The District of Columbia plans to seek $12 million in federal grants top spur the development of shopping facilities, homes and factories in some of the city's most depressed neighborhoods, Mayor Walter E. Washington announced yesterday.

Among the six proposed projects is a shopping center, expected to cost $19.9 million - mostly in private investment - on the site of the old Hechinger Co. lumberyard and warehouse at the end of the decaying H Street NE corridor.

The announcement came almost 10 years after much of the corridor had been devasted by riots that followed the assassination in1968 of the Rev. Dr. Martin Luther King Jr. The area, once a flourishing retail center, has been in a serious decline.

Under the new proposal, the $12 million would be lent to private sponsors, who would use it for seed money expected to attract more than $52 million in additional investment.

The mayor's announcement said the $12 million in federal funds is not assured. The District of Columbia must compete with several other cities that are expected to seek the $400 million annually that was made a available under a new program of "urban development action grants" authorized last year by Congress.

Spokesman for both the D. C. Department of Housing and Community Development and the U.S. Department of Housing and Urban Development said the proposed projects are of the type Congress apparently had in mind when it approved the program. The filing deadline is April 30.

The D.C. agency's spokesman, Jack Clark, predicted that some - but not all - the city's proposals would be accepted.

The projects on the mayor's list are: The 300,000-square-foot shopping center proposed by hardware store executive John W. Hechinger and land owned by his company at the intersection of H Street, Benning Road and Bladensburg Road NE. Hechinger once proposed the site for the city's stalled convention center, but the mayor rejected the idea, deciding to stick with a downtown site. The program would provide a $4 million loan toward the $19.9 million project.

Construction of a dental clinic at 11th Street and Massachusetts Avenue NW, to be built by EGS, Enterprises for $3.8 million with a $945,000 loan under the federal program.

Quadrupling in size of the Patented Package Corp. factory at 3rd and N Streets NE, which manufacturers gift boxes. The expansion would cost $20 million, with a $5-million loan.

Improvement and expansion of the jartly vacant Stanton Plaza shopping center at Alabama Avenue and Stanton Road SE, in a part of the city where retail facilities are scarce. The project totals $215,000, with a $100,000 loan.

Expansion of the D.C. Research and Development Corp. facility in the 1100 block of 9th Street NW used for training city residents under the Concentrated Employment and Training Act (CETA) program. The project totals $525,000, with a $100,000 loan.

Expansion of a home purchase assistance project operated by the nonprofit D. C. Development Corp. The federal program would provide $2 million to more than 200 families with low or moderate incomes, to be used as down payments on homes. The money would be repaid only when the home is sold in the future. Mortgage loans would be made separately.

If such funds were now available, some apparently could go to the five families on 12th Place NW whose attempt to raise down-payment money has recently been publicized.

The major said the six projects would create about 200 construction jobs and an estimated 1,100 new permanent jobs. The $12 million in loans would stimulate an estimated $52 million total investment, he said.

The proposals for the six projects were sent to the D. C. City Council for approval. Council member Nadine Winter (D-Ward 6), chairman of the Housing and Community Development Committee, scheduled a hearing for 10 a.m. next Thursday.

Sponsors of the various proposals made their submissions, along with others that did not get onto the recommended list, to the D.C. Department of Housing and Community Development in January and February. The department also held a public hearing in January, at which Hechinger disclosed his plan.

The federal money may be allocated only to so-called distressed cities. D.C. officials said there is no doubt Washington could qualify.

Although the mayor sent the proposals to the council as a package, each project will be submitted separately to the U.S. Department of Housing and Urban Development, and must compete against all other proposed projects nationally. There is no funding quota for any given city.

HUD guidelines specify that the proposals will be judged on the basis of the firmness of the private investment, the ability to move fast, the good effect of the project on less affluent residents and on the physical and economic condition of the community.

"If approved by HUD," Mayor Washington said, "these funds . . . would form the basis for a continuing program of city-assisted development, which we have sought for years."

Under the the District's proposal, the grants received from HUD would be lent at 1 to 3 per cent interest rates for 30 to 40 years so that the funds would eventually return to the city treasury for investment in other projects.