Spongy Grass Garden ?

[planeloco]

We live in a very quiet hamlet in North Wales. We ONLY have Bottled GAS or GAS TANKS, NO Mains GAS here.
Some 17 years ago my neighbor, 3 doors away decided to have a GAS TANK in her garden. This garden was a slope roughly 6 feet in height from top to bottom over a 15 foot spread. I remember that she had a BIG HOLE DUG & the tank was placed into it. Round the tank she had rubble put in topped with soil & a nice FLAT GARDEN spreading about 10 feet then ROCKS to finish it off across the front & both sides. She called me over today to ask my opinion as the TOP GRASSY BIT is like walking ON SPONGE. She lifted the top off the tank where the GAS WAGON fills it, although it stunk to High Heaven there was no sign of WATER ?? The smell was PROBABLY THE GAS itself ? Can Any ABers give a pointer as to what may be happening here please ? Bearing in mind that we have had very little rainfall over the past 12 months, especially the WONDERFUL Summer in 2014. When I stood & pressed the GRASS / MOSS there was no sign of any water. Thank You ALL in Advance for any help.

[woofgang]

Why all the CAPS?

[hc4361]

If there is a lot of moss it will feel very spongy

[Gizmonster]

I was going to suggest moss as well .....

[planeloco]

diolch yn fawr, tara rhwan.

[hc4361]

Tara to you, too

[BRIGHT SPARK]

You will get a certain amount of propane smell below the filler cover,however if its excessive get it looked at.Is it her own tank or is it supplied by Calor.Either way it needs inspecting.Tell her to call the gas supplier and voice her concerns.Sunken tanks do have a finite life and should be inspected annually.If it is leaking the supplier will empty the tank and refuse to refill until faults are rectified. Calor no longer sell tanks, they only rent.All future issues are then rectified by Calor.Rental is around £100 per year....£1000 to install a sunken tank and f.o.c. for an above ground tank.