take them to australia. >> that is right. and thanks for joining us. tonight on "world news" -- investigating the inferno. the latest on what caused that pipeline explosion. and with 2.5 million miles of pipe in america, how to know your neighborhood is at risk. tackling taxes -- 50 days before the election, will you really end up paying less or more? bruised brains among kids who play basketball. why is the danger even greater for girls? and a hero's story -- he's getting his medal of honor. and we have that first interview about that life-changing moment of courage. good evening. we can't see them but they are everywhere crisscrossing america -- 2.5 million miles of natural gas

pipeline, enough to circle the earth 100 times. tonight, we have the latest on the investigation into the california explosion, as stunned residents there head home to see what's left of their neighborhood. neal karlinsky tells us how investigators are looking at the age of the pipes and piecing together the clues. he's in san bruno again this monday for us. good evening, neal. >> reporter: good evening, diane. people in the neighborhood where i'm standing right now have just been let back in. but the real damage is just down their street here. take a look at this wasteland that used to be a neighborhood. now, people who live down there still aren't allowed to go back in. instead, it's filled with investigators who are still trying to figure out exactly why this happened. the natural gas pipe that leveled this neighborhood was packed up and trucked out by the ntsb today as their most critical piece of evidence, even as neighbors just down the

street are finally returning home. >> what the [ bleep ] happened? >> reporter: the people who live on the street where this incredible home video was taken are still nervous, and the sight of pg&e workers using electronic sniffers to check for more leaks under their street isn't helping. >> i feel secure, but she's not. she's scared. she keeps telling me, "i don't wanna come home, mom, i don't wanna go home." >> reporter: investigators so far have two areas of concern as they examined the pipe which was first installed in 1956. first, that it has a long seam where it was welded together and may have been susceptible to corrosion. but they've also found a hodgepodge of small pieces called "pups," each individually welded in place to help the pipe make a dip under the road. more modern pipes are simply bent to shape, which leaves fewer weld points that could fail, then catch fire from something as simple as a nearby stove or car. a microscopic examination will look for an answer. >> was it, for example, a fatigue fracture where, you

know, the pressurization, depressurization bends it back and forth and back and forth, until it eventually breaks? or was it a fracture from impact, from excavation? >> reporter: and investigators now say they have found no hard evidence that neighbors formally complained about the smell of gas leading up to the blast. >> the real question is did it need repair, when is the last time it was expected, and it was inspected as early as march 2010. >> reporter: meanwhile, residents who suffered only minor damage are just trying to clean up and get their lives back in order on a street that is still anything but normal. >> and from neal karlinsky at the scene of that blast in california, we turn, now, to a question everywhere was asking all weekend long -- is there a way to know if there's a natural gas pipeline running under your house and how big is it, how old? barbara pinto tells us how some people found out. >> reporter: the incidents happen every other day in this country. >> it's something we need to get a clear handle on before it gets worse. >> reporter: in this san diego

neighborhood last night, more trouble seeped from underground. the frightening smell of natural gas forced dozens from their homes. and in illinois, hundreds of workers scrambled to contain crude oil that gushed for three days from a ruptured main. often, as in friday's tragedy in california, residents say they have no idea what was beneath their homes until it was too late. this, despite the fact that utilities are required by law to clearly mark pipelines and notify residents about those aging neighbors they don't see. here in the chicago neighborhood, residents share this street with an underground natural gas pipeline but there's no evidence of it, no obvious signs. >> water lines are fairly decently marked but gas lines, no. >> reporter: those pipelines are a subterranean oil and gas superhighway crisscrossing the nation, 2.5 million miles of pipeline, enough to wrap around the earth 100 times. much of that infrastructure is at least 40 years old and in some cases in decay. >> it's kind of a wake-up call for all of us.

the vast majority of these large high-pressure transmission pipelines are never required to be inspected. >> reporter: that's because only pipelines near natural resources or population centers are subject to mandatory inspection and only 7% of those major lines run anywhere near a neighborhood. utility companies know where pipelines are buried, but residents might not. barbara pinto, abc news, chicago. >> and one tip for homeowners -- natural gas leaks smell like rotten eggs. and if you want to learn about other clues, head to abcnews.com/worldnews. and we move on now to the election just 50 days away shaping up as a giant showdown about jobs, the middle class and taxes. and not only is the president taking on the republicans, going head to head, the republicans and democrats are now fighting among themselves. jake tapper is at the white house. >> reporter: the president met with middle class voters in fairfax, virginia, today. >> i'm a massage therapist.

