Lessons Learned from Phase II Site Construction and Monitoring
Local, State and Federal permitting requirements should be thoroughly researched and conversations with regulators regarding proposed site work should begin before or very early in the permitting process so that the project schedule will not be adversely impacted. Potential environmental concerns that can cause significant project delays include concerns about rare and endangered species and their habitat, and inventorying/preserving archaeological resources. Above all, incorporate flexibility into the project construction schedule to compensate for unavoidable delays. Oftentimes, the environmental resources of a project site are not completely known or inventoried until a project is proposed and in the "permitting pipeline." This is the point that the presence of rare and endangered species or archeological resources is either confirmed or, in some cases, discovered. The Urgiel Upstream project experienced significant delays due to permitting agencies' concerns about the potential impacts construction might have on a rare species of dragonfly and Bald Eagles plus the need to resolve segmentation issues raised during the Massachusetts Environmental Policy Act (MEPA) review process.

Project funding constraints may adversely impact the project construction schedule. Although company budgets and fiscal year spending requirements are not always able to accommodate specific project construction schedules, to the extent possible, these funding constraints should be anticipated and reflected in a flexible project construction schedule.

The timing of the start of site construction is a critical factor in the overall stability of the site and the viability of the installed plant material. Unlike traditional bank armoring techniques such as gabions and rip-rap which can be installed at any time of year, bioengineering bank stabilization techniques use live woody and herbaceous plants and plant material that must be installed during certain times of the year to ensure viability. For the Urgiel project, the permitting delays pushed the start of construction back to October. The site was cleared, graded and seeded, and the stone toe was installed by the beginning of December, but no vegetation could be planted due to adverse weather conditions. The site vegetation was not planted until five months later, in May. At the Phase I s.319-funded site known as Crooker, the site design called for dormant brush to be installed. However, site construction commenced in June, less than ideal conditions for the installation of dormant brush which should be installed during the colder months of the year. Although attempts were made to keep the brush dormant by storing it in a refrigerated warehouse, a fungus developed in the cuttings and those that survived were less healthy and vigorous, and once on-site and exposed to the heat, they deteriorated even more rapidly. To replace the lost dormant brush, rooted cuttings were purchased. However, these plants were expensive and delicate and required special handling.

To the extent possible, incorporate contingency design elements into the project site design. For example, the start of construction was delayed at the Urgiel site for several months which resulted in the site being left unvegetated for five months during the winter and early spring. Although attempts were made to secure the site for the winter with a staked erosion control blanket, the spring freshet flows supersaturated the soil in the lower portion of the bank. The soil slumped and was eroded in several places. A contingency design element for this situation could have been the use of a stronger erosion control blanket or other materials or methods for ensuring that an essentially bare slope remained stable during the winter months and provided adequate resistance to the erosive forces of the spring freshet flows.

A variety of bioengineering techniques have been effectively used on this reach of the Connecticut River. These techniques have successfully reduced erosion as a source of non-point pollution, protected private property, including prime agricultural land, and stabilized the eroded riverbank. Attempts were made to further "soften" and refine the bioengineering techniques for the Phase II site.

The species of herbaceous and woody vegetation, including native species, selected for installation at the Phase I and Phase II sites have flourished and, thus far, have not been displaced by invasive species. One of the project goals was to enhance habitat value by reintroducing native plant communities. It is important to inventory the native species on and around the project site prior to construction and incorporate native species into the design. A variety of grasses and other herbaceous vegetation, woody shrubs, willows, and silky dogwood are thriving at the sites. Thus far, only a few stems of three invasive species have been identified in the sampling plots at the Urgiel site, including: Oriental Bittersweet (Celastrus orbiculata) in the lower slope; Purple loostrife (Lythrum salicaria) in the lower slope and stone toe; Black Locust (Robinia pseudoacacia) in the lower slope. These species are classified as invasive by the Massachusetts Division of Fisheries and Wildlife.

Woody vegetation was installed at the Phase I and Phase II sites using several techniques, including live stakes, dormant brush, pre-vegetated mattresses, tubelings, and one-gallon size potted woody vegetation (native shrubs). The use of potted plants at the Urgiel site did offer greater flexibility in site design and greater diversity of species. The vegetation monitoring protocol developed for the Urgiel site established success criteria that could be used to evaluate the whether the use of the four bioengineering bank treatment types had achieved project goals. Monitoring of the Urgiel site was conducted in October/November 2002 and June 2003. The success criterion of 60-80% for first year survival of the planted woody and herbaceous vegetation was exceeded with 100% of the vegetation counted in the sampling plots being healthy. The success criterion of 80-90% for second year vegetation survival of the planted vegetation was exceeded with 100% of the vegetation in the sampling plots being healthy. For the October/November 2002 monitoring round, the success criterion of requiring an average of 75% vegetative cover in each treatment type (except the stone toe) was met in the top of bank and upper bank treatment area with 85% and 95%, respectively. The lower slope had 62.5% vegetative cover. In June 2003, the percent vegetative cover for all treatment types except the stone toe exceeded 75%. The average percent total vegetative cover for the stone toe increased from 35% in October/November 2002 to 40% in June 2003.

Bioengineering sites are hospitable sites for the establishment of volunteer (not planted) vegetation, particularly herbaceous species. There was a surprising diversity of volunteer herbaceous species observed in the stone toe sampling plots at the Urgiel site. As an example, native vegetation which had not been planted during construction included: Devil's beggar-ticks (Bidens frondosa), Mad-dog Skullcap (Scutellaria latifolia), Path-rush (Juncus tenuis) and 3 Square sedge (Dulichium arundinadeum).

Monitoring of the site during construction is critical to ensure that the contractor adheres to design specifications. The consultant specified a native seed mix for the Urgiel site after researching local native herbaceous vegetation and consulting with state regulators concerned with native species and their habitat. Unfortunately, the species in the native seed mix are not found at the Urgiel site. Although the contractor has provided a verbal assurance that the native seed mix was used, no written evidence or other certification has been provided. There are several possible reasons why the species in the native seed mix are not present, including: the wrong seed mix was spread at the site; the native seed mix was applied during December, less than ideal conditions; or the topsoil brought to the site was "contaminated" with dormant clover and grass seeds. Daily, on-site monitoring during critical periods of site construction will help to ensure that the contractor adheres to design specifications.

When structural problems appear, the assessment and prompt repair of the failures is essential. The original design for Urgiel did not include provisions for reinforcement of the interface between the top of the stone toe and the bottom of the vegetated bank (e.g., coir fascines) like the designs for the Phase I sites. In the late Fall 2002, it became apparent that this interface could not withstand the erosive forces of pool fluctuations and other changes in water level/velocity (boat wakes, etc.) A shelf had been eroded in this area that extended the length of the site and was approximately 2 to 3 feet wide. Coir fascines and live willow stakes were installed in this area in November 2002 to strengthen this interface. Subsequent site monitoring indicates that this interface withstood the Spring 2003 freshet flows and the willows are well established.

Bioengineering techniques used at the Phase I and the Phase II priority erosion sites in the Turners Falls Power Pool have achieved the project goals of:
  • Reducing erosion as a source of non-point pollution (sediment) to the Connecticut River;
  • Stabilizing eroded riverbank;
  • Enhancing habitat value by reintroducing native plant communities; and
  • Protecting private property, including prime agricultural land.