The Challenges of Developing Land in King County
“What can go wrong?”
(my former boss)
When I moved from the city to the country - unincorporated King County - designing a home for a client became a far more complicated problem. Undeveloped lots face a number of challenges just to become feasible to build. If you are buying new property in King County, or if you already have, this guide will help you sort through the madness.
Before you buy a new lot, ask for up to 60 days to perform a feasibility analysis. Hire an architect to walk the property and lend their professional expertise to a number of issues, from providing water and sewer, to working around environmental areas, to evaluating the zoning code of the local jurisdiction. You want to know the dark secrets before you buy.
Here is an outline of the chief issues with new lots:
#1 Septic
When a connection to a sewer system is not available, a rural lot cannot support a new home unless there is a feasible septic system. In King County, there must be enough area for both primary drain field and an equally sized reserve area. This often means you must have about 3,000 sq. ft. available. The first thing I do when evaluating a new lot is to hire a septic designer to perform feasibility.
Green Tip: Although composting toilets may be approved (the State of Washington keeps a list of approved systems) they do not lessen the septic area requirement, because the assumption is that a future owner may not want the hassle of a composting system.
The septic designer will need to do some soil test pits to evaluate the soil. They may also need to dig some test holes and allow rainwater to naturally fill them during the rainy months to prove to the King County Department of Health officials that the soil is infiltrating as needed.
The drainage field must obey setbacks from environmental zones like streams and wetlands, and cannot be placed on steep slopes (of 40% or more, a drop in 4 feet for every 10 feet). However drainage fields may often be placed within unbuildable areas adjacent to steep slopes. You can get a preliminary idea for the slopes by looking up your lot on the King County IMap.
#2 Water
If you have a rural lot, it is possible that you may have a connection to district water. On islands in which there is a single-source aquifer, water may be scarce. Even if there is a connection to district water, is important to know if you have a water share, and if your share has already been paid for (usually there is a substantial fee at the time of connection). Even if you have the right to purchase a water share, you may be waitlisted in perpetuity.
If you don’t have district water, you will need a well. Look at the size of your lot; if it is over 5 acres, you are golden, but if not, you will need to know when your lot was created. If it was created prior to 1972, you are still allowed to drill a new well. If not, you have a problem.
Some lots come with an easement (referenced on your deed) that allows you to connect to a Class B well that serves multiple lots. These wells are substantially more expensive to create and maintain because they must provide water that meets a minimum level of quality, a max threshold on contaminants like arsenic. For single family wells, your septic designer can submit the paperwork. But for a shared well, you will need to hire a well engineer.
New wells also require a 100 foot setbacks from property lines (unless you obtain an easement) and all man-made structures (except the pumphouse). Driveways are OK. The total area of a 100 foot circle is 31,450 sq ft (3/4 acre). This eats up a large, contiguous area of a rural lot. The well head must be accessible to a drill rig, so you may need to build a temporary driveway with quarry spalls (large crushed stones).
Green Tip: A friend tells me that it is now feasible in King County to approve a rainwater catchment system as a primary water source in lieu of a new well. I have to see it to believe it.
The well and on-site septic applications must be submitted to King County Public Health but need not be approved yet to submit your building permit application. The permit cannot issue until a verified water source is in place.
#3 Environmental Hazards
When you acquire a new lot in King County, look for areas on or adjacent to the site mapped as “critical areas” such as slopes, rivers & streams, wetlands, landslide hazard areas, and so forth. Even if nothing is mapped, you will need to hire a geotechnical engineer and/or an environmental consultant to walk the site and provide a report to the county saying so.
Sometimes, the consultant will find something, and it is important for them to take special care in delineating exactly what is going on, and how big it is, as their interpretation is often accepted by King County reviewers. At which point the county issues a “Critical Area Designation” (CAD) that spells out the requirements for a project.
Note: I have seen CADs issued by King County that reference “further investigations” before making a commitment to a setback. Take this as a warning. You do not want to start a project without a fully unambiguous setback.
King County has an obligation to allow private land owners to utilize their land. When the setbacks from environmental features interfere with buildable areas on the lot, there is a process for obtaining reductions in setbacks in exchange for mitigation measures. I have found this process, called: “Critical Area Alteration Exemption” to be cumbersome, very slow to navigate, and expensive.
Note that drainage fields are governed by King County Public Health, and have a separate set of requirements to those governed by King County zoning for buildings. They also have a different way of classifying wetlands and streams.
Here are some environmental hazards:
Wetlands
Wetlands are sneaky. A field that is bone dry in July may have standing water in the winter. The resulting soggy soil may support wetland plants and be a protected zone with buffers up to 100 feet or more. I can often spot a wetland but it is not always obvious.
