Slide Number 12 in the appendix demonstrates this activity and effect.
In fact, maybe the most important slide we have ever published is Slide Number 12.
It is not cyclical and is quite steady when Olin does not push excess volume and chase the poor quality side of the ECU down across an inflection point on Slide Number 12 into an over-supplied swamped of poor pricing.
Now, turning your attention to Slide Number 3, Olin's quarterly ECU profit contribution index chart, even though the global Chlor Alkali market configuration is in the poorest state for Olin, in other words when strong, back integrated PVC production, which Olin does not directly participate in, pushes out lots of co-produce caustic into a weak caustic demand environment, really the emphasis being on the weak caustic demand point here, we still sequentially lifted our ECU PCI by lifting margins across chlorine, EDC and virtually every chlorine derivative while simultaneously not allowing Olin caustic to decline in price as much as industry indices would have anticipated.
And speaking of quality and moving to Slides 4 and 5, Winchester delivered the best quarterly performance in the business's 155-year history with even better quarters expected throughout 2021.
The Olin Winchester team relishes its commitment to support both the U.S. war fighter and the more than 55 million of us who enjoy shooting sports.
So wrapping up my opening comments with Slide Number 6, our first half quarterly average EBITDA should be better than the fourth quarter of 2020 across every business.
Note that we do have a number of turnarounds in the second quarter to contend with and we expect a 10% improvement in the ECU PCI across the first half.
Point number 1, Epoxy will be the star of the show and is expected to surpass our prior quarterly EBITDA record as the team lifts the permanent earnings foundation of that business to match the value of our product offering.
Point number 2, our merchant chlorine net-backs go to a multi-year high, following our fourth quarter activations, which included shifting an additional 30% of our ongoing business away from arbitrary external trade indices.
Point number 3, our broad productivity gains start to show up as our fourth quarter project pipeline grew by 20%.
We start 2021 with 633 active projects.
Please see Slide number 15 in the appendix for some more detail on that.
Point number 4, the early redemption of $120 million of the high cost acquisition bonds this month was funded a 100% with cash from operations, as was the additional $100 million of bonds repaid last October.
Through a combination of improved adjusted EBITDA, disciplined capital spending and debt reduction, we expect our net debt to adjusted EBITDA ratio to improve to roughly three times within the next 12 months.
So looking out just a bit beyond 2021 we have the team, the skill, the operating model and the assets we need to achieve at least $1.5 billion in EBITDA.
Additionally, we have adjusted down our forward annual capital spend requirements to around $200 million, reflecting a better match of our physical plant assets to our model.
This adjustment in turn enhances our levered free cash flow and that cash flow inflection point should be clearly evident in 2021.
At the same time we rinked $1.5 billion in EBITDA, global ECU supply demand fundamentals are likely to be improved and Olin will expand our strategy to incorporate fixed asset light structural moves to take us to the next higher EBITDA level, as more molecules move through our sphere of influence.
We will look forward to speaking with you in the future about the next EBITDA tranche above $1.5 billion and those supporting activities.

Summary:
This adjustment in turn enhances our levered free cash flow and that cash flow inflection point should be clearly evident in 2021.