>> i've got a crick in my neck. >> i bet you do. >> reporter: and there he continued to push the idea that republicans have a stranglehold on a middle class tax cut and are holding it hostage until it's extended to wealthier americans as well. >> because wages and incomes had flat-lined for middle class families, they should definitely get an extension of the tax cuts that were instituted in 2001, 2003. >> reporter: over the weekend, house republican leader john boehner essentially gave in, saying he'd go along with continuing those bush tax cuts for middle-class voters, even if the cuts for higher wage earners are allowed to expire. >> if the only option i have is to vote for some of those tax reductions, i'll vote for them. >> reporter: but today, leader boehner realized he was out on a limb all by himself. senate republican leader mitch mcconnell said senate republicans are united against any tax increase. >> only in washington could someone propose a tax hike as an

antidote to a recession and this is no small tax hike. >> reporter: and it's not just republicans squabbling. some democrats are breaking from the president and want to extend all the tax cuts. >> given the fragility of the economy, all of the bush tax cuts should be extended temporarily. we need to remember that the top 5% income bracket in america account for 30% of all consumer spending. >> reporter: according to the nonpartisan congressional budget office, if all the bush tax cuts are extended, along with some other provisions, economic growth in the next year could almost double. long term, however, economists say since none of the tax cuts are paid for, they're all deficit spending and unsustainable. and, diane, after all this back and forth, you might wonder just where does this all leave us. basically where we were last week, headed to a standoff with all wage earners taxes scheduled to go up on january 1st, diane. >> well, jake, as you know, tomorrow is the last big primary day, as we head towards the november elections.

voters going to the polls in seven states and washington, d.c. so we thought we'd look at the impact of the tea party so far and what one race tomorrow will tell us about the movement in days to come. john karl now on the personalities garnishing all the attention. ♪ god bless america >> reporter: it would be the tea party movement's biggest upset yet. >> there is a tidal wave coming to delaware. >> reporter: christine o'donnell is an unlikely tea party hero, a marketing consultant who has twice run for senate and twice been trounced. >> hi, this is governor sarah palin. vote for christine o'donnell for u.s. senate. >> reporter: but now she's got an endorsement from sarah palin and she is driving the republican establishment nuts. the establishment candidate is congressman mike castle. gop leaders say if castle wins the nomination, they win joe biden's old senate seat. if not -- >> she were by some miracle to be our nominee that we would lose this seat and lose it by

unprecedented numbers. >> reporter: but castle is a pro-abortion rights, pro-gun control moderate. >> the republican party has lost its way. they get behind candidates like my opponent who don't even support the republican platform, who continue to support the democrats agenda, lock, step and barrel. >> reporter: whatever happens here in delaware, tea party senate candidates have already toppled the choices of the republican establishment in at least six states this year. castle watched as tea partier joe miller toppled alaska senator lisa murkowski. >> she called me, you know, several days after she went down and said, you know, these people will come hard, you know, just be very careful. >> reporter: did she give you advice on -- >> yes, just general advice, be careful, prepare yourself and go for it. >> reporter: he's certainly not holding back. even attacking o'donnell for problems with her personal finances. >> -- using campaign funds to pay her own rent --

>> reporter: clearly, this unlikely tea partier has the establishment worried. jonathan karl, abc news, dover, delaware. and up next, weather watch -- hurricane forecasters have their eye on a mega storm in the atlantic tonight. the biggest in three years. igor is already a category 4 hurricane with winds of 150 miles an hour and headed towards a category 5. it's more than 800 miles across, bigger than texas. tonight it doesn't look as if igor will threaten the east coast but hurricanes change course, so everyone is watching. and a troubling discovery tonight about the story that consumed us over the spring and summer, the oil spill in the gulf. almost a month ago, the u.s. government said 75% of the giant spill had simply disappeared. but our matt gutman is in touch with scientists who are on the ocean tonight probing the ocean floor and finding oil. >> reporter: it's a mystery that has bedeviled scientists and the government. over 180 million gallons of crude spilled but much of it

seemed to vanish. so where did it go? one group of scientists now think they have the answer. down. >> the oil is not gone. it's in places where nobody has looked for it. a lot of it is on the bottom. >> reporter: over the past couple of weeks, joye and other researchers have pulled up cones of sediment from the seafloor, finding a layer of sludge over 2 inches thick and extending up to 70 miles out from the wellhead. we reached joye via satellite phone, just a few miles away from the initial spill zone. what is the potential fallout for wildlife, for marine life? >> i have yet to see a living shrimp, a living worm, nothing. these guys basically just got suffocated by a flood of this stuff. >> reporter: joye cautions these findings are preliminary. but it's enough of a threat to larger fish and perhaps humans that she feels compelled to talk about it. the last time she felt so compelled she and a team of scientists had just discovered oil plumes lurking in the gulf. federal scientists immediately

