Plugged Septic Field???

I reside in a city that still uses septic tanks. In July ’99 I purchased a 3 yr. old home
… and in August both 1000 gallon tanks were pumped out. My problems began last December … smell
… rotten chicken smell … absolutely bad! was detected. No reason for the smell could be located.
Eight weeks ago, a strong smell was present … and the gas company was called. Chico (my pooch) was
vomitting and I had an enormous headache. No gas, monoxide or anything else could be located by the
gas company. However, the smell in the dungeon (4.5 ft. cement crawl space) was horrid. No dampness,
water of any nature was located. One only of the 1000 gallon tanks was pumped … the smell
disappears. Now, it’s returned again. At $228.00 a pump (and that’s for one tank, it would be double
that to do both tanks) … it gets might expensive, should I be required to have the tanks pumped
every 8 weeks. Help!!!
I have a natural gravel based yard … digging any hole will soon let you know how many muscles you
really don’t have. When I purchased, the front yard was nil and void of any trees, flowers, grass
and now, … the entire yard was landscaped last October. So, I reckon that rules out tree roots. No
one here can supply any answers as to what the problem might be. Does it sound like the septic field
is plugged? in so short of time? (house built August 1996) I would appreciate any information,
comments or suggestions.
I thank you in advance.
Lois