South River City Citizens
Blunn
Creek Erosion
February 6, 2004
11am meeting: Sherri Ancipink, Morgan Byars, Bob Drew, Jean Drew, Mike Kelly, Jeff Kessel, Tim Mahoney, Karen Marks, Alicia Rinemund, Ginny Rohlich, David Todd and Ken Zarker met at 709 East Monroe at 11am on February 6, 2004, to review watershed maps and erosion photos of the Blunn Creek, and to visit the Creek.
Park paths: The group started towards the north end of the creek, looking first at the erosion underneath the concrete walk, on the west side of Blunn, as it passes under the East Monroe Street bridge. The walk has been replaced three times in 20 years, and is again heavily undercut. Bob Drew believes that it was thoroughly shored up the last time it was replaced.
Springs and baseflow: As we were walking by the baseball park, there was discussion about the old swimming hole that used to be there, fed by springs. Evidently a child died while swimming there in the 1930s, and the springs were plugged and the swimming hole closed. There was a proposal to open the springs and perhaps help restore the baseflow of the creek, helping the trees along the stream, and the fish and frogs and other life in the stream itself.
Road closures: We next visited the bluff to the west of the Little Stacy park. Mike Kelly and Morgan Byars think it is too steep to shore up as is, and that a 2 1/2 - 3 to 1 slope is needed in order to protect this bluff, and guard against erosion of presently intact banks upstream and downstream. The extra horizontal space might be available if East Side Road were closed and replaced with a narrower path and a "low impact development" (LID) planted swale. Such a swale might also help restore the base-flow to the Creek. The closure of East Side would likely extend from the alley (parallel with and to the west of Alameda, running east of the Little Stacy tennis courts) to the park pavilion, according to Jean Drew. The Fire Department and EMS have signed off on the closure, provided that a T-head or cul de sac is provided near the East Side bridge and the park pavilion. The city traffic division would be pleased to see the road's closure, in part because of the hazardous poles and stones along the creek-frontage of East Side. To make such a closure happen, though, the SRCC will need to organize a petition for closure, and will need to address providing enough parking for park visitors (maybe near the volleyball court), and access for park maintenance (perhaps the trail could be wide enough for a park vehicle to pass).
Groundcover: Bob Drew pointed out the ravine-like erosion and mud washed down from the park near the north end of the alley that runs parallel and west of Alameda. He thought that there needed to be more groundcover in the park, and wondered if this might be something that SRCC members could help with - spreading grass seed or otherwise. Morgan recommended removing the curb (and curb cuts) which he saw as the primary cause for the concentrated flow causing the gullies.
Smaller measures: Next, we looked at erosion on the north side of Sunset, west of Alameda. Ken Zarker mentioned that Sierra Club and SRCC members had installed juniper logs to and plantings in this segment within the last two years to retain creek bank soil, but the juniper logs were being used as steps now, and the plantings had largely been swept away. The plantings might have had a better chance of surviving if a reliable source of water were nearby throughout the summer. Mike Kelly felt that it was OK that the logs were being used as steps, since the logs appear to be holding the bank and there needs to be good creek access anyway. Mike seemed to give a lot of credit to using the small measures, and not just relying on large, costly projects.
Larger projects: A conversation about the erosion on the west bank of Blunn, between Monroe and Woodland, immediately east of East Side Drive, followed. A complete retaining structure, such as boulders piled from the toe of the bank all the way to the top, would be costly, perhaps $45/square foot or $100,000. Or, if there were horizontal room to peel the bank back to a 2 1/2 (horizontal) - to - 1 (vertical) slope, and the new more gradual bank slope were only reinforced with boulders at the toe, and a soil retention blanket and vegetation for the rest of the slope, the cost might be halved. It could be cheaper if done in-house (there's more experience and less oversight with a City crew, and no profit), but there is only one erosion crew and supervising engineer for the City. Incidentally, Morgan Byars mentioned that the City staff have long asked for adding an additional erosion crew, which was also recommended in the Master Plan. He thought that this might be an option for SRCC to lobby for: the initial capital cost would be on the order of $500k to $1M for the equipment (a track loader and excavator), and $300k/year for a crew of five.
