Coal mining generates significant adverse environmental impacts. Historically, coal mining has been a very dangerous activity and the list of historical coal mining disasters is a long one. Underground mining hazards include suffocation, gas poisoning, roof collapse and gas explosions.
The term 'OVD' (Optically Variable Device) is used to describe both laser generated hologram images and electron beam generated images. These optically variable devices are created in highly-secure facilities and are at the forefront of overt asset and brand protection programmes.
The International Residential Code (unmodified) requires a finish floor elevation 6 higher than the Base Flood Elevation (BFE). NAVD is the North American Vertical Datum. if the finish floor is listed as 7.0 NAVD then the finish floor should be 3.5' above the benchmark elevation of 3.5 NAVD. 7.0 NAVD - 3.5' NAVD = 3.5' difference. Don't know if I explained this or confused you, but hope it makes sense.