The Inter-American Development Bank has approved four technical assistance grants to South American countries for a total of $9.8 million.

The largest grant, for $7.1 million, will help pay for construction materials for 4,500 low-income families in El Salvador affected by the October 1986 earthquake. The earthquake destroyed or seriously damaged about 56,000 houses. IDBs grant also is paying builders to teach people carpentry.

The bank granted $27,710 to help encourage joint ventures between private companies in Argentina, Colombia, Ecuador, Venezuela and West Germany. West Germany's Ministry of Economic Development is financing the project. Initially, participants will study industrial programs in each country and choose executives to meet in Hamburg and Hanover, West Germany, next April. The next stage of the project will be decided in April.

Suriname received the last two grants, one for $1.2 million and the other for more than $1 million. The first grant is for a study of Suriname's drainage and irrigation system to determine how to rehabilitate the country's water system. In the second project, consultants will study the final designs and bidding documents for an electric plant to be constructed in Tambaredjo. The project also includes a study of the Suriname Power Project and the utility rates it charges.