Scour hole: We next looked at the "scour hole" roughly 100 feet north of the Woodland bridge. Jeff Kessel and Mike Kelly discussed ways to stabilize it, perhaps shoring up the west edge with boulders, smaller stones, erosion sheeting, and vegetation, and leaving the east edge as is. There appears to be relatively little risk of this pool expanding a great deal, since it is in a straight stretch of the creek, unlike the cliffs at bends and corners in the creek.
Wastewater lines: Mike Kelly discussed the recent EPA administrative order, which requires the City to eliminate unpermitted wastewater discharges from leaking sewer lines by 2007. Many of the leaks come from pipes that were laid within the creeks years ago but are now broken and cracked (fortunately, the current city policy is to lay lines outside the Critical Water Quality Zone, at least 50-400 feet from creeks). These pipes are concrete, clay, or a WWII-era combination of asphalt and cardboard, and often need repairs or realignments. The City is attempting to coordinate repairs to the lines with erosion control work, which might affect work in the Blunn Creek basin, where there are both leaking lines and erosion problems.
Detention and infiltration: As we walked along the creek, Morgan Byars discussed the importance of limiting the impacts of upstream development, particularly by capturing the runoff from "2-year storms " (ones with a 50% chance of occurring in any given year - 2.6 inches of rain in 3 hours) in detention basins. The current understanding is that it is important to let this runoff infiltrate, and trickle slowly out to the surface as the Creek's baseflow. Mr. Byars praised the SRCC work on reducing runoff from the Home Depot, Wal Mart and Galaxie sites as good examples of this kind of effort.
Master plan priorities and erosion work: This kind of upstream detention seems especially important given the low likelihood of immediate attention to the downstream erosion. Mr. Byars emphasized that, as serious as Blunn's erosion problems appeared to us, they were rated relatively low on a city-wide basis in the Master Plan, and funding is tight even for highly ranked sites (typically where private residences are threatened by erosion). Blunn's reach #3, between Oltorf and Woodland, is ranked 26th among 200 Austin stream segments, and still would likely not be worked on for 10 years. The 1997 Master Plan identified $800 million in stormwater management need (including $120 million for erosion control, and the balance for flood control and water quality work), but the current capital budget only allows $1 to 2 million to be spent on erosion each year. Erosion on Little Walnut, Walnut, West Bouldin, Boggy, Onion, Williamson, and Fort Branch is ranked higher than Blunn, and is slated to get attention earlier than Blunn. Though released just 3 years ago, the Master Plan is based on erosion studies back in 1997, and might be out-of-date in some respects. Fortunately, the Plan is supposed to be a "living document" that can include accelerating changes such as what many of us are seeing on Blunn. However, City staff are reluctant to revise rankings for any single Creek without revisiting all the City creeks, which is unlikely to happen in the next 5 years.
Rain and erosion: There was some discussion of whether the recent erosion on Blunn was due to increased impervious cover in our basin, or if that was unlikely since so much of it is built out. Morgan Byars said that many Austin creeks were suffering from the torrential 1998 and 2001 storms that dropped 7 and 6 inches respectively in just 2 days.
Hard vs. soft solutions: We next looked at erosion along the east side of Blunn, abutting Sunset Drive, where a steep cliff is appearing, threatening the street and adjoining trees. Here there was discussion about the choice between a hard and steep "armoring" of the bank, or the cheaper, more natural-appearing and sustainable, option of tapering the bank to an angle of repose (somewhere around 2 1/2 to 3: 1). Peeling the bank back to such a gradual slope would require closing or greatly narrowing Sunset, though. It is unclear if adequate support for closure could be found among the homeowners who front on Alameda but back up to Sunset.
