That's about to change. The City of Walnut Creek will open much of upper Lime Ridge this fall capping more than twenty years of work by citizens and community leaders, the elected and appointed officials and staffs of Walnut Creek and Concord, the East Bay Regional Park District, Save Mount Diablo and the Walnut Creek Open Space Foundation.

Well known to residents of central Contra Costa, Lime Ridge, rolling from one knoll to the next, is the greenbelt trailing from Diablo to Concord's city center and separating that city from Walnut Creek. Ygnacio Valley Road and Treat Boulevard cross the Ridge and the Contra Costa Canal and Trail follow its western base. Although these trails are near the Open Space's lowest elevation, they provide incredible panoramic views of Mt. Diablo and the Ygnacio Valley, the Carquinez Straits, Briones, Lamorinda, and the Berkeley-Oakland hills. At an elevation of 1001 feet, the Open Space's highest peak is 400 feet above the Canal Trail.

Most of Lime Ridge is oak-studded grassland. Paradise Valley is especially beautiful, but much of the park is made up of rolling hills with wide ranging views. There are a few ephemeral streams and a few stock ponds, but in general the preserve has less water than other similarly sized areas.

The decades since quarrying ended have allowed restoration to take place, and there is rich biological diversity. And, although the quarry scars aren't natural, they have become home to many species of wildlife. The peak, which is crowned with communication towers, and part of the Open Space's north slope are covered with chaparral, and include rare and endemic species such as the Alameda whipsnake, the Diablo manzanita and the beautiful Mt. Diablo Globe Lily. Deer, coyotes, hawks, eagles, and a variety of songbirds and reptiles are common, as is an occasional bobcat.

Easily accessible, the Open Space is certain to be well-used. Surrounded by residential areas on the east and west-the Woodlands, Pheasant Run, Rancho Paraiso and the rest of the Northgate area in Walnut Creek, the Navarrone, Cowell, and Crystyl Ranch neighborhoods in Concord. the difficulty will be to keep it from being over-used. Because of this, the city has wisely taken a 'go-slow' approach to use, building few trails initially and allowing grazing, and dogs on and off leash, in select areas.

One of Mt. Diablo's Fossil-Laden Barrier Ridges Lime Ridge has had more lives than the proverbial cat. In geological time, long before the mountain's peak became visible, Central County was repeatedly flooded by shallow seas into which clays and other sediments settled.

Sandstone, limestone and other soft rock layers were formed. Some of these sedimentary layers were rich in organic materials; coal developed and thick beds of shells were deposited (thus, 'Shell Ridge').

Meanwhile the oceanic Pacific tectonic plate moved underneath the edge of the North American Continental plate slowly pushing up coastal mountain ranges. At weak spots, the older, underlying structure pierced upward through sedimentary rock. Around five million years ago, Mt. Diablo, began an upward journey as a piercement structure.

The younger rock layers above Diablo were forced aside, millimeter by millimeter, sometimes lifted into vertical formations. These softer barrier ridges eroded into canyons and steep slopes surrounding the main peaks exposing lime, coal and various fossils which we easily find along ridgelines and in quarries. Many of the Diablo region's place names-Shell Ridge, Oyster Point, Fossil Ridge, Coal Canyon, Oil Canyon, Black Diamond-reference this geology. Hence, Lime Ridge is named for the lime deposits found there.

Artifacts and relics belonging to Native American people have been found in several places on Lime Ridge leading us to believe they collected acorns and hunted there. At later dates, people of Europeans descent introduced cattle, grew wheat, and then returned to grazing as the soil declined. Cowell Company began intensive quarrying of lime and sand, to be used to make cement and glass.

Until World War II, the population of Walnut Creek and Concord combined was less than 2000; fifteen years later the population had swelled to 46,000. Pressure on Lime Ridge and Mt. Diablo's foothills increased as undeveloped flat areas became less common and view lots more valuable. Subdivisions began to creep up the slopes.

A New Open Space System - In 1974 a large development was proposed for Indian Valley, adjacent to Walnut Creek and below Shell Ridge; the intent was to grade the ridge to fill the valley, creating an easily developed area. Residents galvanized opposition, and after successfully stopping the development, convinced the County Board of Supervisors to create a recreational district to acquire Shell Ridge. Two regional bonds were passed and Walnut Creek and Concord began acquisition in a variety of areas.

Over time Walnut Creek's Shell Ridge, Acalanes and Sugarloaf Open Spaces were made accessible to the public. Shell Ridge Open Space was extended up Pine Canyon and along ridges to join with the new Diablo Foothills Regional Park and the expanded Mt. Diablo State Park. Together they formed a substantial wildlife and recreational corridor. Walnut Creek and Concord each retained parts of Lime Ridge and Concord soon opened a 174 acre area north of Treat Boulevard known as lower Lime Ridge. Today these areas are heavily used by joggers, hikers, cyclists and equestrians, many of whom reside in surrounding neighborhoods.

Upper Lime Ridge, the area above Treat and closest to Mt. Diablo State Park, remained closed. Totaling approximately 1500 acres at present, these parcels have been subject to more complex management issues than the other open spaces. Nearby development made boundaries, fencing and access points uncertain. Past quarrying created abrupt cliffs and rusted metal and machinery created liability and cleanup issues. Neither city had the staff necessary for management and the area remained closed as a land bank.

In the late 1980's a number of important changes began. As with the creation of the Open Space system, they were the result of tremendous citizen involvement and work by grassroots organizations including Save Mount Diablo and the Walnut Creek Open Space Foundation. The Rancho Paraiso project was approved by the County on the west side of the ridge, including a dedication of half of the 210 acre parcel to Lime Ridge and a trail from the new Arbolado Park.

Concord approved the Crystyl Ranch project on the east side of the ridge with 330 of 512 acres dedicated as open space, much of it to Lime Ridge. This project, which is under construction, includes trails and another new staging area.

In recent years the last private parcels along Ygnacio, all adjacent to the public open space, were proposed for development. In Walnut Creek the 216 acre Newhall North and South development was stopped and the land subsequently acquired with East Bay Regional Park District and City funds. In Concord the 85-acre old Sand Quarry site has been proposed for development; the most sensitive and visible areas will be dedicated to the Open Space, along with a staging area and trail connections.

In the meantime, Walnut Creek hired a new Open Space coordinator and additional staff, began a resources study of its open space system, and undertook public hearings over various management issues-from grazing to whether dogs should be allowed. Several hiking trails have been added to existing fire roads, fencing should be completed this summer, and western access points will open sometime this Fall.

Although the efforts of groups such as Save Mount Diablo aren't complete-long-term goals include extension of the preserve a mile and a half to the Mt. Diablo State Park boundary-there is much to celebrate.

More than twenty years of work are about to come to fruition with the opening of Lime Ridge Open Space. Tremendous citizen involvement, significant public funding, a dozen development projects, and numerous acquisitions have all shaped a new public Open Space. Thousands of people and generations to come will all benefit.