Officials from Utah Power & Light Co. and PacifiCorp expect their merger to officially take effect Jan. 9, as both companies spend the rest of this week putting together final details of the $2 billion deal.

On Tuesday, the 10-day pricing period ended to determine what value UP&L shareholders will get for their stock. PacifiCorp's stock yielded an average price $35.713 per share during the period. At that price, UP&L shareholders will receive .909 of PacifiCorp for each share of UP&L."We are pleased to see our stock did maintain it's value" during the pricing period, PacifiCorp spokeswoman Dolores Chenoweth said.

Under the stock swap agreement, a UP&L stockholder with 100 shares, which closed Tuesday at $31.625 a share, will receive 90 shares of PacifiCorp, worth $35.71 a share, and cash payment for the fractional shares.

UP&L preferred shareholders will receive PacifiCorp preferred on a share-for-share basis.

Shareholders will receive information and instructions sometime next week from First National Bank of Chicago, the companies' exchange agent, on how to covert the stock, officials said.

To facilitate the stock swap, valued at $1.9 billion, PacifiCorp will issue about 53.5 million new common shares in exchange for outstanding UP&L shares. The new shares will bring PacifiCorp's total common stock outstanding to 123.2 million shares, a spokesman said.

With the additional shares and UP&L earnings being less than PacifiCorp, earnings per share for PacifiCorp will become diluted as a result of the merger.

But, PacifiCorp will maintain its annualized dividend of $2.64 a share, Chenoweth said, compared to UP&L's annual dividend of $2.32.

Because UP&L shareholders will not receive a full share of PacifiCorp, they will not realize the full difference between the dividends. For example, the annual dividends for a UP&L stockholder with 100 shares will increase from $232 to $237.60, not to $264, because the 100 shares of UP&L stock will be converted to 90 shares of PacifiCorp.

Both utilities plan to finish up legal details of the merger this week and sign merger papers over the weekend. An official announcement that the merger has taken effect is scheduled for Jan. 9, after government officials in Oregon, Utah and Maine have received the papers indicating the change, a PacifiCorp spokesman said.

Under the agreement, UP&L will become a division of PacifiCorp - a diversified utility holding company based in Portland, Ore., and parent of Pacific Power & Light. Both utilities claim annual savings of up to $150 million by merging the operations of PP&L and UP&L, enabling promised rates decreases of at least 5 percent for UP&L's customers within five years of the merger.

Two percent of that promised rate reduction will take place by March 1989, the utilities say.

It has taken more than 16 months for the companies to clear regulatory hurdles before going ahead with the merger. Seven state regulatory agencies, including Utah, and the Federal Energy Regulatory Commission have given their blessing to the marriage. But the FERC has granted a request for rehearing on its order to consider numerous protests against federal conditions to the merger.

PacifiCorp attorney George Galloway said the order granting rehearing doesn't affect the FERC's approval of the merger.