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This report constitutes the second phase to document the water quality benefits of a stream restoration in the coastal plain of North Carolina. This phase compares the pre-restoration and post-restoration states of the water quality and hydrochemical signature of ‘the canal’ at the Claridge nursery in Goldsboro, NC. We made the hypothesis that a robust way to quantify the water quality benefits of this stream restoration was the use of cumulative nutrient load indicators. However, these indicators required the use of state-of-the-art instruments capable of capturing flow and water quality on a near continuous basis over the long term. After meticulous correction and all the necessary verifications, we were able to show that the restoration of the Claridge nursery canal, effectively creating a flowing wetland, was able to lower the nitrate loads by about 30% over three post-restoration consecutive years. This was accompanied by an overall carbon sequestration. The seasonality of the nitrate retention suggests that much of the nitrate unaccounted for was associated with the growth of vegetation, either through plant uptake and/or through denitrification associated with the release of organic matter from dead vegetation and the exchange conditions that they provided in the channel and with the floodplain. Increased residence time associated with the aquatic vegetation working as a filter time likely increased the capacity of the stream to retain nitrate. The seasonality of the nitrate retention may suggest that shorter monitoring periods could be chosen to represent a ‘summer’ vs. a ‘winter’ effect. However, averaging these effects would not necessarily represent the effective benefits over the long term. Instead, we suggest that monitoring should focus on cumulative indicators used over the long term for projects for which there is a high potential for nutrient retention. Fewer projects may have to be monitored, but using the necessary investment.

FHWA/NC/20YY-NN, Appendices included as Supplemental File, Stormwater conveyance networks contribute to stream degradation and instability either through direct discharges of sediment or by eroding gullies downslope of pipe outlets. To limit erosion downslope of pipe outlets, current regulations require the 10-yr, 24-hr peak velocity discharged to a vegetated area to be less than the downslope soils’ permissible velocity. Otherwise, the conveyance system must be redesigned. The effectiveness of this design standard has not been evaluated. North Carolina State University assessed 60 pipe outlets in the Piedmont and Mountain physiographic regions of North Carolina to identify which watershed and downslope characteristics influence the severity of erosion caused by pipe outlets. The effectiveness of the current standard was also assessed. Six assessed sites in Raleigh were additionally monitored for hydrologic, hydraulic, and water quality impacts. These data were also used to evaluate the effectiveness of a swale with (1) rip-rap, (2) well-established vegetation, (3), check dams with mowed turf grass, and (4) check dams with well-established vegetation to limit downslope erosion. The results indicate the current standard does not limit downslope erosion, and designers should consider limiting the 1-yr, 24-hr peak velocity to the permissible velocity. Designers should also consider the downslope soil and vegetative conditions to reduce the potential for gully erosion. Designers can use the predictive tools developed from the data to help determine the optimal discharge point for pipe outlets. Preliminary results suggest turf grass swales with check dams may mitigate the potential for erosion downslope of pipe outlets. However, this design should be validated with field-scale studies before standards for pipe outlets are revised.