Rockville is trying again.

If we practiced effective environmental planning in this country -- if collectively we were to arrange our urban regions with the care with which most Americans arrange their living rooms -- Rockville would be an attractive, bustling town, one of several satellites circling the center city of Washington.

The heart of Rockville would be the business and cultural center for the people who live in the area. In addition to county government (Rockville is the Montgomery County seat), the town would contain the industries and services medical clinics, automobile repair shops that now litter suburbia like so much garbage.

By concentrating urban business in the satellite town, suburbia could properly tend to its business, which is to be clean, green and residential.

But we have no effective environmental planning. As a result of this criminal neglect, we have such visual punk as Rockville Pike and sweet little Rockville has been overrun by urban sprawl. If the City of Rockville had torn down the old courthouse, as was suggested a dozen years ago, the town would now be little more than a name attached to a traffic jam.

But luckily, preservationists prevailed, and the old courthouse with its knoll of old trees has survived. Most everything else in the heart of Rockville was bulldozed to pave the way for urban renewal. Driving the bull-dozers was $4.5 million in federal funds. The result was disaster.

The old urban renewal plan was drawn up by Robert L. Geddes, dean of the architecture school at Princeton. It was exciting. There was to be a heady concentration of stores, offices and apartments, enhanced with plazas and walkways. The old courthouse was to provide historic continuity and the soon-to-be-completed Metro station was to provide new residents and customers. There was to be plenty of underground parking. Rockville's new downtown was to be all pedestrian, with vehicular traffic routed around it.

But all that came out of the upheaval was a dismal, half-empty and hard-to-get-to shopping mall and an unsightly corrugated metal barn for indoor tennis. Visually, Rockville is worse off today than it was before urban renewal.

The bitter lesson is that a well-meaning mayor and council, a pretty plan, and the promise of federal money are not enough to pull a city out of the morass that the absence of effective environmental planning has created in this country. Other industrialized countries have both regional and national planning.

Specifically, what seems to have gone wrong in Rockville, as in many other cities where urban renewal failed, is the Alphonse and Gaston approach.

First the residential developers played Gaston. They said, "We will be charmed to build the pretty apartments and rowhouses Mr. Geddes has sketched for us. But first you must give us roads and shops and parking and those lovely park benches and lampposts. After all, my dear Alphonse, you surely do not expect our customers to live in a construction site."

To which Alphonse, the government, replied: "You do not understand, Gaston old boy. We must have residents first to fill the shops and parking garages and benches. We need their tax money to pay for the roads and the lampposts."

With nobody wanting to go first and no department store willing to move in, the shopping center remained isolated and dismal. Besides, department stores, like carbinieri , always come as a pair. The Rockville urban renewal plan provided only for one, with the Metro station on the other end of the enclosed mall. There might have been another department store somewhere along the side. But in shopping center planning wisdom a side store does not count. Besides, the Metro station was still years and years away. (It is now scheduled to open in 1983).

What a city needs to renew itself, in addition to a good, strong, practical plan are five things:

First of all it needs a leader, a tough boss, who can knock the Alphonse and Gaston heads together. Boston's renewal is a success because of Edward J. Logue. Baltimore is a success because of Robert Embry. There would be no Paris, as we know it today, without Baron Manfred Haussmann, who was an S.O.B. So was Washington's "Boss" Alexandria Shepherd.

The other requirements for urban recovery are: a sure knowledge of where the money is coming from, strong political backing, sustained citizen participation, and, perhaps most important of all, an organization that can actually build as well as plan.

Now Rockville has another plan for its 438-acre downtown center. The drawings are beautiful, and the ideas behind them are innovative and exciting. But most of the the other requirements are still missing.

This second go-around, conceived by Arthur Cotton Moore Associates, has undoubtedly greater popular appeal than the first. It is not stark, brutal Modern. Moore has drawn a number of new buildings that almost mirror the historic building and imbue the rest with a gentle historicism. Moore's urban design would create a quaint complexity -- it is the idea of pluralism translated into a cityscape. What it adds up to is the "feel" of a small town.

If built as drawn by Moore, Rockville's town center might be as spectacular a success as Boston's Quincy Market -- and that is a smash hit.

The centerpiece of Moore's design is the old courthouse, which is now being rehabilitated for offices and storage. Moore would turn it into a dinner theater, which is obviously a more dramatic use for the old pile. But the idea is risky, what with the quality of theater and dinners out there in the sticks.

In front of the courthouse knoll, Moore would build a round, landscaped plaza with a driveway. He would allow cars back into an area from which they are now banned, taking the risk that they park all over the manicured laws and leak oil all overthe ivy.

Opposite the courthouse and crowned with two Neo-Neo-Romanesque towers, almost identical to the of the courthouse, Moore would like to see a farmers' market, the new urban salvation and, I hope, a more durable fashion in urban chic than scented candle boutiques.

Moore would hide the architectural sins of that dismal shopping center with one of those witty Arthur Cotton Mooreisms that make the architect one of the younger stars of his profession. He would build a "solar fountain" that would catch sun rays in an array of triangular, voltaic solar panels placed on stilts. The electricity derived from this device would operate the pump of the water fountain.

Other special features of the proposal are an old-fashioned double-decker bus, a meandering walkway, an elevated pedestrian bridge to the Metro station (which should have been located in the center of downtown but wasn't) and a hotel conference center and high-rise office building that is to mark Rockville on the horizon.

The most innovative of Moore's proposals is his device to hide the chaotic mess along Rockville Pike and give the city a dignified approach. He would build berms along both sides fo the highway, green dikes that contain the strip-developed ugliness. At intervals, the berms would give way to billboards, no higher than a berm, to announce the store or used-car dealer behind it. There would be wide oppenings into the parking lots.

Moore and James Davis, Rockville'splanner, hope to place all utility lines inside the berm to unclutter the highway. They are looking for a grass or groundcover that will be economical to maintain. A greenway littered with beer cans is worse than none.

According to City Manager Larry N. Blick, the chances for building something like this are more auspicious than they were a decade ago. The city now owns the fallow urban renewal land it bought from the feds. It also obtained $3 million in bank loans to get things started.

Metro is a relity. Its elevated railway is under construction. You can see it. Despite the urban renewal disater, Rockville has attracted an impressive number of new businesses and corporate headquarters, notably General Electric, Solarex and General Business Service.

County government is growing into an ugly, monumental office and courthouse complex now under construction in the downtown redevelopment area. Since the sewer moratorium was lifted two years ago, demand for new housing and small industry in the I-270 corridor is still pent up.

By all accounts, the Moore proposal is being well received. Who would object to pretty green walkaways, a picturesque trolley on rubber wheels or a "solar fountain"?

But who would build them?

As in the old urban renewal procedures, the whole enterprise will be up for grabs by willing developers as soon as some zoning matters are resolved. They are likely to come in one project at a time. While the city, which sells the land and provides building permits and sewers, has some measure of control, it cannot make the developers build to Moore's specifications. Builders will be cutting corners. They will use the cheapest architects they can find. They will use some godawful aluminum trellises or something because the wifey saw one like that in Miami and adored it. Before you know it, you have K Street in Rockville.

The best -- and probably only -- hope for realizing Moore's admirable plan, and thereby setting a national example for the rebuilding of small towns in metropolitan regions, is for the city to exercise full control.

This can be done in two ways. Either the whole thing is built by a nonprofit Rockville Town Center Development Corporation, which then leases the stores, markets, hotels, etc., or a large part of it -- the critical mass -- is built by one developer who would work with Moore and the city on the practical refinements of what is as yet only a collection of lovely sketches.