demanded they stop talking about it but later acknowledged the plumes exist. do you feel you've been bullied? >> i think that's kind of fair to say. >> reporter: and when joye and others challenged the government's recent assertion that 75% of the oil was gone, the administration tried to discredit them. this time, federal scientists are listening. abc news has learned the government will this week launch a massive new initiative to hunt for the oil still in the water and in the sediment and that they've enlisted dozens of scientists, including joye, for help. matt gutman, abc news. and we have some welcome news from the fbi tonight -- crime is down again in america. violent crime nationwide dropped more than 5% last year. and property crime was down almost as much, despite the bad economy. one reason -- police in major cities using computers to zero in on crime hot spots and focusing their resources where they're needed the most. still ahead now on "world news" -- kids suffering brain injuries from basketball?

why are the numbers soaring, especially among girls? and the medal of honor winner -- what he did for a friend and fellow soldier. our martha raddatz with the first interview. [ man ] this is bailey's favorite time of day. mine too. i'm chef michael, and i love to delight bailey's senses. don't i? [ barks ] because i think food speaks a language of love. that's what inspired me to rethink dry dog food. [ female announcer ] chef michael's canine creations. [ chef michael ] mmm. tender shredded pieces made with real meat... and crunchy garnishes to enhance the mealtime experience. yes, bailey-- just for you. [ barks ] [ female announcer ] chef inspired, dog desired. chef michael's canine creations. desperate for nighttime heartburn relief? for many, nexium helps relieve heartburn symptoms caused by acid reflux disease. and for the majority of patients with prescription coverage for nexium,

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some sobering news tonight about the most popular sport for american children and teens, basketball. when you think of the hazards of basketball, you think of

sprained ankles or sprained fingers, but a journal called "pediatrics" has a new study which says the number of teenagers and adolescents suffering traumatic brain injuries from basketball is soaring. here's sharyn alfonsi. reporter: that's niki popyer, number 23. a star on the court who thought basketball would be her ticket to college. but today those dreams have been benched. do you play basketball at all anymore? >> no, i'm not allowed to play anymore. >> reporter: multiple concussions have left niki unable to finish tests, homework -- even a full day of school. it started in the 7th grade when niki hit her head on the gym floor. by age 14, she had suffered seven concussions playing basketball. how do you get, you know, seven concussions on the court? >> i mean, i guess as an athlete i just wanted to win and i would do anything in my power to make that happen. >> reporter: today, just touching her head can cause her to have another concussion. >> i can't go to the movies or

ride a train -- anywhere i might potentially get hit. >> reporter: and just standing up right now? >> i'm going to have such a bad headache later. >> reporter: just search youtube and you can see why the number of young people suffering head injuries while playing basketball is on the rise. researchers say traumatic brain injuries playing basketball, spiked 70% over 10 years. more kids now play basketball than any other sport. and e.r.s report basketball now accounts for more head injuries than even football. >> as an adolescent is growing, they are learning new things. they're developing synapses and wiring of the brain and so anything that interrupts that can have a devastating outcome -- a devastating result. >> there's so many parents and players that would say, oh, stop, you can go back in, i mean, it's nothing, it's just a hit on the head, but they don't know how i'm feeling inside. >> so sharyn is here now. tell me more about why girls, why the rate is escalating among them. >> well, the experts think it's

because girls are playing more aggressively than ever before but they also think some of the guys aren't reporting their injuries and they're playing on, playing through it, and that's part of the problem here. >> all right. well, this is stunning to me, basketball, didn't know that. thank you, sharyn alfonsi. and still ahead -- oprah, a big beginning to the final year? her audience surprised with an amazing gift. when you have osteoporosis, like me, it helps to eat calcium-rich foods like yogurt, spinach, and cheese. but calcium, vitamin d and exercise may not be enough to keep your bones strong. so ask your doctor about once-monthly boniva.

