Manhole covers are generally made of steel and are quite heavy. In fact each year many American Utility Workers are injured due to the heavy covers. Fingers are crushed, heads banged and backs sent out of alignment. Today some cities have gone to replacing the manhole covers with synthetic or composite covers which can take the same amount of weight without cracking, do not rust, weigh considerably less and are not stolen to turn in for scrap metal. Some larger cities lose some 100-300 manhole covers per year from theft, many of these manhole covers turn up at metal recycling yards. Iron manhole covers often rust sending orange-ish mud and debris into underground utility holes and cause damage to components and contamination of ground water and urban run off storm drains with iron oxides.
There are a couple of innovative companies already making these manhole covers from composite materials and many cities are opting for the stronger, lighter and more durable materials. Here are a couple of websites to learn more:
http://www.ebw.com/products/ust-ast/pdf/FRC_30_36_42_Manholes.pdf
http://www.hermelock.com/
One thing which has not been discussed is that since composite it made in layers, sensors can be contained within these units or covers. Sensors to detect underground gases alerting crews of toxicity or bad air, which is another killer amongst ground utility workers, can be easily molded into the covers. Sensors such as traffic counters with satellite relays can tell us of congestion, weight of vehicles and other important road maintenance upgrades needed. Sensors can also alert us of forced entry into our underground utility systems to protect against international Terrorism attacks. The new innovations in materials is well known in many industries such as aerospace, but we should also be looking at its uses underground because the sky is not the limit for these new composite polymer based materials. Think on this.
"Lance Winslow" - Online Think Tank forum board. If you have innovative thoughts and unique perspectives, come think with Lance; www.WorldThinkTank.net/wttbbs/