Stormwater and erosion control ‘inadequate’ at Palisades construction site according to DPW

The Department of Public Works has issued a notice of violation to the developers of the Palisades subdivision, citing “inadequate control of stormwater and erosion control features during construction,” which it says led to the Oct. 15 landslide in East Hagåtña.

DPW issued the notice on Oct. 22 to the project’s developers after determining that the failure was caused by overtopping of rain runoff from a temporary detention basin near the site.

According to the notice, drone footage and on-site inspections revealed that most of the site’s runoff flowed into the basin, which then overflowed.
“This damage caused significant inconvenience to the people of Guam, damages to Government of Guam assets, and expenses to the DPW for the cleanup,” wrote DPW Director Vincent P. Arriola in the notice. 

Arriola said that both the existing Naval Air Station down drain, which channels storm water from the top of the cliff to an outfall in Hagåtña Bay, and the newly constructed drainage inlets at the Palisades site were blocked, contributing to the overflow and subsequent landslide.

DPW has directed the Tutujan Hill Group, the construction and contracting company attached to the Palisades development, to temporarily retrograde the site so that water does not collect near the cliff face as an immediate corrective measure.

Arriola wrote that the following conditions will also be added to the notice: 

• Conduct a land survey to clarify property boundaries and distinguish owner responsibilities from those of the government regarding drainage and cliff conditions;
• Perform an engineering survey using a LiDAR drone of the cliff face and site to document surface conditions and impacts of site flooding during construction; 
• Perform a hydrologic and hydraulic investigation of existing conditions and predicted conditions based on current land use; 
• Perform a geotechnical investigation, focused on slope stability and cliff face integrity with solutions for long-term stabilization; and 
• Re-examine the drainage study to determine if implementing a more conservative design would be in the interest of prospective lot owners and the Government of Guam as the foundation for both temporary and permanent drainage system designs. 

In an Oct. 22 statement, Tasi Vista Development, the developer of the subdivision, said it is “carefully reviewing the supplemental notice of violation by DPW.”

The company said that, in coordination with its contractor and engineering firm Duenas, Camacho & Associates, it has been working with the Guam Environmental Protection Agency and other agencies on a supplemental mitigation plan.

That plan was approved by GEPA on Oct. 22 and is expected to be fully implemented by Oct. 25, according to Tasi Vista. mbj