Clear Lake City Water AuthorityPresentation to Space Center RotaryJuly 14, 2008

CLCWA BackgroundCreated in 1963 by the state legislature at request of the developer to provide water, sewer and drainage service to an unincorporated area.Largest water district in TexasCovers 16,100 acres, most of which are now in the city of Houston, but also includes most of Taylor Lake Village and parts of Pasadena, Webster and La Porte.

Background Cont.17,910 water connectionsServes 17,423 homes; 47 completed multi-family complexes which include 10,726 apartments, townhouses, duplexes, and condominium units; 1,348 acres of commercial/industrial parks; and JSC through contract.2007 Taxable Assessed Valuation of $4.2 billionAnnual operating budget of $10 million

ServicesWater provide potable water service to the district; one of the first water districts to switch from ground water to surface water due to subsidence; currently contracted for up to 20.45 MGD of potable water through the southeast water treatment plant.

Services cont.Waste Water Treatment plant has the capacity to treat 10 MGDDrainage cities are responsible for the street drains; we are responsible from the street drain inlet to the county drainage ditch; and county is responsible for the drainage ditch through the bayou.Other authorization but not utilized contract for law enforcement, and park/recreation operation

Progressive and Pro-active ActionsConsistent Superior water quality rating from state24 hr emergency responseOne of lowest water/sewer/tax rates in Harris and Galveston countiesRecycled water facilities at golf courses and UofH/CLSponsor water conservation program in CCISD elementary schoolsOne of the few government bodies which allows open comments from the floor at the beginning of every board meeting and before any votes are taken on agenda items

Actions cont.One of first governments in Texas to establish a continuous infrastructure rehab program to ensure long term reliabilityProvide adequate fresh surface water capacity at lowest cost to meet future needsControl over increased flooding through realistic storm water detention requirements for new development based on local rainfall, elevation, soil type, etc. and not county averages.

Current Hot ButtonFlood Control

What Is a 100/500 Year Event?The use of 100-year and 500-year event terms are somewhat misleading.A 100-year event equates to 13.5 inches of rain within a 24 hour period.A 500-year event equates to 19 inches of rain within a 24 hour period. (19.33 in Allison 02)Markings on the TSARP map only show those areas contiguous to a waterway and does not include depressions (ponding) which are non-contiguous.

TSARP 100 & 500 Year Flood Zone Horsepen Bayou B104-03-00B104-02-00Horsepen BayouLawrence G. Dunbar, P.E. July, 2005

Flooded Areas Along Reseda Road Lawrence G. Dunbar, P.E. July, 2005

CURRENT FLOODINGThis is a photoof a home backing up to the golf course next to the club house and a car in the street. The photo was taken after the water had somewhat subsided, by the home owner who has had water in his house three times and estimated 44 inches of water in the street during that one specific rain event. In addition to the Reseda area, significant other flooding has been recorded in several other areas as illustrated on the map.

ApproachHired hydrology consultant to better understand flooding in our specific watershed and make recommendations on how to mitigate any future increase and reduce existing problems if possible.LearningsFlooding is a result of storm water run-off.Detention is now becoming recognized as the best method to control flooding along the Texas Gulf Coast versus previous emphasis to make drainage waterways wider, deeper and straighter.Harris County Flood Control District developed their detention requirements several decades ago based on the average county rainfall, soil types, elevations, etc. The Clear Lake area is significantly different in all these conditions than Northwest Harris County. HCFCD currently has their detention criteria under review.

Quote From Golf Course Development Impact StudyAs one would expect, peak flow rates within these ditches resulting from this proposed development would increase considerably from those computed for existing conditions. Even though these ditches have capacity to handle additional flow before reaching their banks, any increase in water levels within these ditches would adversely impact the local storm drainage system that is connected to these ditches. Also, any increase in flow rates entering Horsepen Bayou from these ditches would aggravate the flooding along Horsepen Bayou.

RecommendationsDevelop a detention criteria based on specific conditions within our watershed. The 1 acre foot per acre requirement is not any more restrictive than policies put into place in Fort Bend and Brazoria Counties.Acquire additional land at headwaters of Horsepen Bayou (end of runway at EFD) for detention ponds.Acquire the available 178 acres in OB/OBW (former golf club) to retro-fit the older developed areas with detention

OB/OBW Area Detention Pond178 acres available for detention pond1,727 acre feet of storage capacity available at elevation of 17 feet (assuming 20 ft maintenance berms, 3:1 side slopes, and an average depth of 11 feet)2,047 acres would drain into the pondsPeak discharge entering Horsepen Bayou for 100-year flood event would be reduced from approx. 3,000 cubic feet per second down to 300 cfs.Reduces 100-year flood levels in Horsepen Bayou downstream of El Dorado Blvd. by 20% or the equivalent of around 1.5 feet.

EFD Area Detention PondAcquire around 170 acres for detention ponds2,000 acre feet of storage capacity available at elevation of 22 to 24 feet.4,365 acres would drain into the pondsPeak discharge along Horsepen Bayou at ponds for 100 year flood event would be reduced from approx. 5,000 cfs to 3,000 cfsReduces 100 year peak flows in Horsepen Bayou downstream of Space Center Blvd. by approx. 2,000 to 3,000 cfs (around 40%)Reduces 100 year flood levels in Horsepen Bayou downstream of Space Center Blvd. by approx. 4 feet.

Combined Detention PondsReduces peak discharges along Horsepen Bayou for 100 year event by 2,000 to 5,000 cfsReduces maximum flood levels along Horsepen Bayou for 100 year event by 2 to 4 feetReduces peak discharges in Armand Bayou for the 100 year event by approx. 4,500 cfs (around 15%)Virtually shrinks the 500 year event floodplain down to the existing 100 year event floodplain level

Multi-use For Taxpayer ValueSingle use does not maximize taxpayer valueDetention pond areas can be used for a wide variety of recreational activitiesPledge to work jointly with County, City and local citizens to develop a plan for designing multi-use amenities into the detention facilities

Status of RecommendationsNew storm water detention policy put into place in Nov. 2005 which applies to all new developmentGolf course condemnation court hearing reset to begin the first week of Sept. 2008. Motion for Summary Judgment on validity of deed restrictions was upheld at a hearing on April 24, 2008EFD area ponds have been discussed with HCFCD and City of Houston. Since development in that area is not eminent, concentration of efforts is centered on the OB/OBW property at this time. Will take the cooperation of Exxon Mobil, Harris County, and City of Houston to put into place.

What You Can DoContinue to bring up the flooding issue to every level of elected officials CLCWA, city, county, state, and federalRemember that the elevation increases to the west as they increase storm water run-off, where do you think it drains? All area governments need to work together.

Thank YouFor the opportunity to serve you and to explain how the CLCWA impacts the quality of life in the Clear Lake area