Water quality: Ginny Rohlich explained that the City is considering a consultant's proposal to do just this sort of grading of the creek bank, though farther upstream on the Creek, between Fairmount and Travis Heights Elementary School (slightly north of Mariposa). The proposal involves stripping the pavement from the closed portion of Sunset, along with removing the asphalt on the currently open loop next to the wooden bridge. Next, the City would install a crushed granite path, maybe 6-8' wide, next to the Creek, and parallel to that, a vegetated swale. The goal is to remove some of the suspended solids that come into the creek from surface runoff. This would be similar to what the City is suggesting for the segment of the road fringing Little Stacy park, though here, in addition, the City is also considering installing a detention basin, without concrete walls, in the triangle of park land at Fairmount and Sunset.
Complications: The City has budgeted money for the Fairmount-to-Mariposa project that Ginny described, but the consultant's bid is too high (in the million-dollar range), and will need to be reconsidered to see if the amount of suspended solids removed / dollar spent can be improved. Another consideration is whether there will be adequate support for closure of the Sunset road loop next to the wooden bridge: some parents drop their children off for school there. However, in preliminary visits, the principal has said she could support closure of the loop. Ginny Rohlich said that she'd be glad to make a presentation to SRCC on the proposal.
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2pm meeting: We met again to discuss the Creek at 2PM on February 6, 2004. Barrie Cullinan, Tim Mahoney, Jean Mather, Eileen Rovira, Ted Siff, David Todd and Betty Weed were present.
Long-term changes: To show the changes in the Creek over the years, there was a proposal to secure old photos or descriptions of Blunn Creek that we could compare against. SRCC residents might have some, but it could be worthwhile checking the Austin History Center, or looking through the 1976 book, "Creeks".
Middle basin: Much of the afternoon meeting's discussion concerned the sources of the runoff and causes of the erosion on Blunn that we saw earlier in the day. A good deal of the runoff seems to be coming now from the middle of the basin: above Oltorf but below Woodward. Betty Weed pointed out that there is a major stormwater line that enters the Creek at Oltorf; the Creek's flow seems to increase rapidly from south of Oltorf to immediately north of Oltorf.
Gardner-Betts Center: Development of the Gardner-Betts Juvenile Detention Center appears to have accelerated the runoff. It is unclear whether the swale on the west side of the Center (facing Congress) is meant to capture runoff to Blunn.
Parking lots: The broad areas of pavement in the Twin Oaks Shopping Center area, are both a problem and an opportunity. There's undoubtedly a good deal of runoff from the parking lot, but these lots, especially the underused ones (for instance between Beall's and the Bank of America building), could be a good place to put swales to collect and filter runoff.
St. Edward's University: Development of the St. Edward's campus also seems to be increasing downstream flows and erosion. Jeff Kessel's review criticized St. Edward's for its drainage design and off-site impacts. The campus zoning is quite permissive of high impervious cover, but numerous possible detention sites do exist, such as one near the St. Edward's tennis courts. Ted Siff recommended contacting the new president of St. Edward's. Elloa Matthews, who tracks activity at St. Edward's for SRCC, might also be a resource.
Road construction: Construction of the Ben White road is another concern, since much of the runoff in the area outside of the Barton Springs recharge zone is not captured, and in our section goes ultimately to Blunn Creek. Jean Mather mentioned that she was meeting with Mike Walker, an environmental representative for the Texas Department of Transportation, on March 8, to discuss runoff to Harper's Branch. Perhaps discussions regarding Blunn Creek could be added to that meeting.
AISD land: One possible area for mitigating runoff to Blunn involves the AISD 10.5-acre parcel near Payload Pass and Ben White. Most of the site is undeveloped. There is only a single warehouse existing on the parcel, near the northwest corner of the site, a good distance from the east edge of the parcel which tracks Blunn Creek. Matt Hollon has said that this parcel would provide an excellent Blunn Creek detention basin site, and understood that there were no immediate plans for this parcel at AISD. Perhaps AISD would be willing to entertain the idea if there were some outdoor laboratory function for the parcel. Tim Mahoney emphasized how valuable Blunn can and could be as a biological field site for Travis Heights Elementary and High School, as well as St. Edward's. Jean Mather thought that AISD trustees Fitzpatrick, Whiteside and Montoya could be good contacts to discuss possible options.
Possible action items (in no particular order):
Minutes prepared 2/11/04 by David Todd (416-0400), dtodd@wt.org
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