Hello everyone,

The big story of the day is in Ottawa, where things have the potential to get quite heated.

Environmentalists are staging a massive protest on Parliament Hill against a proposed pipeline that would carry crude oil from the Alberta oils sands to the U.S. Gulf Coast – passing through six states.

The protests come as the U.S. State Department is expected to give a final federal decision sometime this fall on whether the proposed pipeline is in its national interest.

Meanwhile, the $7-billion Keystone XL project has triggered strong opposition in the U.S., where protesters have staged sit-ins in front of White House all month.

Celebrities have been supporting the cause. I'm sure you've heard about Daryl Hannah's arrest, and there was this YouTube call-to-action by Oscar-nominated actor Mark Ruffalo.

Our Ottawa reporter Daniele Hamamdjian (@dhamamdjian) is at the scene this morning. She tweeted this photo along with news that protesters are beginning to cross security lines. UPDATE: just after noon ET, at least 15 people have been arrested.

Here's another photo from the scene of what appears to be snipers on top of the Senate building:

So what's this all about? For those of you new to this issue, let's try to break it down.

Here's what supporters of pipeline are saying:

• The Canadian government and TransCanada Pipeline promise 20,000 jobs in construction -- and thousands more in oil refinery jobs once the oil gets to Texas. And this in a time of economic downturn.
• It could generate $2.3 trillion in economic activity over the next 25 years.
• It will provide energy security within North America.
• It will send crude that Canada doesn't have the capacity to refine to Texas refineries, who are looking for it.
• It will be the safest pipeline ever built.

Here's what protesters of the pipeline are saying:

• Bitumen oil is among the dirtiest on the planet.
• It will threaten water supplies. (the pipeline would be routed over Nebraska's Ogallala aquifer – which supplies water for drinking and agricultural irrigation to parts of 8 U.S. states).
• Number of jobs promised are likely overstated and their long-term future is questionable.
• No matter how safe you try to make a pipeline, they still leak.

Natural Resources Minister Joe Oliver (you can watch his appearance on Sunday's Question Period here) says Keystone is part of a larger objective -- of turning Canada into a responsible energy superpower. We have excess capacity, and the U.S. has excess demand, he adds.

Your comments on this heated issue are starting to roll in. Some of you suggest the pipeline would leave a black mark on our environmental record, including Chris in Alberta who says:

"We've already seen what happens when this crude is spilled. People have a right and a reason to be concerned and it doesn't matter if they arrive by bicycle or jet plane -- that red herring is irrelevant to the reality of environmental destruction caused by the TARsands boom frenzy."

But so far today, many of the comments we've seen seem to focus on whether the pipeline is good or bad for the economy.

Leroy_Jethro_Gibbs asks on our website whether protesters are aware of the potential financial cost of their stance?

"Are these people aware of the risk they pose to medicare, education, and other social programs with their stance? These things require massive amounts of money that can only be obtained through trade with the US -- oil just happens to be the most remunerative. So, if you love Canada and its social safety net, you must support the Keystone XL pipeline."

Jimminy Cricket asks why we need to send crude oil to refineries in the US only to have them sell the finished product back to Canadians "at an over-inflated price." "Refineries have closed in Canada over the past 10 years and lots of jobs have been lost. So we're sacrificing good paying jobs in exchange for overpriced gasoline and diesel. Thanks a lot," he writes.

Camwest had an interesting response: "We are not making any refineries because we have no people to build them. The labour force in Western Canada is tapped dry. Our friends in Newfoundland have jobs back home now. There are rigs sitting because there are no workers. Everyone is being stretched to the limit."

Politicians are weighing in as well on Twitter, including Green Party leader @ElizabethMay who says: Today, protests are planned against oil sands expansion & Keystone pipeline. I support peaceful, non-violent acts of conscience.#cdnpoli

@pbsolar asks whether this is a "#Pipeline to prosperity or channel to catastrophe?"

My questions today for you is: Do you feel sufficiently informed about the oil sands and the reason for the protests?

And do you think it's tougher to get an environmental point across when we're going through tough economic times?

Please let me know.

Lisa