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have come ashore because the sea ice they normally rest on has been melting. the ice has melted twice before in very recent times, 2007 and again last year. and we knew it would be big. the suspense is now over. how would oprah winfrey kick off the final season of her show today? she's given her audience gifts before, but listen -- >> maybe i should take all of you with me to the other side of the world! [ cheers and applause ] we're going to australia! [ cheers and applause ] we are going to australia! [ cheers and applause ] >> off to australia. and that's john travolta who is a pilot and has flown with qantas. oprah and her audience 300-strong will make the eight-day trip in december. and the passing of someone who uttered the most famous line from one of the most famous

science fiction movies ever, "invasion of the body snatchers." >> they're after you! they're after all of us! our wives, our children, everyone! they're here already! you are next! you're next! >> kevin mccarthy was a respected actor who also starred in the stage and movie versions of "death of a salesman" which earned him an oscar nomination. kevin mccarthy died this weekend. he was 96. still ahead -- the new medal of honor winner, 22 years old, showing what courage looks like, his first interview. looks like, his fi rst interview. i know who works differently than many other allergy medications. hoo? omnaris. [ men ] omnaris -- to the nose! [ man ] did you know nasal symptoms like congestion can be caused by allergic inflammation? omnaris relieves your symptoms by fighting inflammation. side effects may include headache, nosebleed, and sore throat. [ inhales deeply ] i told my allergy symptoms to take a hike. omnaris. ask your doctor. battling nasal allergy symptoms? omnaris combats the cause.

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[ male announcer ] we bet you'll love zyrtec®, too -- or it's free. [ vonetta ] it is countdown to marshmallow time. [ woman laughs ] finally, you may remember, last week, we told you that the nation's highest military award, the medal of honor, will be giving to a living serviceman for the first time since the vietnam war, for an extraordinary act of heroism in a region of afghanistan known as the valley of death. tonight in his first interview, he tells martha raddatz what happens the day his world stood still. >> reporter: staff sergeant salvatore giunta was waiting at his army post in italy with his wife, jennifer, when the call come from washington. >> my heart started racing

pretty fast at that time, and then when he said "president barack obama," it was really pounding. >> reporter: the honor of this award is mixed with the reality that the day of the battle was the saddest day of sergeant giunta's life. how often do you remember that time, that day? >> i think about it multiple times a day. i think about it every day. [ gunfire ] >> reporter: he was just 22 years old at the time, during this battle, which abc news cameras captured. it was a fight so intense, an ambush so sudden, that soldiers were lying wounded within seconds. among them, giunta's closest friend, sergeant josh brennan -- shot multiple times and cut off from the other soldiers. >> to tell the story about that day hurts me. >> reporter: staff sergeant brett perry, back in afghanistan

for a second tour, was with giunta on that frigid mountain during the battle. >> i can't even begin to describe how intense it was. the most intense whizzes i've ever heard from bullets just going right over us. >> reporter: and that is when sal giunta went far beyond the call of duty. with two taliban fighters now dragging his friend josh brennan away, giunta charged right into the ambush, killing one of the taliban fighters and chasing the other away. giunta pulled his friend brennan to safety. >> sergeant giunta was just right there with him, just holding his hand. >> reporter: despite giunta's efforts, it was too late to save josh brennan. >> i'll always think of him fondly. i'll always think of him the way he was and someone who gave everything for his country. >> they'll say he was just doing his job but the reality is there's very few people in the world that would have done what he did. >> reporter: do you know what

the award says, above and beyond the call of duty? >> yes. everyone who has gone above and beyond the call of duty received the medal of honor, i think everyone i stand with would have the medal of honor. >> reporter: martha raddatz, abc news, italy. >> above and beyond. and you can see more of martha's interview later on "nightline" tonight. we hope you had a great weekend. we hope you'll join us right back here tomorrow night. tonight from san bruno, return of more residents to burned out neighborhoods and frustration of those who can't get in. >> we have... possibly several blocks on fire at this time. >> and the chaos at ground zero. the faulty information that confounded the first responder autos what are the chances of

this happening your neighborhood? tonight we'll identify two bay area pipe lines that are most at risk. >> if you speak up like i did, they try to shut you up. >> the man who blew the whistle on pipeline safety practices at pg&e. >> good evening, dozens of residents being allowed to return home tonight in the san bruno neighborhood destroyed by fire last week. >> many are frustrated by the fact those its taken this long. >> the people whose homes were destroyed in the inferno were bused in to see damage for the first time late today. pg&e established a $100 kblinl fund to help homeowners and the city rebuild. the pipe blown out of the ground is now being shipped to washington, d.c. for analysis by the national transportation safety board. it conduct aid briefing less than an hour ago. >> the question is have w