Lemmon Valley sits beside Swan Lake in a closed basin, and part of it is mapped floodplain. For below-grade work, checking your parcel’s current designation is not a formality.
No obligation. Every estimate starts with a walkthrough and a straight answer about what your basement will allow.
Lemmon Valley shares a census designation with Golden Valley covering about 32.5 square miles north of Reno, and it contains the Swan Lake Nature Study Area, a wetland that supports a substantial bird population. The wetland is the clue: this is a closed basin, and water that arrives here does not drain away to a river.
Washoe County has remapped the Swan Lake and Silver Lake floodplains using more recent data and mapping techniques than the studies behind the previous maps, which dated from 2009. At Swan Lake the updated mapping puts roughly 154 residential properties inside the 1% annual chance floodplain: about 123 that were already in it, around 42 newly added, and about 11 removed. A small number of commercial and government properties were added as well. At Silver Lake around 50 residential properties are in the floodplain with none newly added and four removed.
For anyone thinking about finishing a basement here, that is the first thing to establish, and it has to be your parcel rather than your neighbourhood. A designation you remember from years ago may no longer be current, and it can have moved in either direction. It affects what is permitted, how it has to be built, and your insurance position.
Beyond flood mapping, the closed-basin character shows up in ordinary ways: how surface water moves during a fast melt, where an egress window well can safely go, and whether a sump and discharge route is worth building in while the slab is accessible.
The Swan Lake mapping was updated with newer data than the 2009 maps. Roughly 42 residential properties were added and about 11 removed, so an old assumption is not reliable in either direction.
Water here has no river to leave by. Grading, downspout discharge and window well drainage matter more than they do in valleys that drain to the Truckee.
Even where there is no current water problem, a basin and discharge route is far cheaper to install during construction than to retrofit into a finished floor.
All six are available across Lemmon Valley. They differ because the problems differ, not because the wording does.
A full basement taken from bare joists to finished rooms: framing, insulation, electrical, drywall, flooring and trim.
Read more →A legal sleeping room, which means a compliant egress opening and the ceiling height to go with it.
Read more →Adding or rebuilding a bathroom below grade, where the drain line decides most of the layout.
Read more →An open family room built around the beam, the stair and whatever daylight the space actually gets.
Read more →A room planned around sightlines, seating rows and sound isolation before a single stud goes up.
Read more →A quiet, well-lit workspace with enough circuits and data to run it, and a door that closes.
Read more →Not automatically, but it changes what is permitted, how it must be built and what it does to your insurance. This needs settling with Washoe County before design work rather than after.
The county’s updated Swan Lake mapping replaced studies dating from 2009, so get a current determination for your parcel. Around 42 residential properties there were newly added to the 1% floodplain and about 11 were removed, which means old assumptions can be wrong in either direction.
Washoe County publishes the floodplain mapping and runs a regional mapping system that will resolve a parcel number to its current status. The county’s engineering and capital projects team handles the Swan and Silver Lake mapping specifically.
It is worth doing this yourself early rather than relying on a contractor’s recollection, including ours.
It does not necessarily rule it out, but it absolutely changes the approach. A history of water means the priority order shifts: understand the path, manage the water, then finish, in that sequence.
What we will not do is insulate and drywall over an unresolved water path. That converts a manageable problem into an expensive one hidden behind a wall.
Washoe County, since the area is unincorporated. The county adopted the 2024 International Residential Code with the 2024 Northern Nevada Amendments effective 1 July 2025 and its Building Program is on (775) 328-2020.
Where a parcel sits in mapped floodplain there are additional requirements layered on top of ordinary permitting, so confirm the full picture for your address before planning around a timeline.
In this basin it is at least worth discussing, even where you have never had water. Installing a basin and a discharge route while the slab work is happening costs a fraction of retrofitting one into a finished floor.
Whether it is actually justified depends on your parcel, its grading and the flood mapping. We would rather look and tell you it is unnecessary than fit one by default.
Send photos and rough dimensions and you will get a straight assessment of what that basement can hold, what the work involves, and what it is likely to cost.