Rivers & Streams
When I was 10 years old, I fell in love with Frank Lloyd Wright’s Fallingwater House, perched over the Bear Run River. Long gone are the days when we could build over streams, or even near streams. We have discovered that this is bad. Protected corridors around rivers and streams protect the water quality that allows life to thrive. Even seasonal streams may have buffers of 50-100 feet or more.
Slopes
Slopes require setbacks. If you are adjacent to a slope, you will need to hire a geotechnical reviewer to test the soil, sometimes with a drilling rig. Often, the most beautifully scenic bluffs are those most worrisome. Some may require setbacks of up to 65 feet. Note that a survey is very useful as you can easily delinate on the contour map where steep slopes exist.
Landslide Hazard
Similar, but not identical to slope hazards, are landslide hazard areas. Geotechnical engineers will look for long-term shifting of the soil and offer recommendations. You want these recommendations to be in your favor, and a good geotech will both be frank about the concerns as well as offer you the best recommendation possible given the nature of the site.
seismic hazard
Another soil issue, seismic hazards are often more common in urban areas in which previous grading activity has moved earth around. This “fill dirt,” if it is not properly compacted, will liquify during earthquakes. That is not good.
You may require piles or pin piles as part of your foundation design. These are metal columns driven into the earth that support your building directly on bedrock. Additional concrete may also be needed to create grade beams spanning between piles. All of which increases the cost of the foundation.
#4 Restrictive Easements
Before you buy property, read your deed. If you don’t understand it, ask someone to help you interpret it. If you don’t read your deed, you may be surprised that someone has loaded your property with restrictive easements that serve other lots. I have seen a lot loaded with easements to provide space accommodating wells and drainage fields for three adjacent parcels. The owners were clueless.
How could this happen? The real estate agent was clueless, and there is no professional standard requiring them to be anything else. This is why it is so important to have your architect perform a feasibility study on a new lot.
#5 Soil Infiltration
All the water that hits a man-made surface, such as a paved road, or a roof, must be dealt with according to the rules laid down in the King County Stormwater Manual (KCSM). The cheapest way of treating this water is to disperse it. However, dispersion may require a “flow-path” of 100 feet of gentle slope that is designed to remain naturally vegetated, and these areas must have setbacks from drainage fields.
Other kinds of systems will directly infiltrate stormwater into the ground. The ability to do so depends on the type of soil. You may need to have the a geotech perform a “pit” infiltration test to determine the infiltration rate. For sites that poorly infiltrate, you may be faced with costly requirements for underground water detention.
Green Tip: Green roofs naturally slow down the rate at which water flows off the roof, and they can be utilized by the KCSM for avoiding costly underground detention.
For sites that are highly constrained by environmental hazards, early coordination with a civil engineer is important to understand feasibility.
#6 Fire Sprinklers
Sprinkler systems are often required in rural projects. If your driveway is too long, to narrow, or if it doesn’t have a good turn-around for the fire truck; or the distance from the parking area to all sides of all structures is more than 150 feet, then you will likely need sprinklers. Further, the drag line from the nearest hydrant cannot be too long. Sprinklers will likely add about $25,000 to a project, and you may need to incorporate storage and pumps into your well pumphouse, or provide for tank storage if the flow rate from your water service is not sufficient to meet “fire flow.”
In Conclusion
Before purchasing an undeveloped lot in King County, have a professional perform a feasibility analysis that addresses all of these issues. Most sellers will recognize the need for a period of 30 to 60 days for this process.
In order to help get a sense for the up-front “soft” costs of developing land, let’s imagine that you recently bought a 5-acre parcel with some wet areas and some slopes. You wanted to button up all the unknowns prior to designing a new home. The land cost $200,000 for a scenic, forested parcel.
$5,000 Architect Feasibility Study & Site Planning
$5,000 Survey
$5,000 Wetland Delineation
$2,000 Critical Area Designation Fees
$5,000 Infiltration Testing
$5,000 Septic Design Fees and KCPH Submittal
$5,000 Geotech report
$32,000 Subtotal
At this point, you will still need to design a home for your lot. For a $1M custom home, fees for these services might constitute:
$50,000 Architecture
$10,000 Interior Design
$7,500 Structural Engineering
$7,500 Civil Engineering
$75,000 Subtotal
To relate these to the value of your $1M construction project, you are spending an additional 20% on the land, 3.2% on feasibility, and 7.5% on design and engineering.
At AirMod Architecture, we don’t love developing land, but we do love helping our clients realize their dreams. As a result, we take the land development process very seriously. Our feasibility report is our warranty that your project can be built.
Sincerely,
Brett Holverstott