Waltham (Mass.) Contributory Retirement System is looking to combine two $12 million active domestic large-cap portfolios, one value and one growth, into a single core strategy portfolio in an effort to save money. SSgA has run the value and growth portfolios for the $156 million pension plan and can rebid, said Joseph Juppe, board administrator. Kevin Leonard, the $156 million pension plans consultant with Segal Advisors, was not available at press time. Fund officials expect to select a core manager by June 30.