Testing & Government Oversight

Before starting to develop Runkle Canyon, our team responded to community feedback calling for the selection of an independent body to conduct additional testing in Runkle Canyon and oversee the site’s scientific review. Community members requested the California Department of Toxic Substances Control (DTSC) be involved in verifying the safety of our site for homes. We agreed to that request, and diligently and transparently followed every step of the process required by both the DTSC and the City of Simi Valley to move forward with the development.

After careful and extensive scientific testing, the DTSC concluded in 2010 that the soil in Runkle Canyon is safe. These results were confirmed by DTSC’s own team of scientists and laboratories.

The California Department of Toxic Substances Control, The City of Simi Valley, Lennar Homes and KB Home have all concluded Runkle Canyon is safe for residential living. The conclusions were derived by reviewing all the scientific data from soil sampling performed on the property. We are providing the same data to you so that you can make your own informed decision.

Figure 1

Figure 1 shows the individual sampling results of all 255 strontium-90 soil sample analyses from Runkle Canyon made at various times from 1998 through 2010 There are two ‘sets’ of soil samples that were conducted – one from 1998-2000 and another from 2007-2010. The earlier results showed slightly higher levels compared to the more recent samples. The 1998-2000 samples were conducted without regulatory oversight. The 2007-2010 samples were conducted with oversight by the California Department of Toxic Substances Control (DTSC).

In an effort to replicate the earlier, elevated results, in 2005, the California Department of Public Health (DPH) re-tested several of the precise locations where earlier samples had shown the highest results, which are all on the part of the property outside of the area of residential development. DPH found significantly lower levels in those locations, 9 of the 10 samples being below detection limits. Because the precise resampling was unable to replicate the elevated levels shown earlier, DPH’s results called into question the earlier methodology.

Although the DPH was unable to duplicate the earlier, higher results, Runkle Canyon, LLC did not dismiss them, but undertook extensive additional soil sampling in 2007 and 2010. The subsequent soil sampling, which used updated and stringent methodology, showed much lower levels compared to those found in earlier sampling.

Figure 1 also shows the results of 129 U.S. Environmental Protection Agency (US EPA) soil samples taken in 2009 from various areas in Southern California, including Santa Clarita, the Santa Monica Mountains, Topanga State Park, and Los Padres National Forest. The US EPA tested these areas in Southern California to determine at what levels both strontium-90 and cesium-137 occur naturally in the environment (e.g. background levels). The 2007 and 2010 results from Runkle Canyon are consistent with the findings of the US EPA in its regional background sampling.


To help better understand these results, the figure below also shows three lines that provide additional information. These lines represent soil sample results in comparison to other areas in Southern California and US EPA risk calculations.

Line 1: Background Determined by US EPA

Line 1, represents what the US EPA considers to be the “background level;” that is, the level of strontium-90 that is inherently present in the environment in Southern California.

Line 2: Resident (Default - Homegrown Produce Scenario)

Line 2 represents the US EPA’s most stringent safety threshold for residential use, which would apply to a resident who spends over 95% of his or her time on the land, consumes a diet comprised of hundreds of pounds of fruits and vegetables grown annually in the backyard, and ingests a high amount of soil. Note that almost all of the sampling from 2005 forward falls under this threshold.

Line 3: Resident (No Homegrown Produce Scenario)

Line 3 represents the same US EPA safety threshold for residential use as Line 2, except that residents are assumed not to consume produce grown on the property. This is the scenario that most closely reflects the Runkle Canyon residential use. Virtually all the results, both new and old, fall beneath this line.


The combination of the soil sampling results from 2007 through 2010 led the DTSC to give the site a clean bill of health for residential occupancy – this finding was confirmed in a letter from the DTSC dated December 17, 2010 (http://www.runklecanyon.com/runkle/wp-content/uploads/2015/11/DTSC-No-Further-Action-Letter-2010.pdf). Based on this determination and extensive consultation with experts, Runkle Canyon, LLC concluded that it was safe to build homes.

Figure 1

The groundwater in Runkle Canyon was tested for its safety for years by the California Regional Water Quality Control Board, which concluded in 2007 that it met safety levels and no further monitoring was necessary. Recent studies have shown that no groundwater contamination has migrated from SSFL to Runkle Canyon.  Nevertheless, no homes at Runkle Canyon will use groundwater for consumption: like other homes in Simi Valley, Runkle Canyon’s neighborhoods will be connected to municipal water sources which, in addition to being safe, are more cost-efficient and reliable. 

Using all of this data to determine Runkle Canyon is a safe home for future residents, the City of Simi Valley approved the scientific review of Runkle Canyon’s safety as an addition to the Environmental Impact Report in 2012. Since 2012, the city moved forward with issuing the necessary permits for the development to be completed.

Setting the Record Straight

There is no substitute for verifiable scientific data and government approval. And the data is clear: Runkle Canyon is just as safe as nearby areas in Ventura and Los Angeles counties.

Our database of scientific reports and government documents provides additional details and data demonstrating Runkle Canyon’s safety.