As a part of its operating system, IID maintains an extensive gravity flow drainage system. The lateral drain system is laid out to provide a drainage outlet for each governmental subdivision of approximately 160 acres and, as such, the drains usually parallel the canals.

The district is obligated to provide its drains at sufficient depth - generally 6 to 10 feet deep - to accept tile drain discharge. Where the drain cannot be maintained at sufficient depth, a sump and pump are provided and maintained by the district. These drains are used to collect excess surface flow (tailwater) from agricultural fields, subsurface tile discharges and operational discharge from canals and laterals.

There are over 1,450 miles of surface drains that can be divided into three main areas: Alamo River System, New River System and drains that flow directly into the Salton Sea. Approximately 430 control structures are installed along the drainage system.

Drainage Water Quality
The State of California’s Water Quality Assessment document, adopted by the California Regional Water Quality Control Board, Colorado River Basin – Region 7 (Regional Board) in January 1994, classified the Alamo River, New River, and Salton Sea as water bodies impaired by agricultural nonpoint sources.

In June 1994, IID developed a Drain Water Quality Improvement Plan in response to the Regional Board’s demand for action regarding these water quality impairments. The DWQIP was in effect until March 1998, at which time the Regional Board requested that these efforts be suspended until Total Maximum Daily Loads could be developed and implemented for these water bodies.

Following the development and implementation of the Alamo River Sedimentation/Siltation TMDL, in September 2003 IID submitted a Revised DWQIP to the Regional Board, as required in the Region 7 Water Quality Control Plan. The Revised DWQIP states that IID will perform monthly water quality monitoring within 14 drains throughout the service area for several constituents of concern and report these results to the Regional Board.

The IID has also performed special studies to determine water quality impacts caused by drain maintenance operations and continues to supply the Regional Board with a list of current owners and tenants of agricultural land on a semi-annual basis.

In January 2015, the Regional Board adopted Order R7-2015-0008, a “Conditional Waiver of Waste Discharge Requirements for Agricultural Wastewater Discharges and Discharges of Wastes from Drain

Operation and Maintenance Activities within the Imperial Valley, Imperial County, California”. The development of this conditional waiver follows the 2012 denial of Palo Verde Irrigation District’s conditional prohibition by the State Water Resources Control Board, which previously had served as the permitting mechanism for agricultural discharges and the TMDL program. That denial signaled a change in the SWRCB’s direction for California farmers and landowners in an attempt to be consistent with the approach used by other regional boards. The conditional waiver is largely a conditional prohibition with an added fee.

Requirements of the conditional waiver essentially have replaced the previous conditional prohibition program, although many of the monitoring and BMP requirements remain unchanged. One substantial change included in the waiver is the addition of a coalition group compliance program for agricultural dischargers to obtain regulatory coverage.

Click here, to contact IID’s water quality section for more information.

IID Drain Water Quality Improvement Plan - revised 5/4/2005 [PDF]
IID/ICFB Coalition Group Compliance Program - Board Presentation- Feb. 17, 2015 [PDF]
DWQIP Report Monitoring Sites [PDF]