Recommendations 

Planning

Cluster Design. The cluster design helped to reduce overall imperviousness, and increase open space. A cluster approach is recommended for future developments.

LID-based Regulations. Because many waivers were required for the construction of this project, an LID ordinance is recommended to facilitate adoption of this approach in other towns.

Disconnect Stormwater. The percentage of impervious coverage has been related to water quality and habitat impairments. As part of the low-impact development approach, disconnection of stormwater sources should be considered at the planning phase. Common disconnects include gutter design (to ensure that downspouts drain to pervious surfaces), road and driveway design. By emphasizing disconnected stormwater, the thresholds identified for water quality impacts from traditional developments may not apply.

Construction

Compaction. Soil compaction due to heavy equipment use of a temporary access road caused problems with infiltration in rain gardens and swales. Therefore, it is recommended that soil compaction be kept to a minimum, and that hard-surface roads are used for access during construction.

Undisturbed Soils. To help maintain the overall infiltration capacity of the soils on the site, it is recommended that as much of the site’s soils and vegetation as possible is left undisturbed.

On-site Supervision. Because LID practices are still fairly new and contractors are unfamiliar with their installation, it is recommended that a person versed in installation of LID techniques is on-site during construction. In addition, it is imperative that this person has the ability to make adjustments to the plan in the field, as necessary.

Earthen Berm. The installation of the earthen berm to reduce export of sediment and runoff worked well, and is a recommended construction best management practice.

Grassed Swales. Due to the fact that grassed swales are vegetated systems and are vulnerable to erosion until stabilized, it is recommended that temporary erosion and sedimentation controls are implemented when swales are installed. See the Connecticut Guidelines for Soil Erosion and Sediment Control (DEP Bulletin 34) for specific recommendations.

Soil Testing. Contractors are accustomed to applying a starter fertilizer to loam when seeding a lawn. This practice occurred at the site, despite the fact that soil tests showed that no fertilizer was needed. Therefore, it is recommended that a soil test is performed when loam is applied to swales or lawns, and that the contractor follows the recommendations. More broadly, soil tests do not include a test for nitrogen, so even if homeowners or contractors have a soil test done, recommendations for nitrogen application are not provided. It is recommended that a nitrogen test be a component of standard soil testing.

Post-construction

Education. The intensive one-on-one education methods that are traditionally thought to produce the most effective behavioral changes did not perform as intended. The involvement of a social scientist might be helpful to ascertain appropriate education methods.

Bioretention Maintenance. Maintenance of the cul-de-sac bioretention area resulted in excessive weed trimming with damage to shrubs. It is recommended that proper maintenance techniques be implemented to ensure proper function, aesthetics and plant health. Such techniques include maintenance of flow paths, surface water storage capacity and mulching to reduce weeds and the need for mowing.

Paver Maintenance. Due to the excessive loading of wind-blown fine particles loaded on to the pavers before construction was complete, the infiltrating ability of the roadway was reduced. Therefore, it is recommended that if a pervious surface has high loading of fine particles, the surface should be maintained by vacuum suction and replacement of the infill materials.

Image of a turf dam.

Turf Dam. The turf has begun to creep over the edge of the roadway in some places. Some consideration should be given to avoid this growth, as it can channel water down the roadway and prevent it from entering the swale.

Fire Hydrant. The fire hydrant on site was flushed at one point, and the infill material on the roadway was washed out in a large area. It is recommended that if this practice is necessary, care should be taken to direct the flush water away from the roadway and into an area that will not erode.

Seed Mix. A special turf seed mix was used at the site that had low fertilizer, water and maintenance requirements. However, several homeowners reseeded large areas with standard seed. Therefore, it is recommended that the use of the special seed mixture is specified in the homeowners’ association documents.

Monitoring

Control. The use of the control watershed was critical in this study to attribute the changes observed to the construction and management practices used, without bias from climatic variations. Therefore, the use of a similar control is advised in future monitoring efforts.

Forested Control. The control used in this project was a previously developed residential area. To make direct comparisons with the pollutant export from undeveloped areas, it would be helpful in future studies to include an undeveloped control with strong protection measures to ensure undeveloped status during the duration of future study.

Sampling Methods. Although the continuous automated sampling used in the project was highly successful, relatively few event-based grab samples were taken. Grab sampling is weather dependent, and is difficult to perform at a remote site. Future projects should consider the proximity of the site if grab sampling is desired. In addition, a local volunteer could be enlisted to aid in collecting samples on evenings or weekends.

Electric Power. Solar panels were used to supply power at various times through the project. However, the ability to connect to the power grid provided more stability and gave more flexibility for sample preservation (i.e., the use of small refrigerators). Future projects should consider connections to the grid when possible.

Further Study Recommendations

Groundwater Effects. Groundwater monitoring was not performed as part of this study. However, the addition of this type of monitoring would help to answer questions about the fate and transport of pollutants as a result of the LID infiltration practices used, versus traditional stormwater methods.

Social Indicators of Behavior. The intensive education methods used in this study did not provide the expected results. Future watershed studies should include social scientists to better understand the role of humans in a watershed.

Testing of Soils. Some soil testing was performed as part of this study, however, a more intensive soil testing effort would provide valuable information on the fate and transport of pollutants.

Economics of LID. Economists should be involved in LID watershed studies to appropriately assess LID costs and benefits compared to traditional development.

Myths Refuted

Winter Infiltration. Although no formal seasonal analysis was performed to investigate BMP performance during winter months, paired watershed analysis of the LID subdivision indicated decreases in the runoff volume and rate as compared to pre-development. In addition, field observations indicated that the rain gardens, the grassed swales and the paver road functioned as designed through the winter months.

Frost Heaving of Pavers. Frequent concerns are voiced about paver blocks heaving in the winter due to frost penetration. The EcoStone® paver roadway has remained in excellent condition, with no frost heaving noted. The installation of a proper bedding material and storage layer to encourage rapid infiltration into the subgrade is critical to this function.

Education. Typically, intensive, one-on-one education methods are assumed to be the most effective means to bring about changes in attitude and behavior. However, on this project, this method did not bring about the desired behavior changes.

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