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The Peiyang Campus
A Sponge City Case Study

by Zou Pingxiu, Tianjin University; Lei Cao, Tianjin University; Jean Marie Hartman, Rutgers University

The Peiyang Campus

The "Campus Core" area, or the central courtyard, is a landscaped gathering space that captures and directs stormwater to the wetland area at the west of campus.

Like many older cities around the globe, China's largest cities face problems with stormwater management and flooding. Retrofitting older cities can be especially challenging because the upgrading of infrastructure often needs to occur below active streets and buildings. As China has begun to build new cities, many Western practices are being tested and incorporated; the ambitious designing and building of new cities creates opportunities for developing new and better stormwater systems.

"Sponge Cities," as used in Chinese literature, provide examples of adaptation of low impact development with a strong emphasis on stormwater management. In 2003, the concept of "sponge" appeared for the first time in the book titled "The Road to Urban Landscape: Communicating with the Mayor" (Yu 2003). In this book, "sponge" is a metaphor for the function of natural wetlands, especially as they relate to rivers, floods, and drought disaster control in cities. Natural wetlands have been largely disturbed or eliminated around older cities, so this means there is a need for restoration or re-creation of wetlands that can act as sponges for floods and excess nutrients. This is particularly important in moist to wet regions of China, where the majority of rainfall occurs in a few summer months.

In October 2014, the Chinese Ministry of Housing and Urban-Rural Development officially released "The Guidelines for Construction of a Sponge City - Construction of Low Impact Rainwater System" and officially put forward the concept of a Sponge City. From the end of 2014 to early 2015 the country elected to produce the first batch of 16 sponge pilot cities and now China's Sponge City construction pilot work is in full swing.

The Peiyang Campus

The water management system for the Peiyang Campus is divided into three drainage divisions, which are each further divided into two sub-drainage divisions. Within the central sub-basin, water is collected and reused for the landscape. The next ring outward collects run-off from the central basin and stores it in waterways and soil with potential for landscape application in a drought. This ring then connects to the outer ring through overflow sites, like rivers and lakes. Finally, the outer ring reduces stormwater pressure through release into natural systems.

Aspects of a Sponge City
A Sponge City's construction mainly includes three aspects: First is to protect the original ecosystem; the second is to restore and repair the damaged water body and other natural environments; the third is to use low-impact development measures to build the urban ecological environment.

Sponge City design indicates development and progress of urban stormwater management theory. It creates an ecological city, primarily focused on stormwater management ideas and approaches. There is a clear emphasis on a city's resilience to natural hydrological hazards through low-impact integrated management of urban stormwater.

The Peiyang Campus

Illustrative details of the campus design and water system integration show the direction of flow of rainwater (blue arrows) to the canals and lake that surround the campus. Also, note the (orange) circulation pump site that moves rainwater circulating around the campus and sewage to the treatment wetland site for purification. v

Site Remediation and Enhancement
The site that received Sponge City remediation was Haihe Education Park, where the campus site of Peiyang University is located in Tianjin. The site is characterized by shallow groundwater and saline soil with a high pH. Agricultural fields have been transformed into 1.55 km2 of buildings, 0.15 km2 of water and 0.8 km2 of restored and designed landscape. The landscape is divided into three sub-drainage systems to handle stormwater. The sub-basin that forms an outer ring infiltrates stormwater to groundwater, with minimal excess going to the adjacent canal or river.

Found in the inner ring of the campus, there is an integration of green infrastructure within the overall landscape elements through use of concave green spaces, pervious pavers, bioswales, and green roofs. This drops the runoff coefficient for the built-up area from 0.9 to 0.5, greatly reducing the likelihood of overflow from the site to the rivers. In this area, there are also water features, such as ponds and wetlands, that collect overflow, and thereby reinforce the sponge-like function of the area. The outer ring is referred to as the natural drainage area. The reforestation of the edge extends around most of the triangular site. This area functions both as a buffer and a release valve since excess water will be pumped out of the canals to the adjacent rivers to avoid flooding in the core area.

The Peiyang Campus

Forests and wetlands create a buffer between the canals and campus core, and bioswales are distributed throughout the 620-acre campus. Detention basins and treatment wetlands collect and filter stormwater as it passes from the main campus grounds to the inner ring lake.

In summary, the core area retains and infiltrates water through green infrastructure including bioswales, detention basins, rain gardens and a treatment wetland. Excess water is stored in the purification wetland and storage lake. Water from these sources can be pumped back to the campus when needed for landscape plants during a drought. When there is excess water in the purification wetland and storage lake, it is pumped into the canal that forms the outer ring. If there is excess water in the canal, it is pumped into the adjacent rivers.

Application of Low Impact Design (LID) Principles
The design of the 2.5 km2 campus is dense when considering the footprint of the buildings and the size of the population that will work and live there. However, the campus is designed to work as a high-functioning watershed and manages the majority of its stormwater on-site, as well as managing its sewer system on-site. The landscapes around the buildings and the buildings themselves are designed using LID elements such as landscape design, green infrastructure, and water management practices.

The Peiyang Campus

This picture shows landscaped gathering spaces that capture and direct stormwater to the wetland area at the west of campus.

Discussion and Conclusions
Peiyang Campus is one of the first examples of application of the Sponge City model to be built in China. The site for the campus had little urban infrastructure, so the stormwater, drinking water and sewer systems could be designed to manage all water on site without the expense of removing or updating low functioning systems. The site engineering could be designed and installed before buildings were added. Vegetation could be placed in clean, fresh soil that replaced initial saline soil. The plantings are flourishing on the clean soil and with the water management systems.

The campus has been occupied for two years now and is hailed as a success by its residents. There has been one major storm, 7/20/2016, that flooded many streets of Tianjin, while water failed to collect on the Peiyang Campus walkways and streets. This kind of success is promising for the ongoing adoption of this planning and design theory for the construction of new urban centers in China and around the world.

As seen in LASN magazine, June 2019.

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August 19, 2019, 10:33 am PDT

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