Water and silt from the Five-Mile Basin during high flows, and how a crew reads and dries the damage.
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Five-Mile Basin sediment flooding is water and silt that moves through the flood-control system at Chico when creek flows run high. The basin was built in the 1960s, and a 2021 state notice limited the County's periodic removal of deposits. Calls are answered 24/7 and a crew dries the structure.
The Five-Mile Basin is a piece of flood-control infrastructure that the U.S. Army Corps of Engineers built in the 1960s. It takes peak flows off Big Chico Creek around central Chico and sends them toward Lindo Channel. A system like that does not simply move water. Over time it also collects the sediment that the creek carries, and that sediment is the part of the story most homeowners never see.
Sediment builds up in the basin during high-water events. A 2021 state notice limited how much of that deposit the County could remove on a regular schedule. The practical result is that the basin's capacity to carry water can change over time, and that is one reason a high-water event can behave differently from one season to the next. The County's own technical work is the place to read the detail.
For a homeowner, the question is not the basin's engineering but what the water and the silt did inside the house. If silt has entered a garage, a crawl space or a lower room, call (833) 490-5225. The line is answered 24/7, and a crew is sent as fast as one is available to read the damage and dry it.
The Five-Mile Basin is a flood-control basin built in the 1960s that takes peak flows off Big Chico Creek and sends them toward Lindo Channel. Sediment that the creek carries settles in the basin, and that deposit changes how the system carries water over time.
A basin slows the water it receives, and when water slows it drops the material it carries. Over many high-water events the material settles and forms a deposit. The deposit reduces the space the water has to move through, and it changes how the basin responds to the next high flow. That is why sediment is a concern for the system and not only for the creek.
For a homeowner, the same process shows up as silt in the places water reaches. The silt that the basin stops is the same kind of fine material that a crew finds in a garage, a crawl space or a lower room after a high-water event.
A 2021 state notice limited the County's periodic removal of deposits from the basin. The result is that sediment can stay in the system longer, and the effect on flow and on what reaches the city depends on how the basin is maintained.
The notice constrained the County's routine removal of deposits, and that matters because removal is how a basin keeps its capacity. When removal is limited, deposits can build up between events. A basin that has more material in it has less room, and that changes how high water behaves when it arrives.
The County's own technical documents are the authoritative place to read the detail. A homeowner does not need to resolve the engineering to understand the practical point: sediment in the system is part of why high water can behave differently from one season to the next.
Sediment is fine and sticky, so it gets into gaps and surfaces that clean water passes over. It holds moisture against materials and leaves a film that must be removed before drying can work.
Fine silt packs into the joints at the base of a wall and into the gaps around a door. Once there, it keeps the adjacent material damp, because it holds water in a way a clean surface does not. A floor covered in silt looks dry on top while the material underneath stays wet.
Silt also complicates the cleanup. A crew clears it with methods suited to fine material, because dry sweeping spreads it into the air and sweeping with household equipment does the same. The removal is part of the drying plan, not a separate chore.
A crew needs to see the water line, the deposit, the entry point and the materials that are wet. It records those on arrival and uses them to set the scope, which is explained and approved before work begins.
The first thing the technician looks for is the water line on the foundation and walls, because that line is the best record of how high the water stood. Next it finds the deposit and measures its depth where it can. Then it traces the route the water took onto the lot and into the house.
Those observations shape the scope. A thin film on a garage floor is a different job from a deep deposit in a crawl space, and the crew says which one it is before the work begins.
Price moves with the depth of silt, the number of spaces it reached, how many materials must be opened and how long the drying takes. No figure is given on this page, and the price is explained and approved on site before any work starts.
The first factor is how much sediment there is and where it sits, since a deep deposit in a crawl space takes longer to remove than a film on a floor. The second is how many spaces and materials it reached, because each one has to be opened and read. The third is the length of the drying needed to reach the dry target.
The crew explains each factor for your house and states the scope and the price before work starts. You can ask for the scope in writing and compare it with any written estimate you receive.
Do not walk through deep silt in a crawl space or a lower room, because the surface can give way and the air can carry fine particles. Wear a dust mask rated for fine particles and gloves when near loose sediment, and do not sweep it dry. Keep electrical equipment and extension cords off damp floors, and wash skin and clothing that touched silt before eating or sleeping.
