Tanbark wood mulch separated by a dry creek bed, cement path, & brick retaining wall in a low-water San Jose yard.
May Day is a celebration of spring, but “April showers” were few and far between and it’s already starting to feel like summer! With another record-breaking hot year and the Bay Area in severe to extreme drought conditions homeowners concerned about water use and fire prevention are turning to gardening and landscaping for the solution. But a word of warning! Since updating my surprisingly popular post on mulch vs tanbark and the risk of termite infestation, I came across another reason to be cautious when applying it to your perimeter: fire.
Organic Mulches and Fire Hazard
Mulch can work wonders in a garden – it helps soil retain moisture, protects roots, reduces weeds, insulates the ground, can add nutrients and enrich the earth, adds visual appeal, and it’s affordable. It’s on every guide for landscaping water conservation (including Valley Water’s recommendations and San Jose Water’s tips)! Do a search and you’ll find it comes in a broad variety of materials. These can be divided into two groups: organic and inorganic. And organic matter can burn.
The University of Nevada Cooperative Extension has published their (easy to read) findings from a study comparing the combustibility of various organic landscape mulches. I recommend reading the booklet, but here are some of the key points I found most interesting: (more…)
The Silicon Valley liquefaction zones cover much of the Bay Area and Santa Clara County, but the risks are often not well understood or investigated. We know that this is earthquake country and tremblers are to be expected. But what difference does it make where you live or work – won’t the whole valley be shaking equally?
I’m a Realtor, not a geologist or geotech engineer, but I’d like to share some resources that may help answer some questions and provide avenues for further research on this topic.
What is liquefaction?
Liquefaction refers to the ground becoming liquified, or becoming fluid, during severe shaking. In 2010 and 2011, New Zealand experienced this and it made worldwide news. The Science Learning Hub website states that “During the Canterbury earthquakes of September 2010 and February 2011, liquefaction caused silt and fine sand to boil up and bury streets and gardens and caused buildings and vehicles to sink.”
Silty, sandy soil will respond very differently to bedrock in the case of extreme shaking. So no, the valley won’t all be shaking equally in the case of a large tremor. Liquefaction soils areas will get the worst of it. That’s why this designation matters so much.
What is a liquefaction zone?
After the Loma Prieta earthquake in 1989, the Department of Conservation, California Geological Survey created maps to make residents aware of areas in which there are increased risks from earthquake shaking due to landslides or liquefaction and to make sure that construction in those zones have extra investigation required. The liquefaction zones are noted by the state to be more dangerous due to the risk of the ground becoming liquid. You can learn more about these and related issues at the California Department of Conservation’s website. (more…)
Earthquake faults and flood plains are of interest to home buyers throughout the Golden State and to their lenders, too. Part of the home sale and home buying process is to provide information on these risk factors so that consumers (and their lenders) can make an informed decision.
Natural Hazard Reports are included in the disclosures when homes are bought and sold here in Silicon Valley. Those reports will indicate whether or not the property is located in areas with known natural hazards, including
- Flood Plains (100 and 500 year floods from heavy rainfall)
- Liquefaction Zones
- Earthquake Fault Zones
- Unstable Soils Areas (landslide areas)
- Flooding from dam failure zones
But wouldn’t you like to know where those places are before ever deciding where to target your next home?
You can! There are loads of tools online, including the Cal My Hazards Awareness Map, which is my go-to resource for many of the zones. This shows the state mapped fault zones, but NOT the county mapped ones. The county mapped fault zones, such as the Shannon Fault, will be listed in a Natural Hazard Disclosure link (though they may not always name the fault, only state that one is there). You can pull the county mapped geologic sites from this page on the Santa Clara County website (the map is about 30 MB btw).That’s a bit of a pain – you must download it and then read it using Adobe Acrobat to see the “layers” of natural hazards. Sorry – it is a slow process for accessing this information.
Another excellent site from the California Department of Water Resources provides Inundation Maps to let you know where flooding may take place from dam failure.
After doing some research on areas, you may want more information on how to mitigate the danger from seismic threats. There’s a booklet for that which is free: The Homeowner’s Guide to Earthquake Safety & Environmental Hazards. This info is so important that it is required that buyers be given it in escrow or before.
For sellers, it is crucial to understand any local hazards. If your home appears to be in a liquefaction area or flood plain, you need to know that the public may be eliminating your home for that reason. If that is bad info, you need to get the word out so that buyers don’t write off your home or worry about it when there may not be a concern. Or if your home is in a flood plain or fault zone, you need to realize it so that you get your home marketed appropriately, understanding that this could be impacting your market value.
Barclay’s Locaide County Map Books
The tool I miss most for my clients is the Barclay’s Locaide, which is almost impossible to find now.
Many of us Realtors used to utilize it pre-GPS to find our way to homes and neighborhoods, but also to know which zip code it was in, which school district, which MLS area, and of course which natural hazard zones, if any. On any given page, it shows all of the natural hazard zones except for liquefaction, which is shown on a county wife map at the front of the book. The front of the book also had county view pages showing the county and state mapped earthquake fault zones, unstable soils areas, etc.
