The Napa Valley vineyard's owner, Rene di Rosa, said Jos. E. Seagram & Sons has signed a letter of intent to purchase 250 acres of the 460-acre Carneros property. Di Rosa did not disclose the value of the sale. Di Rosa plans to convert the balance of the property into an "art park." The 250 acres, planted in Chardonnay and Pinot noir grapes, will become the southernmost estate of Sterling Vineyards, which is a part of the wine production division of Seagram. Since di Rosa established Winery Lake in 1960, the Carneros appellation Chardonnay and Pinot noir grapes have been prized by area wineries. Terms of the sale were not disclosed.