Cooperative Extension Service offices are located all over the metropolitan area. Volunteers are on hand to help callers with food-preserving questions. In addition, all of these offices will be holding preservation workshops during the summer. Call your local offices to find out when and where: DISTRICT OF COLUMBIA

Administrative Offices: 929 E St. NW, 20004. Phone: 727-2004.

1351 Nicholson St. NW, 20011. Phone: 282-7410.

1725 Lincoln Road NE, 20002. Phone: 576-7419 and 576-7415.

11th & Harvard Streets NW (send mail to 929 E St. NW, 20004). Phone: 727-6880. MARYLAND

Frederick: 520 N. Market St., Frederick 21701. Phone: (301) 694-1599.

Howard County: 8306 Forrest St., Ellicott City 21043. Phone: (301) 992-2030.

Prince George's County: 15209 Marlboro Pike, Upper Marlboro 20772. Phone: 952-3116.

Montgomery County: 600 S. Frederick, Gaithersburg 20877. Phone: 948-6744.

Baltimore County: Agriculture Building, 9811 Van Buren Lane, Cockeysville 21030. Phone: (301) 666-0445. VIRGINIA (Preservation Hotline for Northern Virginia between 1 and 4:30 p.m., Monday through Friday: 691-3428)

Alexandria: 901 Wythe St., Alexandria 22314-1884. Phone: 838-4333.

Arlington: 855 N. Edison St., Arlington 22205. Phone: 558-2475.

Fairfax County: 3945 Chain Bridge Road, Fairfax 22030. Phone: 691-3350.

Loudoun County: 137-B S. Catoctin Circle, Leesburg 22075. Phone: 471-6050 Ext. 373.

Prince William County: 8805 Sudley Road, Suite 200, Manassas 22110-4796. Phone: (703) 361-8989.