Humboldt County officials, resident debate fixes for clogged forebay, corn-stalk runoff

Humboldt County officials on Tuesday heard from a property owner about a forebay intended to trap silt and debris that is no longer functioning as designed and is sending corn residue and other material into a downstream pond.

The property owner, identified in the meeting only as Mark (resident/property owner), said the feature labeled the “4 Bay” alongside Birch Avenue is acting like a rock pile rather than a working forebay and that corn stalks and other debris “float on the top of the water in the forebay, and then go over the rock.” County staff and board members discussed the forebay’s design, maintenance history and possible short- and long-term fixes.

County engineering staff described the constructed forebay as roughly 10 feet deep, about 60 feet wide and 130 feet long. The group said the state paid about 75% of the overall ag-drainage project that included the forebay and an associated pond; the drainage district covered the remaining 25% of construction costs. The meeting record shows the forebay was installed nearly 10 years ago and has accumulated enough settled material that it now traps far less than intended.

The discussion focused on two linked problems: surface runoff of crop residue from fields west and south of the road, and a rock berm at the forebay’s outlet that appears to be preventing the feature from draining through its intended riprap. County staff said a properly functioning forebay typically allows water to trickle through engineered rock and be accessed more easily for periodic cleanout; the current configuration has become plugged with organic debris and fine sediments, staff members said.

Participants reviewed several possible responses, all with trade-offs. Suggestions included installing fencing or hog panels at the road’s west side to intercept residue before it crosses the road, regrading or lowering the rock berm to permit the forebay to drain to a lower level, and replacing the outlet material with a combination of larger and smaller graded rock to create a ‘‘stone weeper’’ arrangement that could be cleaned more easily. Speakers warned, however, that any structure that traps residue will require ongoing maintenance and can itself become an obstruction if material piles up and causes water to back onto upstream property.

A recurring concern at the meeting was who would pay for ongoing maintenance, including potential dredging if the pond behind the forebay fills with sediment. Staff noted the drainage district’s legal assessment authority under state drainage law and said the forebay sits at the outlet of the drainage district. However, they said the specific parcel where the pond sits is not technically inside the district and that question could affect whether the district could be assessed for major maintenance costs.

Board members and staff agreed on a next step: county staff (identified in the record as Bruce and Mike) will speak with the upstream landowner and explore conservation practices and short-term mitigations. The meeting record shows no formal vote on the matter; instead, staff were directed to investigate options and report back.

Speakers emphasized the limits of any technical fix: agricultural practices and wind-driven residue can continue to discharge large volumes of material during heavy rain events, and any on-road interception or structural device will require long-term maintenance and landowner cooperation. The board said it would begin by contacting the adjacent landowner and exploring conservation or fencing options before pursuing structural changes.