Enhance Environmental Integrity of the Corridor
Like many cities, increasing air and water pollution, urban heat island effects, and invasive plant species affect the environment of Downtown Lincoln. Currently, the P Street Corridor contains almost 92% impervious surfaces that carry pollutants to regional water sources. By employing the strategies and tools listed in this Master Plan, the Corridor can improve its environmental quality and create positive changes in the regional environment.
STRATEGY 1: Increase Tree Health
An inventory taken by the Nebraska Forest Service has shown that Nebraska has lost approximately half of its community tree resources since the late 1970s. Many trees in Lincoln have been the victims of natural disasters, Dutch elm disease and pine wilt disease. Tree health and the urban canopy plays a vital role in the environmental health of the Corridor and the Region.
The Master plan includes the removal of unhealthy trees. 38 of the existing healthy honeylocust trees will be salvaged, reducing the amount of plant waste. These trees will supplement the 519 new trees that will be added to the Corridor’s streetscape. Using silva cells and suspended paving, current soil volumes of 120 cu/ft will be increased over 400% to reach ideal soil volumes.
STRATEGY 2: Increase Permeable Surfaces
Within the P Street District, 91.8% of the surface area is impervious, meaning water that is not absorbed into the ground is directed to flow away from the District, picking up pollutants and sediment on its way to the closest water source or collection site. The P Street design has over a 2x increase in the amount of permeable surfaces using permeable paving and increasing the amount of softscape reducing the number to 82% impervious surface by adding 107,004 sq/ft of pervious material.
STRATEGY 3: Total Capture of the 90% P Storm
Downtown urban environments, like Downtown Lincoln, can generate significant amounts of surface water runoff. Runoff is associated with increased erosion and flooding, water quality degradation, loss of biodiversity and aquifer depletion. Within the P Street Corridor, 91.8% of the surface area is impervious and all run-off is removed from site using conventional storm drains, meaning water is not absorbed into the ground but is directed to flow away from the Corridor, picking up pollutants and sediment on its way to the closest water source or collection site. The P Street District design captures and treats at a minimum a 1.24”, 24 hour storm event which represents 90% of all rain events in Lincoln. This is referred to as the “P Storm.”
Using rain gardens, suspended pavement, and permeable paving, the P Street Corridor will be able to effectively cleanse, diffuse and absorb water 90% of all run-off on site, feeding the plants within the Corridor and improving overall water quality. In addition to the on-site benefits of this design, the resultant reduction in stormwater runoff volume will protect and enhance regional aquatic systems and reduce the cost associated with storm drain reconstruction
STRATEGY 4: Use Native, Non-Invasive Plants
100% of the plants recommended for the P Street Corridor are native to the Nebraskan landscape. The use of native plants that are non-invasive and appropriate for site conditions and climate will improve landscape performance and reduce resource use in the Corridor. Native plants use less water, less fertilizer and less maintenance.
STRATEGY 5: Salvage Healthy Trees
Most of the P Street Districts’ trees are growing in less than 200 cu/ft of soil. There are 46 healthy trees, mostly honey locust, growing along the district that have adequate soil volume to live. The street design integrated 38 of these trees into the new design by a series of best practices including a suspended wood decking system that will span over the uncompacted soil and allow for nutrient, water and air flow into and out of this existing soil. Where healthy existing trees could not be saved the design team replaced them with new trees planted in a minimum of 500 cu/ft of soil.
> The recommended design uses stormwater best management practices, rain gardens, and native vegetation to improve air and water quality of the Corridor. This benefit not only has positive effects on the Lincoln community, but these measures require less maintenance and serve to create a more sustainable P Street.
> The increased tree canopy and the addition of biorention rain gardens within the Corridor can lower energy costs for heating, cooling and water treatment and has the potential to increase annual property values.
> The stormwater management systems recommended in this design will help to improve the regional water quality and drinking water resources.
> Increased tree canopies, native plantings, and rain gardens are increasingly found to be important deterrents of crashes and injuries and contribute to a more comfortable and visually interesting environment for all users