The technician looks at the silt layer, its depth and its color, and at any line the water left on the foundation or the walls. Those marks show how high the water rose and how long it stood, which in turn tells the crew how much moisture reached the structure.
The crew walks the lot to find where the water entered and where it pooled. Low corners, window wells and the gap at the base of a gate are checked, because they are the places where silt tends to settle and where the next high-water event will leave it again.
Loose silt is removed while it is still damp, using methods suited to fine material. Left to dry on a floor it crusts and then lifts into the air when disturbed, and it also holds moisture underneath, so the crew clears it first.
Drywall and subfloor are opened at the points the readings show are holding moisture. The cavity is then dried from the inside, so the material behind the wall does not stay wet after the surface looks dry.
Drying equipment runs until the readings reach the dry target in the scope. The moisture log is kept throughout and given to the homeowner, so the record of the work is in writing.
A thin silt film is the most common result of a high-water event that reached a garage or shop. It is usually removed with damp methods and then dried. The crew checks the wall base and the door threshold, because silt that reaches those points can wick moisture into the bottom of the wall.
A crawl space or lower room that has collected a deep deposit needs more than surface cleaning. The silt and the soil beneath it hold moisture, and the framing above can wick water up from the deposit. The crew removes the deposit where it can reach it and reads the framing as it goes.
Silt that has built up against the outside of the foundation can channel water toward the gap at the base of the wall during the next rain. The crew describes what it sees, but it does not do exterior grading. It records the deposit and the water line so the homeowner has a clear account of the condition.
Tell us what's happening and we'll tell you honestly whether it's a quick fix, and what five-mile basin sediment flooding should cost.
Chico's sediment question is tied to Big Chico Creek and to the Five-Mile Basin, which the U.S. Army Corps of Engineers built in the 1960s. The basin is the reason creek water is handled at the city the way it is, and it is also the reason sediment matters to a house near the creek. A crew reads the silt it finds against that background.
A 2021 state notice limited the County's periodic removal of deposits from the basin. A basin that holds more material has less room for water, so a high-water event can arrive at a different level than it would have otherwise. Homeowners who want the detail can read the County's technical work, and the crew can speak to what it sees in your house.
After the Park Fire began in Bidwell Park on July 24, 2024, storm water carried more sediment off the burned ground. A basin that already held deposits and a burn that added silt to the flow are a combination that a crew takes seriously when it reads a house. The silt it finds is part of the record of how the water arrived.
Pumping creek water out of a Chico house before it soaks the walls, floors and subfloor.
Storm water that carries burn-scar silt into a Chico house, and how the damage is read and dried.
Removing creek and runoff water from a crawl space, and drying the framing before the floor is rebuilt.
Drying walls, floors and framing to a measured dry standard after a water loss in a Chico house.
Not sure if you're covered? Check your ZIP code.
After the Park Fire began in Bidwell Park on July 24, 2024, burned ground sheds rain faster and carries more sediment.
The Five-Mile Basin is a flood-control system that the U.S.
It is a flood-control basin that the U.S. Army Corps of Engineers built in the 1960s. It takes peak flows off Big Chico Creek around central Chico and sends them toward Lindo Channel. Sediment settles in it over time.
The notice limited the County's periodic removal of deposits, which affects how much room the basin has over time. Whether that changes flooding at a particular house depends on the water, the ground and the structure, and it is not something a homeowner can judge from the notice alone.
It is the same kind of fine material. Silt that settles in the basin is carried by the creek, and silt in a house is the same material arriving at the foundation. The crew reads what it finds and removes it with methods suited to fine sediment.
Sediment returns with each high-water event that reaches a low spot. The crew can remove it and dry the structure, but it cannot change the drainage around the lot. Ask the crew to describe the route the water took so you know where to watch.
Avoid dry sweeping and household vacuums, because fine silt spreads into the air. Keep the area closed off and let the crew remove the deposit with suitable methods. Photograph the silt before anything is moved.
The basin is a County and state system, and questions about its maintenance go to the agencies that manage it. The crew works on the house, and it can tell you what it found in the silt that reached yours.
The policy and the insurer decide what is covered. Keep the photographs, the crew's written scope, and the damaged materials, and let the insurer see them before anything is discarded.