A delighted Bishop John T. Walker announced yesterday that the Washington Cathedral this week reached its goal of raising $16 million to wipe out earlier construction debts, complete the Pilgrim Gallery above the west facade and establish an endowment to pay for maintenance.

The successful three-year fundraising effort, Walker said, "has allowed us to finish the Pilgrim Observation Gallery by the 75th anniversary" of the cathedral, celebrated Wednesday with the formal dedication of the gallery, "and at a cost below our most optimistic projections."

In addition, he said, funds are in hand to begin work next spring on the towers of St. Peter and St. Paul, which will complete the west facade.

A crash building program in 1976 to complete key element of the cathedral in time for a series of Bicentennial celebrations left the institution nearly $11 million in debt. In 1977, the year Walker was formally installed as Episcopal bishop of Washington, all construction was put on a strictly pay-as-you-go basis; canons and choirboys were let go; thermostats were lowered, and other cost-cutting measures instituted.

Two years later the campaign for $16 million (actually a campaign for $15.5 million plus $500,000 for campaign expenses) was launched.

Washington Cathedral, which is properly known as the Cathedral of Sts. Peter and Paul, is unique in the Episcopal Church in this country since it serves as the ecclesiastical seat of the diocesan bishop and of the presiding bishop of the Episocopal Church in the United States. While it functions as an integral part of the diocese here, it is controlled by its own governing board, which is responsible for its funding.

In the financial campaign just ended, $12 million has been received, and pledges are on hand for just over $4 million. Canon Charles Perry said the pledge income will "eliminate the remaining debt by 1985, as planned, and cover interest accruing during the interim period as well."

Today the cathedral is holding an open house from 10 a.m. to 4 p.m., featuring bagpipe, organ and choral music, an antique carrousel, and demonstrations by calligraphers, flower arrangers, stained-glass workers and other artisans. At 4 p.m., the West Portal Tympanum, "The Creation," an 18-foot stone carving by Washington sculptor Frederick E. Hart and master carver Vincent Palumbo, will be dedicated.

At 11 a.m. tomorrow, a four-paneled Psalms Window, depicting psalms of supplication, lamentation, joy and praise, will be dedicated in honor of the Very Rev. Francis B. Sayre, dean emeritus, who will be guest preacher.