NewHomeShopper,
I dealt with that issue over a year ago.
I was set to buy at Los Colinas.
At first, I researched the landfill issue, but could not determine the exact distance from PS. I somehow came to the conculsion that it was several miles away, and felt better.
Later, however, I found out that it was considerably less than 1 mile from the Los Colinas neighborhood.
That changed my mind, and I did not buy there.
My reasoning:
1. Fear (rational or not) of contaminants shifting with groud water deep below the land, and
2. Fear of future bad publicity, or worse, lawsuits.
3. I worried that under the right weather conditions, the odor might travel.
I honestly think it's safe, but it is still percieved as a negative.
I've compromised on homes before (too close to busy street, no view when competition has, etc.) and have vowed to avoid potential negatives in any property I purchase again. There are too many other choices out there.
Look at all the homes in Ladera either under, or in full view of high-voltage power lines. When the buyer pool contracts, and that buyer has 20 other homes to choose from that are not under the lines, chances are that home will sit.
You admitted to worry - that should tell you everything you need to know!
Having said that, I think Sendero is slightly less affected, because it's on the other side of Portola.
You have many good options now - if you buy with your head, as well as your heart!