PROJ00434

• Contract/PO #: C153337
• Contractor Name: Farmers Extension Ditch & Highland Lake Lateral Company
• Contract Type: Loan
• Water District: 1
• County: Weld
• Bill Number: FSA
• Loan Projects - Doc Type: Feasibility Study

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DRAINAGE

There are nine drainage basins which affect the Highland Lateral and Farmers Ex-

tension Irrigation Ditch (Exhibit No.6). The largest of these basins is appro-

ximately 750 acres in size and the smallest is less than 100 acres. The irrigation

ditch has played an important role with regards to the storm water collection

and routing that has occurred over the years. It has diverted much of the storm

water which; before the ditch was constructed flowed over historical drainage

basins. Diverted storm waters have been carried in the ditch where it has excess

capacity. However, when this storm flow reaches sections of the ditch which does

not have excess capacity it then flows over the embankments. These overflow points

sometimes are in drainage basins which are not native to the drainage basins in

which the storm waters were developed. A greater problem is that the storm flows

increased the amount of erosion and scour in the ditch and carved away at the

embankments so that the ditch lost its compaction and, therefore, its ability

to prevent water from seeping. As this problem continues, the ditch becomes

bigger, more unstable, and harder to maintain.

It is imperative that when any design is done for the rehabilitation of the ditch

that a drainage study be completed to determine the potential affects of storm

water on the ditch as well as the existing agriculture and developments in sur-

rounding areas. The drainage study should include all of the drainage ~basin

areas of the Highland Lateral and Farmers Extension Irrigation Ditch. In this

way, the Soil Conservation Service can accurately design the new ditch with

accurate storm drainage considerations, or no storm waters at all.

In lieu of the recommended drainage study we have designed for drainage with as

much foresight as possible, we feel that no major problems in sizing will occur.

The alternative we have chosen for the project rehabilitation will end up col-

lecting some storm drainage. This drainage shall be discharged from the ditch

through possible storm water outlets shown on Exhibit 6. It is possible that

the ditch will have to have special inlets constructed so that silt and sedi-

mentation are not discharged into it along with the storm waters. We feel that

at least in one area a flume should be built over the concrete lined ditch to

channel the storm waters properly.

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