The Environmental Protection Agency (EPA) and the US Army Corps of Engineers (USACE) required compensatory mitigation actions to resolve a violation involving the non-permitted fill of coastal wetlands adjacent to the Pacific Ocean. These violations occurred due to shoreline residential development in Grays Harbor County, Washington. The mitigation actions also address impacts to another half-acre of wetlands associated with future residential development on the property, and impacts associated with dredging a portion of an existing wetland.
A previous consultant prepared a Wetland Mitigation Plan (WMP) for the development which proposed the creation of five wetlands along the west side of Ocean Lane and the enhancement of two ponds along the east side of Ocean Lane. This Wetland Mitigation Plan was approved by the EPA in 2006.
Specific goals of the mitigation plans were:
- To create approximately 3.4-acres of scrub-shrub/emergent wetland,
- To enhance approximately 3-acres of wetlands by reestablishing the pond depth to a range of between 0 and 3 feet,
- Install a minimum of 24 pieces of large woody debris within the created and the enhanced wetlands,
- Install a minimum of 5 brush piles containing small woody debris within the wetlands.
In 2010, Soundview Consultants LLC was contracted to provide compliance support and wetland mitigation monitoring services for the project. SVC conducted an extensive review of the previously approved mitigation plans and monitoring reports as well as the responses from agency personnel. We identified numerous inconsistencies and omissions between the monitoring protocols and the data that was reported. In May 2011, after extensive negotiations with Federal regulators, a consensus was reached to amend the Wetland Monitoring Plan to more accurately reflect the plan initially approved by the EPA and USACE.
SVC staff visited the site to determine the additional requirements that were needed to bring the mitigation areas and monitoring reports into compliance with Federal regulations. SVC determined that several monitoring plot locations originally established near the wetland edge or in wetland-upland transition zones made accurate assessment of wetland conditions not only difficult, but potentially inaccurate. The monitoring plots were relocated, when possible, into an area that was close to the original location but that provided a more accurate assessment of wetland or upland conditions. Relocation of these monitoring plots was approved by regulatory staff. Permanent photographic points were also established at 12 locations to collect photographs and document the progress of the mitigation.
The general mitigation goals of the project are to offset unavoidable impacts of the existing and proposed development, to achieve no net loss of wetland functions, and to improve existing habitat. Habitat conditions are expected to improve throughout the monitoring period and wildlife use of the wetlands will increase over time as the site matures and provides more cover.
The success criteria for the wetland creation areas are:
- Establishment of hydrologic [wetland] conditions,
- Colonization of native shrub and emergent plant species, and
- Increase in wildlife usage.
The success criteria for the wetland enhancement areas [existing ponds]:
- Colonization of native shrub and emergent plant species,
- Salinity not to exceed 4 parts per thousand (ppt),
- Existing ponds will have a maximum depth of 3 feet,
- Invasive plants will be less than 10 percent of the area.
SVC has been monitoring the created wetlands and the wetland enhancement areas twice a year, in the spring and in late summer, for a period of 10 years to ensure these goals are being accomplished. Water depths in the two large ponds have been measured at between 16 inches and 30 inches. Numerous native pioneer tree, shrub, and herbaceous species are becoming established within the wetland buffers in areas disturbed by the mitigation action. Most buffer areas contain undisturbed native vegetation. The results of the 2013 monitoring study indicated that the enhanced ponds were inundated and/or saturated throughout the year. The 2015 monitoring study shows the created wetlands had near 100 percent cover of emergent plants and are interspersed with shrub species, predominately willow. These results show that this mitigation site is meeting or exceeding the performance standards.