Contra Costa County Municipal Code Ch. 914-2 Minimum 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 subdivision, 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 convey 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).

(a) All surface waters flowing from the subdivision in any form or manner shall be collected and conveyed without diversion or damage to any 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 convey 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 department:

(1) 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

(2) A copy of a duly recorded offer of dedication from the adjacent property owners, in a form and content 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.

(3) 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 914-14.

(e) The subdivider shall deposit with the public works department 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 watercourse 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.

(Ord. 89-28, 78-5; Gov. Code, § 66462.5).

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. 89-28, 78-5).

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 average recurrence interval stipulated in Section 914-2.010.

(Ords. 89-28.78-5).

(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 fifty-year frequency of average recurrence interval runoff and contain without freeboard a one-hundred-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 adequate capacity to contain with sufficient freeboard a twenty-five-year frequency of average recurrence interval 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 ten-year frequency of average recurrence interval runoff.

(b) As used in this division, the terms "storm drainage facility" 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).

The county may require that a developer install storm drain improvements for the benefit of the development that may contain supplemental size, capacity, number, or length for the benefit of property not within the development and that such improvements shall be dedicated to the public. In the event of the installation of such improvements, the county shall enter into an agreement with the developer to reimburse the developer for that portion of the cost of such improvements equal to the difference between the amount it would have cost the developer to install such improvements to serve the development only and the actual cost of such improvements. Nothing set forth in this section shall prohibit the county from denying a development where reimbursement funds are unavailable and the developer refuses to construct the improvements necessary to mitigate impacts of the proposed development at the developer's cost.

(a) The county may utilize any of the following methods to pay the cost of administration and reimbursement:

(1) Collect from other persons, including public agencies, using such improvements for the benefit of real property not within the development, a reasonable charge for such use;

(2) Contribute to the developer that part of the cost of the improvements that is attributable to the benefit of real property outside development and levy a charge upon the real property benefited to reimburse itself for such cost paid to the developer;

(3) Establish and maintain local benefit areas for the levy and collection of such charge or costs from the property benefitted;

(4) Condition as part of the entitlement process property outside the development to pay their proportionate share of costs of such facilities attributed to their benefit.

(b) This section will not apply to storm drain facilities as identified on adopted Contra Costa County, flood control and water conservation district drainage area maps and flood control zone maps and plans that qualify for drainage area fees, credits, or reimbursements.

(Ord. No. 2024-23, § III(Exh. A), 12-3-24; Ord. 97-44; Gov. Code § 66485 and § 66486)