The Barclays Locaide, which I believe was last printed in 2006, is difficult to find now but may be available in Realtor Board stores. As of this writing, it does not appear to be available to buy online, but keep checking just in case. A while back I found a used one that had been printed in 2000 – so they do show up sometimes.
The bottom line is that the info is all out there, but it may be piecemeal. The best solution is to have a great Natural Hazards Disclosure report for the property you want to buy. But before you locate the right house, you may want to target neighborhoods for house-hunting. That’s where it would be helpful to have those locaide maps for sale again.
Example of a Santa Clara Valley home with a creek behind the house. Not every waterway is scenic.
Silicon Valley has a bad case of “urban sprawl”, unfortunately, but there are places in San Jose and nearby where creeks meander through neighborhoods, offering a little extra space between back neighbors. This extra breathing room is valued by homeowners with a creek behind the house. They often cite the pleasantly rural sounds of frogs and birds as an added bonus.
But some home buyers are a little spooked. Are there risks with buying real estate next to a waterway? Would the home flood in heavy rains? Is there an excess of unpleasant wildlife to worry about? One of my buyer clients was concerned that burglers would use the creek’s access path to steal things and get away unseen. Another was afraid of cougars or bobcats or other unwelcome visitors coming in from a creek or tributary.
When Jim and I were newlyweds, we lived in a townhouse on Neary’s Lagoon in Santa Cruz (a bird sanctuary) and I have sold several homes along creeks or ponds, so will make some comments based on my experience.
Creek behind the house: scenic or not?
In general, I would say that being next to or near a creek most often will improve the value of the home because creeks are scenic and also provide a space buffer between rear neighbors. They frequently have beautiful old trees framing their banks and are slightly curved, too, so these are usually quite pretty. I won’t say that living next to a waterway which looks like a Los Angeles flood control channel would be beautiful or enhance a home’s value much, though the space between neighbors would still be appreciated. Each case must be judged on its own merits.
Wildlife at the water’s edge
It is true that there will be more wildlife near water, whether it’s a creek, river, reservoir, pond, or percolation pond. Birds, reptiles and animals need water and will seek it out. If you love nature, you may welcome the sound of frogs and geese, and perhaps secretly hope to see a wayward deer! If you decide to live near water, it is very important to make sure that wildlife cannot enter your home (chimney, attic and crawlspace included) and it will require some ongoing diligence to keep them out because they will be drawn to the water over and over again. I’ve known people adjacent to water to have some challenges with birds, bats, mice, rats, and other creatures trying to make their way in. But that can happen anywhere. At our current home, which is not next to or near a creek, we had a squirrel try to claw its way through flashing on our roof to get into the attic. Another time we had a possum or raccoon get into the attic. Be clear that being away from the water doesn’t mean “no wildlife issues” – but if you are next to water, you will probably face them a little more often.
Floods and flood plains – what is the risk if there’s a creek behind the house?
Creekside locations do not all flood; this is perhaps the biggest misconception. When buying a home, you can check the flood plain status via the Natural Hazards Disclosure Report, which the seller provides. You can also check online at the CAL My Hazards Awareness site. And please know that there are different types and levels of flood plains – they are not all the same! The one which requires flood insurance is called a 100 Year Flood Plain and in those locations, water of up to 1 foot may be expected once every 100 years (so not that often). There are 500 year flood plains and areas which are “dam failure inundation” zones (if a dam were to break, water downhill would flood, of course).
Protected species that depend on the waterways
We have a number of protected species in California, including certain frogs and salamanders. If your home (or the one you want to buy) is in the habitat area of those animals, birds, or reptiles, you may have some constraints on landscaping near the creek or water. Most of the time it involves not placing a fence within so many feet of the creek and using only native landscaping in that area close to the creek too. Just know that having a creek behind the house may carry extra responsibilities and restrictions.
As for crime, I would have to say that you want to always check a site like CityProtect.com or similar sources to know what’s happening. We do have crime everywhere, and all kinds, to varying degrees. Most creeks do not have easy access to people’s homes or yards, and often the service road along the creek is a rough gravel, so I have a hard time picturing burglers trying to get in and walk their stolen loot a ways down that path. But check the reports. Realtors are not crime experts and we cannot make promises about any area or location.
Valley Water depth to first groundwater in Santa Clara County
In most of Santa Clara County, home owners do not own the right to drill a well and pump groundwater under their property. That will be clarified in the preliminary title report (similarly, oil and mineral rights are usually not sold with residential neighborhood parcels here). The depth of the water may be of interest, though, as a high water table may have possible risks.
In come cases there could be problems with springs under the home. When that happens, the groundwater may percolate up under the house during times of heavy rains, causing water in the crawl space and possibly creating foundation damage later.
Another risk is underground water moving environmental hazards to your property. A plume of water could potentially move toxins released at a leaking underground storage tank (“LUST” site) to your property’s area, where you may be responsible for the cleanup! (For info on the leaking underground storage tanks, you’d want to read the JCP or similar report for natural and environmental hazards. That will tell you if there are any LUST sites within 1 mile of the property.)
