We expect the call to last about 60 minutes.
Revenue for the quarter was $1.963 billion.
Adjusted EBITDA was $230 million, adjusted earnings per share was $1.30.
And backlog at quarter end was $9.2 billion, a sequential increase of nearly $1.4 billion.
Our team member count increased year-over-year from 18,000 to 26,500 team members at quarter end and was up sequentially by nearly 6,000 team members.
Considering the challenges in the oil and gas industries, we led our path to achieving annual revenue target of $10 billion, with double-digit margins.
Our full year guidance that we provided today reflects continued diversification, as we expect our non-Oil and Gas business to grow over 20% in revenue and over 30% in EBITDA in 2021, with significant acceleration in the second half of 2021.
Our Communications revenue for the quarter was $630 million and margins improved 290 basis points sequentially.
Comcast revenue was also very strong in the quarter, increasing over 30% from last year's second quarter.
That growth was offset with expected declines in both our Verizon and AT&T business, which were both down over 25%.
Over the last few quarters, we've talked about the opportunities related to the Rural Digital Opportunity Fund or RDOF, which will provide $20 billion of funding over the next 10 years to build and connect gigabit broadband speeds in underserved rural areas and the 5G Fund for Rural America, which will provide up to $9 billion in funding over the next decade to bring 5G wireless broadband connectivity to rural America.
Communications segment backlog, increased sequentially by $489 million, and was driven by bookings across all segment end markets, including wireless, fiber deployments and fulfillment work.
Revenue was $232 million versus $128 million in last year's second quarter.
Revenue was $621 million and margins remained strong.
As a reminder, last year, we forecasted a long-term recurring revenue target of $1.5 billion to $2 billion a year, assuming a continued depressed oil and gas market.
Revenue was $482 million for the second quarter.
Segment backlog at quarter end was at record levels, with a sequential increase of $320 million and a year-to-date increase of $680 million.
In summary, we had strong second quarter results with revenue of approximately $1.96 billion, a 25% increase over last year; adjusted EBITDA of approximately $230 million; and adjusted EBITDA margin rate at 11.7% of revenue.
This represented a 39% increase in adjusted EBITDA dollars and a 120 basis point increase in adjusted EBITDA margin rate over last year's second quarter.
Second quarter backlog of $9.2 billion represented an all-time record high for MasTec.
Importantly, our non-oil and gas segment backlog sequentially increased $1.6 billion with record second quarter backlog in Communications, Clean Energy and infrastructure, and Electrical Transmission.
Our continued focus on working capital management during 2021 has allowed us to easily fund organic working capital needs, while investing approximately $600 million in strategic acquisitions.
As of the end of our second quarter, we maintained a strong balance sheet and capital structure with liquidity approximating $1.2 billion and comfortable leverage metrics.
Second quarter Communications segment operations performed generally in line with our expectations with revenue of $630 million inclusive of expected temporary lower levels of wireless project activity prior to the upcoming construction ramp-up for C-band spectrum awards.
Second quarter Communications segment adjusted EBITDA margin rate was 11.5% of revenue a 290-basis-point improvement sequentially.
Our annual 2021 Communications segment expectation is that revenue will approximate $2.6 billion to $2.7 billion with annual 2021 adjusted EBITDA margin rate improving 90 to 110 basis points over 2020 levels.
Regarding some color on expectations during the second half of 2021, we expect third quarter year-over-year revenue growth in the mid to high single-digit range with fourth quarter year-over-year revenue growth accelerating in the mid to high 20% range.
Second quarter Clean Energy and Infrastructure segment or Clean Energy, revenue was $482 million.
Adjusted EBITDA was approximately $16 million or 3.2% of revenue.
During the second quarter, we estimate the combination of start-up delays and project inefficiencies inclusive of weather, negatively impacted second quarter segment operating margins by 350 basis points to 400 basis points.
As we look forward, we expect improved performance during the second half of 2021 with second half revenue approximating $1.2 billion, slightly over a 40% increase, compared to first half 2021 levels with adjusted EBITDA margins in the range of 7% to 8% of revenue.
And the benefit of exiting two underperforming projects which are approximately 75% complete as of the end of the second quarter.
We are very excited, that Clean Energy's second quarter backlog reached a new all-time record of $1.7 billion.
Our annual 2021 Clean Energy segment expectation is that revenue range between $2 billion to $2.1 billion with annual 2021 adjusted EBITDA margin rate improvement in the 20 basis point to 70 basis point range over the prior year.
Second quarter Oil and Gas segment revenue was $621 million and adjusted EBITDA was $138 million, generally in line with our expectation.
We currently expect annual 2021 Oil and Gas segment revenue will range between $2.4 billion to $2.5 billion with the continued expectation, that annual 2021 adjusted EBITDA margin rate for this segment will be in the high-teens range.
Second quarter Electrical Transmission segment revenue was $233 million and adjusted EBITDA margin rate was 4% of revenue.
Second quarter backlog was $1.3 billion, an approximate $800 million sequential increase.
