Maryland State Highway Administration – Environmental Programs Division
- Wetland Mitigation Design- Creation, Restoration, Preservation and Enhancement
- Stream Restoration and Stabilization
- Habitat Creation
- Natural Resources Inventory & Evaluation
- Wetland Delineation & Functional Assessment
- Forest Stand Delineation and Forest Conservation Plan
- Environmental Permitting
- Riparian Reforestation
- Invasive Species Management
- Erosion and Sediment Control
Coastal Resources, Inc. (CRI) provided mitigation design services for the Maryland State Highway Administration’s (SHA) Intercounty Connector (ICC) Compensatory Mitigation site SC-19. CRI provided wetland creation, restoration and enhancement design, habitat creation, natural resource inventories, wetland delineations and functional assessments, forest stand delineations and forest conservation plan preparation, stream gage monitoring, geomorphic assessments, hydrologic and hydraulic analyses, stream restoration design, and environmental permitting. In addition, CRI provided the Designated Specialist and construction oversight.
The SC-19 project is a wetland mitigation, stream restoration, and riparian reforestation project located in Montgomery County within the Great Seneca Creek Watershed. SC-19 was identified by the SHA Environmental Programs Division to compensate for environmental impacts anticipated from construction of the ICC, and is a required component of the ICC Environmental Stewardship and Compensatory Mitigation (ESCM) package. The mitigation site is located west of Woodfield Road (MD 124) at the crossing of Great Seneca Creek just south of Watkins Road. The wetland creation area for the site is associated with the floodplain of Great Seneca Creek and connects to adjacent riparian forest and wetland habitats to the north and south which are owned by Montgomery County and the Maryland-National Capital Park and Planning Commission (M-NCPPC).
Preliminary restoration objectives identified for the SC-19 wetland site included creating wetlands and providing water quality treatment for agricultural lands (SHA, 2004). Goals for the SC-19 site included:
- the creation of 25.0 acres of Palustrine Forested (PFO) wetlands,
- enhancement of 0.44 acres of Palustrine Emergent (PEM) wetlands,
- preservation of 13.15 acres of PFO wetlands,
- preservation of 1.55 acres of PEM wetlands,
- 0.5 acres of riparian reforestation, and
- 8,154 feet of stream bank live staking.
Eighteen (18) groundwater monitoring wells were installed on site in 2007 by the GEC, and groundwater levels were monitored during the 2007 and 2008 growing seasons. In 2009, CRI continued site evaluation of SC-19, and obtained and reviewed all pertinent readily available existing data of the study area. CRI installed, maintained and evaluated water level data from groundwater monitoring wells, stream gages, and piezometers during the 2009 growing season. Hydrologic analyses including water budgets, along with wetland delineations and functional assessments, forest stand delineations, and forest conservation plans were completed. SHA temporarily lost access to the site in November 2009, but CRI resumed groundwater and stream data collection in May 2011 when SHA acquired the SC-19 study area. Detailed evaluations of microtopography and functional assessments of reference wetlands were conducted to inform the design approach. Geomorphic assessments and hydraulic analyses of the stream were conducted to determine flooding frequency for improved floodplain connectivity, and in order to stabilize meander bends where previously placed concrete is proposed to be removed from the stream.
The proposed wetlands were designed to be groundwater fed, with supplemental surface water inputs from increased overbank flooding of Great Seneca Creek and an unnamed tributary of Great Seneca Creek. SC-19 includes creation of 25.0 acres of forested wetlands that were designed to maximize wetland functions and floodplain connectivity. Anticipated functions for the created wetland based on functional assessments include: groundwater discharge/recharge, flood flow alteration, sediment/toxicant retention, nutrient removal, production export, wildlife habitat, and visual quality/aesthetics. In addition, the wetland creation grading will provide benefits to Great Seneca Creek including a) creating more frequent out of bank floods that will reduce sheer stress on the streambed and erodible banks, b) reducing stream bank surface area susceptible to erosion, c) bioengineering and vegetative stabilization of banks and riparian buffer. Vernal pools, Brush Piles, and Trunk & Bole Habitat structures were also designed as part of the created wetland to both maximize potential wildlife habitat and increase water quality treatment associated with out of bank flooding.
CRI prepared the Preliminary Investigation (30% design), Joint Permit Application, Semi Final (60% design), Final (90% design), and PS&E (100% design) submittals, and erosion and sediment control plans. CRI also acquired all environmental permits, and erosion and sediment control permits. Final Design Plans, Specifications, and Estimate for the wetland creation project SC-19 were completed in 2012. During construction, CRI provided the Designated Specialist to insure designs were properly implemented.