Eastbank Terrace Oct 2007 sewer-line replacement harms habitat

Laura Mol, steward, Dennis-Windham section [8L]
October-December 2007

Summary

In October 2007, this ecologically interesting habitat was torn up in the replacement of a leaking sewage pipe in the streambed curving around the Terrace. Issues are:

• What damage might have been averted if different procedures or standards had been in place or complied with? Why was M-NCPPC Natural Resources not consulted before the contractor concluded the project with turf-grass seeding?
• Could establishment of different processes prevent similar habitat damage during pipe repair/replacement projects that will occur along Sligo Creek in the future? Can Friends of Sligo Creek be of help in pressing for change in ecologically inadequate and damaging work done within the Park?
• What restoration work, if any, should now be done on the Eastbank Terrace?

Chronology

• Sept 29, 2007—Volunteers at the fall Sweep-the-Creek [the annual all-creek litter clean-up] notified section organizer Jane Barrett of smell and of a break in the pipe visible in streambed below Whitehall bridge; she reported the problem to the Parks off-hours/emergency phone number.
• Parks staff communicated information to the Washington Suburban Sanitary Commission, the public utility responsible for repair of sewer lines. WSSC contracted with one company to run a bypass, temporary line during the work on the cracked sewer line; and they contracted with a second company, Orbit Construction, for the replacement of the broken pipeline itself.
• October 2, 2007—Public notification by WSSC, including electronic alert to Friends of Sligo Creek via Stormwater Committee chair Ed Murtagh, who forwarded it to the Sligo Friends listserv (130 recipients)
• A 140-foot long and 23-to-53-foot wide swath down the center of the Eastbank Terrace was completely cleared—an estimated 4,720 square feet–including removal of:
  • the entire south border, a hedgerow of young trees and shrubs
  • a field-grown and fully mature spicebush (magnificent and unique, grown under full sun of open field rather than within the understory of the nearby fully canopied woods, as is the place of spicebush in all the rest of Sligo)
  • a tuliptree, in 2006 already over 10 feet in height, and
  • some sub-canopy trees on the western edge, particularly including black locust
  • Some additional damage was done by unintended "backhoe pruning." At the southeast corner of the Terrace, which has been a small oasis of all-natives, the corner Virginia pine lost 7 branches (diameter range: 1 1/4 to 2 1/2 inches), "pruned" by the passing machinery, and so now more likely to experience edge invasion by non-natives. The work was done by Orbit Construction, using a 23-ton hydraulic excavator (a Caterpillar 320C) and a much smaller utility crawler (a Komatsu SK-1020, estimated 4-5 ton). The Cat bore the company motto: Orbit Construction/ Digging for Dollars since 1978.
• The pipe in the stream channel was replaced, and the rip-rap repositioned along the east/south bank of the Creek at the breakpoint.
• Oct 10, 2007—Steward Laura Mol discovered the habitat damage and contacted Montgomery County Forest Ecologist Carole Bergmann and the Friends of Sligo Creek Stormwater chair Ed Murtagh
• Stormwater chair contacted WSSC community liaison Dawn Forsythe for further information
• Nov 2, 2007—Sligo Steward met on site with the M-NCPPC Forest Ecologist to survey the damage and discuss what restoration might be possible and desirable
• Nov 29, 2007—Steward asked WSSC Community Outreach Manager for detail about what seeding had already been done, as well as questions about what actually had been done as part of the pipe replacement project.
• Dec 4, 2007—WSSC's Dawn Forsythe, replied by email:

