OUR GEM: Hold Your Ground! A case for good construction site planning
Erosion control is a critical aspect of responsible site development, especially in areas with steep terrain and heavy precipitation, which is often the case in North Idaho. This case study highlights the challenges faced during the development of a hillside property near Hayden Lake and the efforts to address consequences of inadequate initial planning.
Background
In 2021, two properties on the hillside above Hayden Lake underwent development for residential projects. The upper site above E. Hayden Lake Road was for the development of a single-family residence and featured a long, switch-backed driveway, as is common in our region. The driveway was designed by an experienced contractor in land development. There was no professional engineering at this point of development, though, and runoff from the steep slopes was not thoroughly analyzed. Plans included a narrative for BMPs. However, due to the steepness of slope and lack of detailed analysis for the risks associated with this difficult site, proper BMP installation and management lacked focused attention and proper placement.
To manage stormwater runoff, a rock-lined ditch and two infiltration areas (aka: swales) were constructed. Small sections of silt fence were also installed. The heavily forested slopes were cleared during construction, leaving the soil exposed and vulnerable to the forces of wind, water, and gravity. This served as a catalyst for the devastation by the weather event which followed.
The lower site, east of E. Hayden Lake Road, featured development to realign a road for the purpose of future homesites. The site had an engineered plan in place with approved stormwater calculations and designs for BMP placement.
The Problem
Following initial site development and hillslope disturbance on both parcels, a rain-on-snow event triggered significant stormwater runoff from the upper parcel to the lower parcel with a cascading effect. The amount of water produced by the storm, combined with residual snow, overwhelmed the erosion control measures on the upper parcel sending overpowering water and sediment to the lower parcel, causing significant failures of the BMPs.
The runoff breached a series of swales, check dams and culverts, resulting in a large plume of sediment-contaminated runoff flowing downhill into Hayden Lake. The turbidity could be seen approximately a half mile into Hayden Lake. The impacts of polluted runoff entering water bodies are well documented – sediment alone can be damaging to water quality, aquatic habitat, and fish survival, in addition to other pollutants the sediment and stormwater runoff can carry into the water with it.
These impacts to downstream water quality could have been prevented with more planning, design, and the proper implementation of best management practices (BMPs) for erosion prevention. While this story is a pronounced example of risks to our water resources caused by improperly implemented BMPs, even small contributions can become large collective impacts. Smaller projects with less obvious impacts can be detrimental to water quality in our region.
The Solution
The upper parcel landowner eventually hired an engineering firm with staff knowledgeable in erosion, sediment, and stormwater control techniques to stabilize the steep slopes and reduce runoff impacts. Although it took more time and money to eventually get a handle on the issue, the site was eventually stabilized.
Unfortunately, the problem did move downslope, and that impact is ongoing. The lower parcel owner had to conduct massive repairs of his site, re-establish BMPs and adjust culvert placements along the re-aligned road.
The best long-term solution is prevention. Whether you’re building something small like a shed or a summer cabin, or tackling a larger, more complex project, it’s smart to bring in a professional who understands stormwater BMPs before any ground is disturbed. It’s much easier—and more cost-effective—to protect vegetation and soil from the start than to try to fix erosion problems after they’ve begun. Look for someone with planning and engineering experience who also specializes in erosion and sediment control. They’ll understand how to manage stormwater runoff both on and around your site, helping you avoid future headaches, added costs, and possible fines.
Panhandle SEEP
The Panhandle Stormwater and Erosion Education Program (SEEP) is an education program offered in the Idaho panhandle since 2007. It’s a good resource for contractors, planning professionals, and anyone interested in learning more about BMPs to prevent erosion, contain sedimentation, and manage stormwater runoff during and after construction. For more information about Panhandle SEEP, check out this website: Stormwater & Erosion Education Program – University of Idaho. Whether you’re planning a small dig on your property or a significant re-shaping of the land, you can also turn to the SEEP website to find your next certified contractor. Access a list of SEEP-certified individuals on the website: SEEP Certification – Stormwater & Erosion Education Program (click on Current SEEP Certificate Holders under Related Documents).
