Kawa Ditch
Background
Kawa Ditch is located in Kaneohe, Oahu, on the east tributary of Kawa Stream. It is situated within a 40-foot wide right-of-way under the jurisdiction of the City and County of Honolulu. The ditch is surrounded by privately-owned residences and has been used primarily for drainage purposes. It was improved in the early 1960s in conjunction with various Pikoila Tract Subdivision developments. These original improvements consisted of realignment and installation of concrete lining at the ditch’s 90-degree turn and at major drain outlets entering the ditch. Over the years, erosion along the channel bottom had resulted in undermining the concrete lining around the drain outlets which were in danger of falling into the ditch. In addition, Kawa Ditch was not compliant with current Drainage Standards of the City and County of Honolulu (2000).
Description of Work
Our services included preparation of the engineering report, environmental permitting documents, construction plans and specifications as noted below:
- Conduct field investigation to examine the existing conditions and to identify potentially unstable areas that are exposed or undermined due to erosion.
- Determine hydrologic criteria based on USGS quad map and aerial topographic survey and City’s drainage standards.
- Review prior record construction plans to quantify design discharge flows of various culverts and lines emptying into Kawa Ditch.
- Evaluate flooding history in the vicinity of the project site.
- Perform hydraulic analysis using HEC-RAS computer modeling program.
The following environmental documents were then prepared to secure necessary permits and approvals:
- Final Environmental Assessment/Negative Declaration
- Department of the Army Nationwide Permit
- Section 401 Water Quality Certification (waiver)
- Stream Channel Alteration Permit
- Coastal Zone Management (CZM) federal consistency determination
Project Owner
Dept. of Design and Construction, City and County of Honolulu
Firm's REsponsibility
Engineering Study, Environmental Permitting,
Design, and Services During Bidding/Construction
Completion Date
2008
location
Kaneohe, Oahu, Hawaii