Does your home, or the one you want to buy in the Santa Clara Valley, have a high water table? One way to learn is to check out the interactive map on the Valley Water website. Much or most of Campbell seems to have first groundwater at a depth of 50 to 100 feet. Much of the low-lying areas of San Jose and Santa Clara have water at a mere 0 – 10′!
The interactive map that I saw includes most, but not all, of the valley. Enjoy checking it out!
Santa Clara County Depth to First Groundwater
Historic Homes, Willow Glen, Foundations and Red Flags
Why are the hardwood floors cupping?
January is National Radon Action Month. Californians can get a free test kit here https://www.cdph.ca.gov/Programs/CEH/DRSEM/Pages/EMB/Radon/Radon.aspx
While there are many natural hazards that are commonly discussed in the San Jose area, such as earthquake faults, flood planes, and liquefaction zones, there’s one which comes up frequently on the east coast but is largely ignored here in the Valley of Heart’s Delight. The question is this: is there a radon risk in Silicon Valley homes?
First, though, what is radon?
Per the EPA website, “Radon (chemical symbol Rn) is an odorless, colorless, radioactive gas. It comes from the natural decay of uranium and radium found in nearly all rocks and soils. Radon can move up from the ground into buildings through openings in floors or walls that are in contact with the ground.”
If the idea that a radioactive carcinogenic gas can enter your home or workplace completely unnoticed spooks you, that’s understandable. Thankfully, it is uncommon to find radon at high enough concentrations for concern in Silicon Valley. It’s helpful in that regard that it’s a region with few smokers and few basements, both of which can increase the risk.
That being said, radon can be found all over the world, and similarly, homes high in radon can be found anywhere, though they are more or less common depending on where you are.
So how do you know your radon risk?
Santa Clara County is considered to be a moderate, and not high, radon area. Different geological conditions may make an area more or less prone to high levels of radon gas, though, so even here it is possible to have a radon risk.
The U.S. Environmental Protection Agency (EPA) and the U.S. Geological Survey have mapped by county the average potential radon levels in the area, divided into three zoning (Level 3 being the lowest and Level 1 the highest average measurement zones) for buildings without radon remediation. Santa Clara County is a Zone 2 area per the map linked to above. Check the map at Berkeley Lab Columbia Univeristy Radon Project page. Areas with the greatest risk, and which suggest remediation, are those in Zone 1. The are counties with predicted average indoor radon screening levels greater than 4 pCi/L.
If you would like to check your home’s radon risk levels, there are two tests you can use to measure indoor exposure: a short-term test and a long-term test, and both are affordable. The short-term test only takes a few days, might cost around $15, and is a less reliable way to get results quickly. Long-term measurements take a year and uses detectors placed one on each living level of the house (so approximately $25 for a single-story, $50 for a two-story home). These are much more accurate, so they are the ones preferred by researchers and home owners, but the results will take longer to reach and the cost is higher.
Worst-case-scenario, you have measured 4+ pCi/L (picoCuries per liter of air), the level at which the EPA recommends remediation. Now what? Prepare to spend a few thousand dollars (a great bargain to keep you and your family healthy). The standard treatment involves the installation of a pipeline and fan system which will pull the seeping gas from the ground beneath your house and redirect it outside where it can disperse safely in the air. The only apparent downside to this procedure (other than the time and cost of installation) is that your heat and air conditioning costs may rise slightly. Check with the experts, though, to get the full scope of both the risk and the remediation impact.
Read more at the pages listed below.
If you are thinking of buying a home in Silicon Valley, there are things you want to know upfront so that you make an informed decision. Because the most important factor is “location, location, location”, and because once you buy a home you can’t change it, you’ll need to know some location-specific things, including:
- where are the earthquake fault lines?
- where are the geologic hazard zones, such as liquifaction areas?
- where are the flood plains?
- where are man-made things that will negatively or positively impact a home’s value? Things such as
- train lines
- high voltage power lines
- school district boundaries
- zip code boundaries
- proximity to entertainment venues
When looking at maps, sometimes these items show up and sometimes they don’t. Realtors and other real estate professionals in the San Jose area often use a Barclay’s Locaide to locate the natural hazard areas. Google maps can help uncover some other areas, but sometimes it raises more questions than it answers. (Last year a Realtor who doesn’t know the Belwood of Los Gatos area too well phoned me to ask what the object showing up in the hills of Belgatos Park was – it is just a covered resevoir, but it was not identified on the map and concerned some buyers. Local knowledge is still very helpful.)
Tonight I spent some time zooming in on Google Maps, using the satellite view, and idenified many of the paths of the high voltage power lines running through Los Gatos and nearby areas, such as Saratoga, Cupertino, Almaden Valley, Santa Teresa, and South San Jose.
Below, please find the fruit of that labor. I do not claim to have tracked all of the high voltage power lines in the west valley area of Santa Clara County, but I think I got many – maybe even most – of them. I hope you find the information helpful!
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