Officials of the Hecht Co. and the Pennsylvania Avenue Development Corp. warned this week that new minimum parking requirements proposed for buildings in downtown Washington could have serious adverse effects on projects now planned there.

Cary Adams, regional vice president of real estate for the May Department Stores Inc., the owner of Hecht's, said the proposed changes, if adopted, would act "as a disincentive" to the Hecht Co.'s plan to relocate its downtown store to the Metro Center Project. "Imposition of such requirements will be detrimental to the Hecht Co.'s presence in the downtown," he warned.

James Rich, director of development of the Pennsylvania Avenue Development Corp., also complained that the proposals would "create hardships" for many development projects within the PADC area and particularly would threaten the construction of 1,200 housing units now planned for the area.

Their comments came during the final day of hearings held by the District of Columbia Zoning Commission on wide-ranging changes in the city's parking and loading requirements proposed by the D.C. Department of Transportation. After the record is closed on Feb. 25, DOT has 60 days in which to write a report to the commission offering any modifications and final comments on its proposal. Then the commission will take it up again.

Both Adams and Rich focused much of their testimony on the minimum parking requirements that would be imposed, for the first time, on new buildings in the central business district and the Pennsylvania Avenue Development area. They argued that the proposals run contrary to the city's plan to foster development in the downtown area.

Adams told the commission that the changes would require the Hecht Co. to provide 103 parking spaces when it moves from its current location at F and 7th Streets NW to its new site on G Street NW between 12th and 13th Streets although it currently--and legally--has no plans to provide any parking at the site.

The proposed parking places would cost Hecht's at least $1.5 million, would require extensive revision of current building plans which have cost the company more than $1 million already, and would take away precious space now earmarked for retail selling, Adams said.

"These regulations will not result merely in minor changes but, since we are this far into the details of our development at Metro Center, would require a rethinking and re-evaluation of our whole program at that location," Adams said. He noted that the company has been absorbing losses at its current downtown store in anticipation of moving to Metro Center in the near future.

Adams said that several factors already militate against the construction of department stores in the downtown area, including high land prices, which led the city's Redevelopment Land Agency to propose an adjusted price for the department-store portion of the land in the parcel. The land prices make it more profitable to develop an office building than a department store in the District, even though the store provides the city with significant sales tax receipts, he said.

The city's building-height limitation also has an impact on potential department stores, the commission was told. Adams noted that the ceiling in a retail store is considerably higher than in a typical office building. For instance, the floor-to-floor height in the planned Metro Center store is in the 16- to 17-foot range while a typical office building will have a floor-to-floor height of about l0 feet, he explained. As a result, a department store cannot get as many floors on a site as an office building within the city height limitation, he said. Because of that, a portion of the Hecht store at Metro Center will be below ground.

If the Zoning Commission goes forward with the new proposed parking rules, Adams urged that they be applied only to prospective developments and not to those already in progress. An option would be to exempt projects that have received a conceptual approval from a city agency, he said. If the Hecht's plan to move to Metro Center weren't tied up as a result of litigation between RLA and developer Oliver T. Carr, a building permit would have been issued already and the store would be under construction today, with an opening planned for 1984, Adams said. A delay of at least a year is expected.

Rich of the PADC said some of the city's parking and loading proposals would complicate the Pennsylvania Avenue Plan to redevelop the avenue, which already has been reviewed by local and federal officials and approved by Congress.

Some of the District's proposals are potentially in conflict with the PADC plan, he noted. For instance, in order to improve air quality and reduce noise and auto traffic downtown, the plan sets the maximum allowable number of parking spaces for office buildings at one space for each 1,800 square feet of office use. That's the same as the proposed minimum in the city's proposal.

Zoning Commission Chairman Walter B. Lewis wondered if the city's regulation writers read the PADC plan the same way. "I wonder if DOT read it" at all, said commission member Lindsley Williams.

Rich noted that many developments within the PADC area were providing fewer than the maximum spaces allowed because the high water table along Pennsylvania Avenue makes construction there of underground structures, such as garages, very expensive. The minimum parking provisions also would make it more difficult financially to create the housing units now planned in the central business district, east of the FBI building, a task already exceptionally difficult because of the high land prices, he said.

Another provision that was questioned would require hotels to provide off-street parking places for tour and charter buses--a minimum of one space for every 100 sleeping rooms, up to a total of six bus spaces.

A convention-type hotel such as the Shoreham Hotel or the Washington Hilton Hotel might need the bus spaces but a luxury hotel such as the Madison or the Four Seasons does not, Rich contended. "It is very difficult for us to imagine that the Willard Hotel, when restored as a luxury hotel, would need five bus parking spaces--yet it will be required to provide them under the proposed amendments," he said.