Drainage & Erosion

Drainage & Erosion  *  Guidelines  *  Rainfall Intensity

Special Permit Zones Map  *   Drainage Basin Map

DEVELOPERS, CONTRACTORS AND HOMEOWNERS ARE URGED TO INSTALL
EROSION AND SEDIMENT CONTROL MEASURES ON ALL NEWLY
DISTURBED SURFACES PRIOR TO THE ONSET OF WINTER RAINS

After a long, dry summer, the onset of the winter rainy season is rapidly approaching. To help protect the quality of our creeks and streams in Paradise, contractors and homeowners that have disturbed the soil surfaces around their property are urged to install erosion and sediment control devices prior to the onset of the winter rains.

Most commercial building projects and projects with grading permits issued have mandatory erosion and sediment control measures associated with their approved plans. These control measures are designed to minimize the off-site transport of silt and turbidity into the nearby streams. It is the property owner’s responsibility to make sure that all measures are in place and continue to be effective during the winter months.

Smaller projects may not have specific erosion and sediment control requirements. For those projects without specific requirements, property owners are encouraged to discuss their particular situation with their contractor or the Town of Paradise engineering division. The goal of any erosion and sediment control measure is to prevent the contamination of streams, loss of fish habitat and damage to the environment.

Examples of effective erosion control measures included re-seeding slopes with annual grass mixtures followed by placement of straw mulch, hydroseeding slopes, placement of jute matting, erosion control blankets or placement of sod.

Property owners that do not install and maintain the appropriate erosion control measures are subject to fines by both the Town of Paradise and the Regional Water Quality Control Board. The fee for a Town of Paradise inspector to visit a non-compliant site and to write an abatement letter is $120.00 per incident. If the Regional Water Quality Control Board is involved, due to either the size of the site (greater than 1 acre of disturbed area), the nature of the discharge, or owner non-compliance with their Storm Water Pollution Prevention Plan, property owners can face fines of $10,000 per day and up, depending upon the severity of the problem and the amount of discharge.

For more information:
CalTrans Storm Water Information
Regional Water Quality Control Board
EPA Report to Congress

INTERIM DRAINAGE DESIGN GUIDELINES
PREPARED APRIL 2, 1998

The following drainage design criteria have historically been utilized for the design of drainage facilities within the Town of Paradise. This is an attempt to provide designers with a written set of guidelines, prior to adoption of a full set of drainage design criteria by the Planning Commission and Town Council. These are intended to be the minimum acceptable standards, each site must be evaluated individually by the Engineer of Record. All calculations and improvement plans shall be stamped and signed by the Engineer of Record. All facilities shall be designed in accordance with generally acceptable engineering practices, the latest adopted Uniform Building Code (including grading provisions), and the following specific design criteria:

Hydrology

Method - Rational or TR-55.

Design Storm 2 Tables (attached).

Calculations shall include tributary area map(s), area calculations, time of concentration calculations, runoff coefficient calculations and all other pertinent assumptions and calculations.

Acceptable references are the Caltrans Highway Design Manual, latest edition, and Butte County Improvement Standards, 1991 edition, and the Town of Paradise Rainfall Intensities.

Setbacks

All designs shall comply with the Onsite System setbacks listed in Table 3.1, Onsite Wastewater Manual.

Minor Underground Storm Drain Pipes & Structures (24" Diameter and Smaller)

Design to flow 10 year storm, fully developed site, without using available head.

Check design with 100 year storm, if significant damage is possible, upsize facilities.

Major Underground Storm Drain Pipes and Structure (greater than 24" Diameter)

Design to flow 100 year storm, using available head.

Minor Channels (less than 100 acres tributary)

Design for 10 year storm, with ½ foot freeboard.

Check design for 100 year storm, if significant damage is possible, upsize facilities.

Design shall include erosion control measures.

All channels greater than 6% slope shall be lined.

Major Channels (more than 100 acres tributary)

Design for 100 year storm, with 1½ foot freeboard.

Design shall include erosion control measures.

All channels greater than 6% slope shall be lined.

Downstream Impacts

All developments of 5000 square feet of developed area or greater shall be required to provide a drainage impact analysis of surrounding and downstream properties. This impact analysis should include all areas downstream where the project may have a significant impact.

Detention Pond Design:

Design storm inflow - 100 year storm, fully developed site.

Infiltration - rates must be substantiated with percolation test(s) or soil information.

Underground detention/infiltration ponds should incorporate slurry cut-off walls into design to reduce potential for flooding of nearby onsite sanitation disposal systems (see setbacks in Onsite Manual).

Outflow - 10 year storm, undeveloped state, using tc based upon site characteristics. This outflow will be into an acceptable drainage facility. Provide calculations to justify the proposed discharge, and check downstream capacity of all street ditches, gutters, pipes and channels.

Spillway - design spillway to handle 100 year storm, assuming plugged outfall. The spillway discharge shall be lined, shall be into an acceptable drainage way or public street..

Design for 100 year storm, with 1.0 foot of freeboard.

Provide means of maintaining structure (recorded maintenance agreement or other methods as approved by the Town Engineer).

Rainfall Intensity

Rainfall Intensity ( i ) is defined as the intensity of rainfall of a chosen frequency that lasts for a duration equal to the time of concentration. The units for rainfall intensity are (inches per hour).

Rainfall intensity is one of the variables used by licensed engineers to determine the quantity of rainfall in a given drainage area at a certain outfall location using the Rational Method.

Rainfall Intensities for the Town of Paradise are subdivided into two frequencies, a 10 year and 100 year return period. Ten year storms are to be used when the design of such drainage system will result in no loss of property or safety issues in the event of overtopping.

For more information about the Rational Method please visit the following websites:
Federal Highway Administration
OR
Caltrans

For more information about the Town's adopted drainage guidelines, click the link below:
INTERIM DRAINAGE DESIGN GUIDELINES

Click here for a Storm Damage Report form. (Please print and FAX to 877-5057, Attn: Paul Derr)

Back to Public Works

Town of Paradise Home * Town Government * Town Council * Budget & Finance * Economic Development * Planning Commission * Building Permits * Economic Revitalization * Business & Housing * Public Works * What's New * Redevelopment * Police Dept. * Fire Dept. * Homeland Security * Public Meetings * Onsite * Links * Contacts * Feedback * Site Map