      The seed that was used in the R/W area near the repair site is called a "Contractor's Mix," which is a blend of 78% annual rye grass and 19% perennial rye grass and was installed by Orbit. This mix was not used in the grassy access areas. Our specification calls for 100% annual rye grass for non-tidal wetlands and non-tidal wetland buffers, but it should not be a problem because native grasses will also grow. The site has stabilized.
      Orbit Construction replaced approximately 18 linear feet of 21" concrete sewer main with 24" ductile iron. This was due in part to material availability at the time of the emergency and to facilitate the upcoming armoring project. Excavating to replace the section of main was minimal, maybe 6", if that much. The pipe was only replaced in the stream channel. The rest of the sewer main was in great shape, upstream and downstream. Orbit used existing stone at the site and one tandem of Class II stone to armor the main until the upcoming armoring project takes place

• Dec 14, 2007—Steward Laura Mol asks for further clarification, including:
  1. About the grass seed composition:

     if it's possible for you to find out the species and varieties of the "Contractor's Mix," it might save some difficult identification later--details of grass ID are very tough to figure out (small, small parts). As you may have been told, the terrace where the machines went through is an area that has been under natural history inventorying and observation since 2001....hence the desire for as much understanding as possible.

  2. What standards apply? When you mentioned "our specification," is that WSSC standards, or M-NCPPC's, or something else?
  3. Did I understand you correctly: that there was no digging along the length of the terrace, but only down into the stream channel?
  4. What's the "upcoming armoring project"?
  We sure don't want to be reforesting through there if there is more work planned. Will this terrace always be an access alley to the pipeline?.
• Dec 20, 2007—WSSC's Dawn Forsythe replied:
  On your question #1,

  I've attached a copy of the label from the contractor's seed [excerpt below]:
  Contractor's Mixture, contains: Annual Ryegrass, variety not stated, origin OR, 78% pure seed, 90% germination; Perennial Ryegrass, variety not stated, origin NZ, 19% pure seed, 85% germination; Other crop seed, 2% (no "undesirable grass seed"); Weed seeds, 0.12%.

  On your question #2,

  we are referring to WSSC Standard Specification 02920, found here: www.wsscwater.com/dsg-PERMITS/sect_2007_spec.cfm

  On question #3:

  There was no digging along the terrace. When the damaged pipe was removed, we visually inspected the line in both directions before the new pipe was installed. Since this was an SSO, the inside of the line was inspected by close circuit TV nine days after the event. We found several leaking joints that had light mineral deposits, so the line has been recommended for grouting.

  On question #4:

  We have preliminarily identified roughly 80 locations where our sewer pipe along (with some water mains) have varying degrees of exposure, some more severe than others. This site is included in that assessment. We are currently evaluating and prioritizing these sites for a possible repair contract. We will also be looking for opportunities to perform other sewer rehab while we have the access. We prefer to use trenchless methods to rehab the sewer pipe. We will work closely with MDE, M-NCPPC and others. Access to these sites will be required by track excavator and other heavy equipment.

  WSSC will be glad to brief Friends of Sligo Creek once we have a proposal for a comprehensive plan. But you should operate under the assumption that we will likely be doing some heavy work in that area again.

How the Eastbank Terrace looked on December 1, 2007

Also lost is the sense of unique place that had existed when the open old-field was fully surrounded by hedgerow, riparian buffer and woodlands. However narrow each of these sub-ecosystems was–5 yards or 20, variously–there was a visual definition as well as variety to the space. With the south hedgerow plowed out and the center graded level, the area has become an extension of the turf surrounding the tennis courts. It looks like a pleasant corner of recreational parkland, not like the interesting habitat that it had been.

As December begins on the Eastbank Terrace (in this strange, drought-distorted season), the new and incongruous green of sprouting turfgrass is being covered over and the rawness of the scraped-flat earth is softened by the textured yellow-browns of finally-fallen tuliptree leaves. The familiar sound of the resident piliated woodpecker can still be heard of a morning or late afternoon. The pipeline disturbance of October 2007–troubling as it is, and as immediately damaging–will become another in the long series of disturbances to parkland in the midst of intense human habitation. But can we protect it with more skill? Can we humans figure out how to do less damage to habitats of value to other species, as well as ourselves?

23-ton machine at south end of Terrace after clearing

More Photos