Truncer's first full-time position was with the NPS's Northeast region office and it resulted in him concluding that he did not want to work in a large agency. After completing a tour of active duty in Europe with the New Jersey Air National Guard, which was precipitated by the Berlin crisis, Truncer accepted a position with New Jersey state parks working on the state's "green acres" program which was created in 1961 after New Jersey voters authorized $60 million for park and open space acquisition. The funds were used both for state level acquisitions and for 50% grants to local jurisdictions to encourage them to invest in parks. This was the first such matching grants program for parks in the country.
In 1964 Truncer was hired as principal park planner by the Monmouth County Planning Board in New Jersey and in that position he was responsible for organizing and preparing the first Monmouth County park system budget. The park system at that time was comprised of three parks totaling approximately 300 acres. He was appointed as the county's first parks and recreation director in 1966 with an operating budget of $138,000, a capital budget of $265,000 and a total staff of twelve. He reported to the Board of Recreation Commissioners which was a three person policy making board. In 1974, his title was changed to secretary-director to the Board of Recreation Commissioners.
Truncer invested his career in the development of the Monmouth County Park system. The policy making board to whom Truncer reported was expanded to nine members. In 2004, the operating budget was $17.9 million supported by an additional $7.1 million in trust income; the capital budget was $15.6 million; total revenues exceeded $12.7 million and the department had 350 full-time, 7 part-time, and 353 seasonal and hourly employees. Thus Monmouth County has grown into one of the nation's most eminent county park systems with 36 park areas (including 6 golf courses) totaling over 13,300 acres with another 750 acres in easements, and an annual visitation exceeding 4 million. The county is in the New York-New Jersey metropolitan region and has been recognized as one of the nation's best places to live, and the park system under Truncer's leadership has been a contributing element to that distinction.
In 1987, the county's voters approved a property tax dedicated to an open space trust fund, which provided $4 million per year for park acquisition and development. This was the first dedicated county open space fund established in New Jersey. In 1996, the voters increased the annual amount from $4 million to $10 million, and again in 2002 Monmouth County voters increased the amount from $10 million to $16 million. This tax provides $12 million each year to acquire land for open space (of the remaining $4 million, $2 million goes to county park improvements and $2 million to municipalities as matching grants to purchase open space or make park improvements).
The system that was developed under Truncer's leadership is comprehensive, extending beyond creating park and open space opportunities. It includes:
Truncer held many leadership positions in professional associations including being president of the New Jersey Recreation and Park Association and the Academy of Park and Recreation Administration, and he was a leader in the movement to establish an accreditation program for agencies in this field. After helping establish accreditation, he subjected his own agency to the rigorous process and in 1994 was the first agency in the field to become accredited and subsequently was the first to be reaccredited in 2004.
Truncer assisted in launching two nonprofit 501(c)(3) organizations which support the park system; Monmouth Conservation Foundation, (1977), a land trust whose assets were over $7 million in 2003; and Friends of the Parks (1993), a support organization that has raised since its inception over $1.4 million. Through a cooperative agreement with Special People United to Ride (SPUR) (1981), a 501(c)(3) organization that supports a riding program for people with disabilities was established in the park system that has raised over $1 million for the program. Truncer has also championed collaborations with other nonprofits and other public agencies to provide expanded public open space, parks and recreation programs and facilities in Monmouth County.