We completed the acquisition of INTREN, which focuses primarily on electrical distribution mid-quarter and this added approximately $100 million of revenue to this segment during the quarter, as well as most of the segment's sequential backlog growth.
In summary, INTREN's operations performed well, and as expected, during the partial quarter period, while our legacy Electrical Transmission operations were impacted by weather-related project inefficiencies and increased closeout costs on two projects which are over 90% complete, as of the end of the second quarter.
These two projects negatively impacted second quarter Electrical Transmission segment operating results by approximately $8.5 million and 370 basis points.
Looking forward to the balance of 2021, we expect annual 2021 revenue for the Electrical Transmission segment to approximate $950 million to $1 billion and annual 2021 adjusted EBITDA margin rate to approximate 6.5% of revenue.
Relative to the remainder of 2021 expectations, inclusive of INTREN, we anticipate that second half 2021 revenue levels will range in the low $600 million range a year-over-year increase of approximately $350 million.
Second half 2021 adjusted EBITDA margin rate for this segment is expected to approximate 8% of revenue, due to the combination of improved legacy operations as we exit two underperforming projects and the benefit of higher-margin INTREN MSA operations.
Now I will discuss a summary of our top 10 largest customers for the second quarter period, as a percentage of revenue.
Enbridge and AT&T were both 12% of revenue.
AT&T revenue derived from wireless and wireline fiber services totaled approximately 9% and install-to-the-home services, was approximately 3%.
On a combined basis these three separate service offerings, totaled approximately 12% of our total revenue.
NextEra was 8% of revenue comprising services across multiple segments including Clean Energy, Communications and Electrical Transmission.
Equitrans Midstream and Comcast were each 5% of revenue.
T-Mobile, Duke Energy and Energy Transfer were each 3% of revenue and Midstream and Elite were each 2%.
Individual construction projects comprised 68% of our second quarter revenue with master service agreements comprising 32%.
At June 30, 2021, we had a record total backlog of approximately $9.2 billion, up about $1 billion from second quarter last year and up $1.3 billion sequentially from last quarter.
During the second quarter, we easily funded working capital associated with over $120 million in organic revenue growth, as well as approximately $500 million in acquisition activity.
We ended the quarter with $1.2 billion in liquidity and net debt defined as total debt less cash and cash equivalents at $1.3 billion, which equates to a very comfortable 1.4 times leverage metric.
Our year-to-date 2021 cash provided by operating activities was $345 million, $118 million lower than in the first half of 2020.
This performance is impressive as our first half 2021 cash flow includes working capital funding requirements associated with approximately $750 million in higher revenue levels when compared to last year and thus this performance was possible due to our strong working capital management.
We ended the second quarter of 2021 with DSOs at 80 compared to 86 days at year-end 2020 and 90 days for the second quarter last year.
Assuming no second half 2021 acquisition,activity net debt at year-end is expected to approximate $1.1 billion leaving us with ample liquidity and expected book leverage slightly over one time adjusted EBITDA.
We project annual 2021 revenue of $8.1 billion with adjusted EBITDA of $930 million, or 11.5% of revenue and adjusted diluted earnings of $5.45 per share.
Our current view represents a slight decrease in the annual 2021 revenue expectation, primarily due to some project activity slippage to 2022 in communications and clean energy, while reaffirming the annual adjusted EBITDA view of $930 million, and increasing our adjusted diluted earnings per share by $0.05 to $5.45 per share.
We anticipate net cash capex spending in 2021 at approximately $120 million with an additional $160 million to $180 million to be incurred under finance leases.
We expect annual 2021 interest expense levels to approximate $56 million with this level including approximately $600 million in acquisitions funding activity during the first half of 2021.
For modeling purposes, our estimate for 2021 share count continues at 74 million shares.
We expect annual 2021 depreciation expense to approximate 4.2% of revenue inclusive of first half 2021 acquisition activity.
Given these trends, we anticipate that next year annual 2022 depreciation expense as a percentage of revenue will decrease when compared to 2021 levels and approximate 3.5% of revenue.
We expect annual 2021 corporate segment adjusted EBITDA to be a net cost of approximately 1% of overall revenue.
And lastly, we expect that annual 2021 adjusted income tax rate will range between 24% to 25% with the expectation that the third quarter tax rate may be slightly lower than the annual rate.
Our third quarter revenue expectation is $2.3 billion with adjusted EBITDA of $267 million or 11.6% of revenue and earnings guidance at $1.71 per adjusted diluted share.

Summary:
We project annual 2021 revenue of $8.1 billion with adjusted EBITDA of $930 million, or 11.5% of revenue and adjusted diluted earnings of $5.45 per share.
Our current view represents a slight decrease in the annual 2021 revenue expectation, primarily due to some project activity slippage to 2022 in communications and clean energy, while reaffirming the annual adjusted EBITDA view of $930 million, and increasing our adjusted diluted earnings per share by $0.05 to $5.45 per share.
Our third quarter revenue expectation is $2.3 billion with adjusted EBITDA of $267 million or 11.6% of revenue and earnings guidance at $1.71 per adjusted diluted share.