Major work on the Washington & Old Dominion biking and hiking trail is expected to begin this summer along 21 miles between Vienna and Leesburg, according to the Northern Virginia Regional Park Authority.

But there may be a two-mile gap in Herndon, where town officials have been holding up approval of park authority plans, down to such details as permits for minor drainage ditches.

The project, which will cost $1 million, goes out to bid this week. Under current plans, four bridges would be built, nine additional miles of the trail -- from Vienna through Herndon -- would be built as far west as Rte. 15 in Leesburg.

But the $200,000 in work slated for Herndon is being advertised separately because of uncertainty over that section of the 42-mile trail. If the town fails to agree to the improvements within the next few months, park agency staffers say they will recommend the $200,000 be used elsewhere along the W&OD trail this summer, which stretches from Arlington to the Blue Ridge foothills in Purcellville. Herndon Mayor Thomas D. Rust said last week the town wants some concessions from the Park Authority before it approves any of the authority's plans for Herndon.

The town wants to own the land under the Herndon railroad depot, to keep an employe parking lot that now straddles the W&OD trail and approval for several future streets that would cross the bike and horse trail.

The Town Council and planning commission have scheduled public hearings on the plan July 7 and 8. Town planner Norman Hammer said he hopes an agreement with the Park Authority can be worked out after that. The Park Authority is expected to award contracts on the rest of the trail work before the hearings.

The hold-up by Herndon has been called "a kind of blackmail" by David Hobson, director of capital projects for the Park Authority.He said the park agency has "tried to be a good neighbor everywhere," and already has made numerous concessions to Herndon.

"Herdon is the only one of many jurisdictions we pass through where we have encountered obstacles," Hobson said.

Mayor Rust and the major consideration is making sure that Herdon gets the land under the depot. The depot is owned by Herdon; the land is owned by the Park Authority.

"We've been trying to get that for three years," Rust said. "It's the town's most historic spot, they promised it to us at one time."

The Park Authority has balked at giving Herdon the land, and instead has offered a free, long-term renewable lease on the land. "We don't plan to sell any park land," says Hobson, "and, in fact, this is the only long-term lease we've offered to anybody other than utility rights of way."

Another area in dispute is the 46-car municipal parking lot. The lot covers most of the 100-foot-wide right of way beside the depot. The town wants to retain the parking lot on W&OD park land, while the Park Authority wants at least half of the lot turn up to allow bikers, hikers and horses to pass on a separated trail. The authority wants the other half of the lot opened to parking for the general public.

Another issue has been getting bikers, hikers and horses across Elden Street, which is now being widened to four lanes.The safest way, says the Park Authority, would be a traffic light that can be activated by trail users but which would be synchronized with nearby lights.

The Virginia Department of Highways and Transportation already has agreed to install such the light, but Herndon officials say they may want trail users to cross at the existing traffic light at Monroe Street, about 100 yards north of the trail.

"We are not trying to be difficult to deal with or to give the park authority a hard time," says Hammer. "We have our own hike and bike system and have said constantly we are looking forward to having the trail come through Herndon . . . but we want to study all the issues and approve the trail as a package deal. Are we had guys just because we want to take a look at these things?"

"It's been a one-way street so far," says Hobson, with the Park Authority either granting Herndon requests to use park land or tacitly agreeing to the town's unofficial use of park land, "and the town so far refusing to approve anything we propose."

A good example of the town's attitude, although "it's a petty thing," says Hobson, is the widening of Crestview Drive, which crosses the W&OD trail at the west end of town.

Even though Herndon had only a 30-foot right of way, it built a 35-foot-wide road. The town asked permission to increase the width only after the road was under construction -- and after the Park Authority had complained. Then, without further notice, it added a sidewalk, taking another 6 to 10 feet of park land.

"They had no right of way, they simply expropriated our land," said Hobson. "We don't argue with the need for the street or the sidewalk, but you usually get permission before doing construction work on somebody else's land."

Town officials claim the widening of Crestview was just a misunderstanding.