We are a leading specialty contractor operating mainly throughout the United States and across a range of industries. Our core activities are the building, installation, maintenance and upgrade of utility and communications infrastructure, including but not limited to: electrical utility transmission and distribution, wind farm, solar farm and other renewable energy, natural gas and petroleum pipeline infrastructure, wireless, wireline and satellite communications and water and sewer systems. Our primary customers are in the following industries: utilities (including wind farms, solar farms and other renewable energy, natural gas gathering systems and pipeline infrastructure), communications (including telephony, satellite television and cable television) and government (including water and sewer, utilities and communications work on military bases).
We, or our predecessor companies, have been in business for over 75 years. We offer our services primarily under the MasTec service mark and operate through a network of approximately 200 locations and approximately 8,600 employees as of December 31, 2009. We have consistently ranked among the top specialty contractors by Engineering News-Record over the past five years.
We serve a diversified domestic customer base including DIRECTV®, AT&T, Enbridge, Verizon, Duke Energy, Iberdrola Renewables, Great River Energy, Florida Power & Light, Oneok and Dominion Virginia Power. For the years ended December 31, 2009, 2008 and 2007, approximately 72%, 72% and 77% of our revenues were from our ten largest customers, respectively. We have longstanding relationships with many customers and often provide services under multi-year master service agreements and other service agreements.
We have continued our diversification and expansion strategy through several recent acquisitions which have expanded our service offerings to customers. During 2007 and 2008, we acquired the remaining ownership interest in GlobeTec Construction, LLC. GlobeTec is involved in the construction and maintenance of water and sewer pipelines and projects. In October 2007, we acquired Three Phase Line Construction, Inc., which is involved in the construction and maintenance of transmission and distribution utility systems, substation and storm restoration in several northern states and has a largely unionized workforce, which is required for certain projects. In December 2007, we acquired certain assets of Power Partners, LLC, an electrical utility contractor specializing in wind farm electrical system design and construction. In May 2008, we acquired Pumpco, Inc., which we refer to as Pumpco, a mid-stream natural gas pipeline construction company. In July 2008, we acquired certain assets of Nsoro, LLC, which specializes in wireless network design, construction, upgrade and maintenance. In December 2008, we acquired Wanzek Construction, Inc., which we refer to as Wanzek, a construction company focusing on wind farm, heavy civil and industrial and infrastructure construction. In November 2009, we acquired Precision Pipeline, LLC, which we refer to as Precision, a large diameter natural gas, crude oil and refined products transmission pipeline construction and infrastructure services provider, which has a largely unionized workforce.
In June 2009, we completed an underwritten public offering for $115 million of 4% senior convertible notes, as well as a public secondary offering of 5.175 million shares of common stock by certain selling shareholders. The 4% senior convertible notes are convertible into shares of our common stock at a conversion price of approximately $15.76 per share of common stock, and are subject to customary anti-dilution adjustment terms for these types of notes. The proceeds from the 4% senior convertible notes were used to repay the $55 million of 8% convertible notes, convertible at $12.00 per share, issued in connection with our 2008 acquisition of Wanzek, and to pay off the outstanding balance on our credit facility of approximately $20 million. The remaining net proceeds were used for working capital, acquisitions and for general corporate purposes.
Concurrent with the issuance of the 4% senior convertible notes, Jon Wanzek, CEO of Wanzek and his affiliates sold 5.175 million shares of MasTec common stock in an underwritten registered public offering. Mr. Wanzek and his affiliates received 7.5 million MasTec shares in connection with our 2008 acquisition of Wanzek. Mr. Wanzek continues to serve as President of Wanzek under an employment contract. We did not receive any proceeds from the sale of the shares of common stock by the selling shareholders.
In November 2009, we purchased all of the issued and outstanding membership interests of Precision Pipeline, LLC for approximately $132 million in cash, the assumption of $34 million of Precision’s debt and a five-year earn-out equal to 40% of Precision’s EBITDA (as defined in the purchase agreement) for the last two months of 2009 and 30% of Precision’s annualized EBITDA in excess of $35 million for the remainder of the earn-out period, payable at our option in cash or shares of our common stock, or a combination thereof. Concurrent with the Precision acquisition, we issued $100 million of 4.25% senior convertible notes. The 4.25% senior convertible notes are convertible into shares of our common stock at a conversion price of approximately $15.48 per share of common stock, and are subject to customary anti-dilution adjustment terms for these types of notes. The net proceeds from the offering were used to fund the acquisition of Precision and for general corporate purposes.
Precision, based in Eau Claire, Wisconsin, is a leading energy infrastructure services provider, specializing in the construction and maintenance of large diameter pipelines. Precision’s experience in the long-haul, interstate pipeline industry complements our existing energy infrastructure service offerings, which include natural gas gathering systems, processing plants and compression stations and mid-stream pipelines. We believe that our acquisition of Precision enhances our end-to-end design and construction capabilities within the energy industry. With the acquisition of Precision, we become one of the leading pipeline contractors in the country, capable of providing a full array of construction services to oil and gas producers, as well as mid-stream and interstate pipeline operators.