Ada County Highway District

Traffic Resumes on Warm Springs Avenue

Update: April 21, 2017

Warm Springs Avenue Reopens After Three-Month Closure Due to Boulder Threat

Spring weather and work to dislodge the remaining, precarious rocks allowed the road to be reopened to traffic on Friday. Workers finished the $25,000 remediation, clearing fallen rocks, removing teetering boulders and reinstalling concrete guardrails along the slope.

“We didn’t want to reopen the road until we were out of the freeze-thaw cycle,” said John Kirk, ACHD’s deputy director of engineering. “We believe the Mesa will remain stable enough to allow regular traffic to resume.”

In coming weeks, the ACHD Commission will hear options for longer-term treatment of the eroding slope, which frequently sheds rocks in the winter, particularly during years of heavy snow and prolonged cold.

Warm Springs was closed on January 10, 2017 when several boulders fell onto the street, forcing a closure from Starcrest Drive to East Parsnip Peak Drive. Starview Drive also was closed from Warm Springs to South Mill Point Lane because of falling rocks.

Starview reopened in early February, after rocks were cleared and 100 feet of new guardrail was added.

In January of 2015, Warm Springs Avenue was closed for two weeks after a 50-ton boulder fell onto Warm Springs Avenue. After a contractor removed a number of rocks, ACHD crews placed more than 1,200 feet of concrete guardrail along two areas at the foot of the Mesa to block stones from getting to the road.


Update: April 5, 2017

The ACHD Commission on Wednesday approved the a rock scaling plan to reopen Warm Springs Avenue, which calls for a contractor to pull down the remaining loose boulders and remove all of the previous debris caught behind the existing barriers. Commissioners also heard about longer-term projects to stabilize the hillside but those options will not be considered until more research has been completed to evaluate the effectiveness and potential costs. Work is expected to be completed by the end of next week.


  Watch the Commission Meeting item


The Mesa's face has generally stabilized since late February, after falling rocks forced the closure of the road in early January.

Update: March 31, 2017

Now that the Mesa's face has remained stable, the ACHD Commission on Wednesday, April 5, 2017, will consider a recommendation for interim steps to improve safety and reopen the road. The plan calls for the removal of loose rock still on the slope as well as previously fallen stones behind the safety railing. No new boulders have fallen since Maintenance crews cleared the asphalt on February 22nd.

If the Commission approves moving ahead, a contractor will be hired to clear the loose material, which will allow for the reopening of the road upon completion, provided the slope stays stable. The Commission meeting starts at noon on Wednesday.

Update: February 22, 2017

ACHD crews this afternoon will remove rocks from Warm Springs Avenue between Starview Drive and Starcrest Drive, a necessary step toward the possible reopening of the road. Clearing the fallen rocks will allow us to monitor the area for any fresh boulders. If the hill appears stable in coming days, the ACHD Commission may be asked to reopen Warm Springs.

Update: February 9, 2017

Starview Drive was reopened today at noon.

Update: February 8, 2017

Today, the ACHD Commission voted to approve an interim safety treatment so that Starview Drive can be reopened to the travelling public. Starting today, crews will begin to install 100 feet of new concrete guardrail on the west side of Starview Drive. Additional temporary signage and lane markers will be installed to alert motorists to the new lane modifications. It is anticipated that Starview Drive will be reopened by the close of business tomorrow (Thursday, February 9).

Warm Springs Avenue will remain closed due to recent fallen rocks; however, the closure has been pushed back to exist between Starview Drive and Starcrest Drive.

Starview Drive and Warm Springs Avenue have both been under heavy monitoring since rocks first began falling earlier this winter after a freeze/thaw/rain cycle prompted more erosion of the hillside. Motorists should be aware that the area on Starview Drive is still part of an active landslide, and should be watchful and use caution when navigating this roadway. ACHD staff will continue to diligently monitor both of these roadways. It is anticipated that, with the assistance of a local geotechnical firm, ACHD staff will have more future long-term solutions to present to the Commission by the end of March 2017.


Update: January 30, 2017

ACHD crews will remove fallen rocks on Starview Drive starting today. The road will be monitored and if it remains suffiiently boulder-free in coming days may be considered for at least partial reopening. Warm Springs Avenue, however, continues to shed numerous stones and cannot be considered for reopening at this time, ACHD's Engineering and Maintenance departments concluded on Friday.

A geotechnical firm has been hired to study the situation and provide options for interim steps and a long-term solution to the long-standing problem. A report is expected by mid-March.



Numerous large rocks broke loose the week of January 9, 2017 from the Warm Springs Mesa, forcing the closure of portions of Warm Springs Avenue and East Starview Drive until the slopes stabilize and the rock fall risk diminished. Rocks continue to fall, as can been seen in the last picture on this page, taken Wednesday, January 18th

Warm Springs Avenue is closed from Starcrest Drive to East Parsnip Peak Drive, and Starview is closed from Warm Springs to South Mill Point Lane. Residents of the Mesa will still be able to use Starcrest Drive and Windsong Drive to access the area.
Those needing to travel downtown from east of the Mesa will have to use Parkcenter Boulevard until further notice.

The rocks are likely falling because of the recent rain and thaw, which has destabilized the fragile slope where rocks often move in the spring. The winter’s weather pattern – snow, followed by weeks of subfreezing cold, followed by rain and higher temperatures – is believed to have touched off a fresh round of erosion.

In January of 2015, Warm Springs Avenue was closed for two weeks between Starview and Starcrest after a 50-ton boulder fell onto Warm Springs Avenue. After a contractor removed a number of teetering rocks, ACHD crews placed more than 1,200 feet of concrete guard rail along two areas at the foot of the Mesa to block stones from getting to the road.


Some individuals in recent days have removed barriers to access the rock slide areas of the closed roads. ACHD asks people to obey the closures to ensure their own safety, as well as the safety of emergency responders.


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