual structural section design to be based on "R" value and "T.I."

Note 2: Six (6") inches A.B. = 6″ A.B. at ninety-five percent (95%) compaction over subgrade compacted to ninety-five percent (95%). If grade exceeds ten percent (10%), surface shall be three (3")-inch A.C. over six (6")-inch A.B. Higher Standards are required if dictated by projected traffic from project.

B.

Structural Section Design. The structural section design shall be based on the R-value of the underlying material, with the minimum structural sections as shown above and on the Standard Drawings. The location of R-value tests within the project area shall be selected so as to provide representative samples for the entire project area. Additional testing may be required in specific soil areas as directed by the engineer.

C.

Aggregate Base (AB) or Base. Class 2 Aggregate Base is aggregate base in conformance with the provisions of Section 26, "Aggregate Bases" of the CALTRANS Standard Specifications.

D.

Double Seal. Double seal coat is seal coat in conformance with the provisions of Section 37, "Bituminous Seals" of the CALTRANS Standard Specifications.

E.

Asphalt Concrete (AC) Paving or Pavement. Type B asphalt concrete is asphalt concrete in conformance with the provisions of Section 39, "Asphalt Concrete" of the CALTRANS Standard Specifications.

(Ord. 2474. (01/14/2020); Ord. 2488. (01/12/2021); Ord. 2531. (10/24/2023))

Sign type and location shall conform to the following:

A.

Street Signs. Street signs shall be of the type and size as shown in the Nevada County Standard Drawings. A street sign installation with four (4) sign plates on each post is required at each intersection. The location of street sign installations shall be shown on the improvement plans.

B.

Traffic Signs. Stop signs, speed limit signs and other traffic control signs shall be of the size and type and shall be installed in locations that are in conformance with the State of California, Department of Transportation Traffic Manual and as required and approved by the engineer.

(Ord. 2488. (01/12/2021); Ord. 2531. (10/24/2023))

A.

Curb, gutter and/or sidewalk shall be installed adjacent to all road improvements where required by ordinance, resolution or as a Condition of Approval for the project. Type E rolled curb and gutter and the sidewalk adjacent to the curb and gutter shall be placed upon a layer of Class 2 aggregate base compacted to ninety-five percent (95%) relative compaction. The depth of the aggregate shall be thick enough so that when combined with the concrete above the resulting structural section is equivalent to that of the adjoining roadway. In no case shall the depth of Class 2 aggregate be less than two (2") inches.

B.

Type A2-6 curb and gutter shall be placed upon a layer of Class 2 aggregate base as described for Type E rolled curb and gutter except that the sidewalk adjacent to Type A2-6 curb and gutter need not be placed upon aggregate base, provided that the subgrade is compacted to ninety-five percent (95%) relative compaction. All curb, gutter and sidewalk shall be constructed in accordance with the latest edition of the State of California, Department of Transportation Standard Plans and Section 73, "Concrete Curbs and Sidewalks" of the Standard Specifications.

C.

In areas above the three thousand five hundred (3,500')-foot elevation, Type E rolled curb and gutter shall be constructed (see CALTRANS Standard Plans).

D.

The minimum width for all sidewalks shall be four (4') feet except as otherwise specified or required.

E.

Sidewalks shall be six (6') feet wide at bus turnouts and at signalized intersections. Where utility poles or other obstructions are situated within street-side sidewalks, a minimum of four (4') feet of clear uninterrupted sidewalk area shall be provided. Where it is necessary to widen the sidewalk beyond the standard width to obtain the four (4')-foot clearance, the widened area shall extend a minimum of five (5') feet beyond each side of the obstruction and a ten (10) foot taper on each side of the widening shall be required.

F.

All construction shall comply with the Americans With Disabilities Act of 1990 (42 U.S.C.S. §§ 12101, et seq.).

(Ord. 2488. (01/12/2021); Ord. 2531. (10/24/2023))

All bikeways shall be constructed in locations designated by and designed in conformance with the Nevada County Bicycle Master Plan and the CALTRANS Highway Design Manual, Chapter 1000, "Bikeway Planning and Design."

(Ord. 2488. (01/12/2021); Ord. 2531. (10/24/2023))

Snow stakes shall be provided and placed by the Department where applicable. The Developer shall be responsible for payment to the Department for this service on a one-time-only basis.

(Ord. 2488. (01/12/2021); Ord. 2531. (10/24/2023))

Snow storage easements shall be provided in subdivisions above 3,500 feet elevation and shall be ten (10') feet wide on both sides of the road right-of-way.

(Ord. 2488. (01/12/2021); Ord. 2531. (10/24/2023))

If the roads constructed within a subdivision are to remain private, then a maintenance entity shall be formed to insure continued maintenance on the road system. Maintenance of the road system shall include maintenance of the fuel modification zones and minimum vertical clearances. The entity shall be formed in accordance with the Standard Maintenance Agreement on file in the Department of Public Works. The subdivider may be required to annex to an adjacent existing maintenance entity.

(Ord. 2488. (01/12/2021); Ord. 2239. (05/29/2007); Ord. 2531. (10/24/2023))

Modification of the required standard, except as provided within this Chapter, for the construction of specific roads shall follow the petition for exception process as specified in Section governing Subdivisions of this Code. Otherwise, the Advisory Agency, in the case of petitions for exceptions from the road standards, shall be required to make findings of fact in support of the following in addition to those findings of fact specified in Section governing Subdivisions.

That an exception to any fire safe standard, including those standards adopted by Title 4, governing Fire Safety Regulations of this Code and the Chapter governing Fire Standard Access Road improvements, will provide the same practical effect of fire protection and is supported by the entity responsible for assuring compliance with Cal. Code Regs. Tit. 14, Natural Resources Division 1.5, Department of Forestry and Fire Protection Chapter 7, Subchapter 2, Articles 1—5.

The same practical effect can be met in some cases by incremental improvements of offsite access roads proportional to the intensity of development proposed.

It is intended that every effort be made to grant a petition for exception that includes feasible road improvement requirements for tentative parcel maps for living persons, or the testamentary disposition of deceased persons, who owned their property prior to March 4, 1972. The Board finds that such property owners have contributed significantly to the public trust through open space conservation by avoiding development of their property in prior years.

All requests for design exceptions shall be reviewed and approved by the County Engineer. In the case of requests for design exceptions for privately funded improvement projects, the Advisory Agency shall take action on the recommendation of the County Engineer and the findings for or against the exception shall be noted in the finding of facts either approving or denying the petition. All Petitions for Exceptions shall contain, at a minimum, the information requested on a Design Exception Information Form to be provided by the Department.

(Ord. 2161. (10/05/2004); Ord. 2474. (01/14/2020); Ord. 2488. (01/12/2021); Ord. 2531. (10/24/2023))