TEAM 07184 DESIGN CONCEPT This one-mile stretch of roadway has a lot to live up to. Currently, it is a two-lane asphalt road with no medians, which separates one of Texas History’s most sacred sites from a vast expanse of oil and gas industrial plants. Moreover, the need for smart stormwater management is ever present due to the close proximity to the Houston Ship Channel. LID, or Low Impact Design, methods are a viable means to achieve several goals pertaining to constraints of the site described above. In order to create a roadway that fits the definition of LID and meets the criteria set forth by Harris County Precinct 2, three goals are established. These goals are (1) enhancing environmental quality, (2) creating economically sound solutions, and (3) providing a unique experience for all users to enjoy. Our design concept includes a close approximation of nature while incorporating elements of Texas History, including the future historical status of Harris County’s first LID Roadway. Our first task in determining a typical cross section and drainage concept was to identify the existing resources within the 120-foot road right-of-way. The existing roadway consists of 2 lanes of concrete pavement with an asphalt overlay that included 10-foot shoulders. The resources available for re-use include crushed concrete, milled asphalt, oak trees, and rain water. There are also elements of Texas History along the route which can be addressed during final design. In a natural, undisturbed-by-man condition, this area would be coastal prairie characterized by vaguely defined drainage basins with highpoints outlining the edges of the basins and low points in the center. Some basins would be interconnected by low points or overflows from one basin to another. The prairie condition would be maintained by periodic fires from natural causes, primarily lightening strikes and drought. Our concept is to mimic the natural conditions as closely as possible while maintaining public safety and reducing the cost of road re-construction. The requested road features are 4 lanes of 10-inch concrete pavement with a center median contained within a 120-foot right-of-way. No offsite drainage is to be considered in the conceptual design. A hike and bike path was discussed as a positive feature as well as a Project Stars feature at the intersection with Tidal Road. To accomplish this we divided the road right-of-way into small drainage basins based on the required median openings for cross traffic and a maximum length of 600 feet. The concrete pavement is sloped to drain to a 40 foot center median and curbed on the outside. The median is designed to detain, filter, and convey rainwater to the outfall point at the south end of the project. The detention is accomplished above the surface in the depressed median. The water is slowed to allow for infiltration into sequenced bioretention cells with gabion level spreaders filled with crushed concrete from the existing roadway. A variety of drought tolerant plant species that are also documented in the pollutant uptake ability populate the bioretention swales. Filtered water conveyance is provided through a slotted HDPE pipe at the center of the bioretention cells and below the engineered soil mix which also provides filtration. A pervious concrete hike and bike path is included on the east side of the roadway, which could connect to a similar system within the San Jacinto Battleground State Park.
SITE PLANS Independence Parkway - South Independence Parkway - North STATE OF TEXAS VISTA TIDAL ROAD RAIN FOR RENT VOPAK TERMINAL DEER PARK VOPAK TERMINAL DEER PARK UWOOD PROJEC T STARS PLAZA WILLIAMS BROTHERS CONSTRUCTION TEXAS PARKS AND WILDLIFE TEXAS MOLECULAR LLC
LANDSCAPE PLANS TYPICAL ROAD CROSS SECTION BIORETENTION MEDIAN SECTION BIORETENTION MEDIAN PLAN BASIN PLANTING LEVEL SPREADING GABION GRASSPAVE2 SHOULDER SIDE SLOPE PLANTING 6’ BIKE TRAIL SHADE TREE 6’ GRASSPAVE2 SHOULDER 25’ CONC. PVMT 6’ BIKE TRAIL 28’ BIORETENTION AREA ENGINEERED SOIL SLOTTED HDPE PIPE
LANDSCAPE PLANS PROJECT STARS PARK PLAN TRAILHEAD MONUMENT BIORETENTION CELLS WITH LEVEL SPREADING GABIONS PARK/DISTRICT SIGNAGE PROJECT STARS PLAZA BIOSWALE PROJECT STARS PLAZA INFORMATIONAL SIGNAGE, HISTORIC FLAGS, AND PLANTING. PLAZA RAISED FOR VIEWING OF SAN JACINTO MONUMENT. BIOSWALE W/NATIVE PLANTS BENCH NATIVE SHADE TREE TRAILHEAD MONUMENT HISTORICAL MONUMENT TRAILHEAD MONUMENT
IRRIGATION/ RAINWATER HARVESTING PLANS Rainwater Harvesting was considered for the design of this project. However, the low impact design for the roadway does not require a longterm water supply for irrigation. Therefore, rainwater harvesting is not necessary for the roadway. If rainwater harvesting were necessary, this team would propose an underground rainwater storage system with a renewable energy pumping system to deliver the water to the end user. The renewable energy source proposed by the team is solar. However, we identified two potential users of harvested rainwater along the project route, one is a public entity and the other is private.
IDENTIFICATION AND JUSTIFICATION OF HYDROLOGIC/DRAINAGE MODEL UTILIZED Existing Conditions The parameters provided for use in the SCS method were rainfall depth, average velocity for the flow path, curve number and drainage area. Using this information, the existing conditions hydrographs were reproduced as closely as possible. No offsite flow was considered. Proposed Conditions The proposed roadway increases the paved area by approximately 5-feet along the length of the project, includes nine median crossings and a perviously paved walkway. The resulting increase is approximately 1.75 acres, half an acre of which is the pervious walkway. The roadway will be an inverted crown, draining toward the median. The medians will be depressed, with vegetated swales draining toward a low lying basin. The basin will drain through a layer of engineered infiltration soil into 36-inch slotted HDPE pipe, which will convey the stormwater to the outfall. The length of the roadway was divided into nine drainage areas. Proposed hydrographs for each area, based on the improved land use, were created using the SCS method. The proposed hydrographs were imported to a dynamic model, ICPR, for attenuation and routing. It is a cost effective way to accurately route hydrographs. The detention provided is approximately 1.2 acre feet per acre of increased impervious area. The ponds effectively attenuate the runoff for all three design events, while still allowing a passable lane during the 100-year event.
PROJECT COST ESTIMATES AND COMPARISON TO THE PROJECT COSTS IF TRADITIONALLY DEVELOPED Right-click the Excel Icon, then choose “Open Hyperlink” A cost analysis was prepared, comparing construction costs and future maintenance costs for both designs, Green and Traditional. The construction cost estimate is $5,090,387 for Green design and $5,004,754 for Traditional design. However, maintenance costs are lower with the Green design, so a savings will be realized that will offset the additional construction cost approximately 11 years after the project is completed. The detailed cost estimates and comparison may be viewed below.