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Grapevine Creek-CS090802iw, August 2, 2009 Cindy Frie & Alex Baker 581 Rocky Branch Lane Coppell, TX 75019 GLENN TRACY, P.E. Consulting Engineer Re: Engineering Design & Consultation: Spread Footing Cast -In -Place Concrete Retaining Wall Construction GT Project 2007005 Dear Cindy & Alex: IX "NO01 On -site re- review of completed retaining wall construction was performed on July 24, 2009. The re- review was requested by you because of written claims by the City of Coppell that: • "...the new wall you built... created a change in the drainage pattern causing flooding in the upstream properties." • "...excess fill material was placed behind the wall at time of construction." • "...property owners in adjacent areas are being negatively affected... because... storm water is obstructed from draining properly." The City further requested that • "...you immediately restore the ground between your wall and the drainage easement to the level it was prior to construction of the wall." The on -site re- review meeting was attended by you both, and by Mike Garza, E.I.T. and Albert Samaniego, both representing the City of Coppell. Background Original retaining wall design and construction efforts were intended to replace an existing decayed crosstie retaining wall located in your back yard. Proposed constructions were to: • offset original wall alignments to increase usable back yard area. • raise wall heights to flatten the back yard's slope to improve back yard usability. Proposed wall geometry changes were understood to require importation of borrow fill. Multiple engineering construction reviews of retaining wall construction efforts had been performed during original construction. Construction reviews were originally provided as required for City of Coppell construction approval and as requested by you. Construction observations and associated Engineering Design & Consultation: August 2, 2009 Spread Footing Cast -In -Place Concrete Retaining Wall Construction 581 Rocky Branch Lane Coppell, TX 75019 GT Project 2007005 construction certification were provided in a letter to you dated November 29, 2007. Among other comments, the original certification letter stated: • "Completed retaining wall structures appeared to conform to the intent of the engineering design plans..." • "Overall wall geometry closely approximated alignments specified in the original engineering site layout." • "Wall heights matched proposed section dimensions." • "End of wall alignments matched existing grades. " Note: an additional hardcopy of the original certification letter was provided to Mike Garza, E.I.T. during the on -site re- review meeting. Select pictures from that letter are additionally included with augmented comments in this letter's appendix. Observations & Analysis Review of pictures from original construction efforts noted significant contractor (i.e. Alex Baker, et al) care to prevent off -site migration of excavated soils. Silt fence surrounding lower construction zones that faced the drainage channel was maintained for the duration of construction. This was not only to prevent contamination of the drainage channel, but equally importantly to reduce importation costs of borrow required to raise and level your back, yard. Picture review also noted that original toe grades were maintained with no fill placed and no increase of the channel level. Re- review of completed retaining wall construction observed well maintained lower yards and shared channel at yours and your opposite neighbor's lots. No additional fill was believed present below (i.e. at the toe face) of your wall. The north neighboring opposite lot to the especially appeared less well maintained with historically old flora growth and structure placement appearing to impede channel flow. Not unexpected sedimentation and debris collection were seen. Anecdotal pictures you provided further indicate improper debris and refuse disposal into the upstream channel and associated lesser maintenance efforts (e.g. slow debris removal) at upstream lots that trap debris. Summary Written claims by the City of Coppelll are not generally supported by engineering re- review of completed retaining wall construction. New retaining wall construction at the rear of your lot: • Does not appear to have changed historical drainage patterns in the channel. Poorer channel drainage appeared historically, old. Does not appear to have caused upstream flooding. Flooding in upstream properties appeared more likely caused by influences beyond your lot's influence (e.g. upstream retaining wall and fence construction in the primary channel, upstream poor channel maintenance, upstream disposal of improper debris into the channel). More likely, conscientious maintenance of yours and your opposite neighbor's shared channel and lower lot landscaping has prevented even worse upstream flooding. 2 Engineering Design & Consultation: August 2, 2009 Spread Footing Cast -In -Place Concrete Retaining Wall Construction 581 Rocky Branch Lane Coppell, TX 75019 GT Project 2007005 Does not have any additional fill "behind the wall" (i.e. further towards the rear of the lot at the toe of new retaining wall construction. Fill in this area would not only philosophically conflict with observed conscientious maintenance of channel and lower lot landscaping, but would logistically and financially conflict with retaining wall construction demands requiring imported borrow. The claim that "...property owners in adjacent areas are being negatively affected during rainstorms because the flow of storm water is obstructed from draining properly" does appear supported by engineering observations but obstructions do not appear to be your retaining wall construction. Recommendations The request by the City that "...you immediately restore the ground between your wall and the drainage easement to the level it was prior to construction of the wall" is invalid. Grades at the toe of the new retaining wall and in your shared portion of the channel appear historically unchanged and therefore require no remediation on your part. Additionally, no legal drainage easement appears present at the toe of your wall or in your shared portion of the channel. Overall channel improvements may be beneficial but recommendations are beyond the scope of this engineering review. Feel free to contact me days at my office if you have questions or need additional information. Sincerely, Glenn Tracy, P.E. .. F �F 9s 1 . ............................... GLENN TRACY ................................ �o ..66285 ' /11i�sco.NA�- E�..�.. The seal appearing on this document was authorized by Glenn Tracy, P.E. Firm # F- 002575 on August 2, 2009. Engineering Design & Consultation: August 2, 2009 Spread Footing Cast -In -Place Concrete Retaining Wall Construction 581 Rocky Branch Lane Coppell, TX 75019 GT Project 2007005 Reviewed Original Construction Engineering Design & Consultation: Spread Footing Cast -In -Place Concrete Retaining Wall Construction 581 Rocky Branch Lane Coppell, TX 75019 GT Project 2007005 Excavation essentially complete. • Existing decayed crosstie retaining wall yet to be removed. • Partially complete excavated soil stockpiled to reduce imported borrow quantity. • Silt fence intended to prevent soil migration off -site can be easily seen. August 2, 2009 Footing forming complete. Excavation for toe key can be seen. • Additional excavated soil from toe key stockpiled to further reduce borrow quantity. • Original grades and associated sod can be easily seen at toe of wall. • Silt fence intended to prevent soil migration off - site can be seen retaining stockpiled excavation. Nearly complete masonry veneer. • Excavated soil from footing construction already replaced to behind the new retaining wall. • Silt fence can be seen still in place. • Maintained original grades can be seen at toe of wall. Engineering Design & Consultation: Spread Footing Cast -In -Place Concrete Retaining Wall Construction 581 Rocky Branch Lane Coppell, TX 75019 GT Project 2007005 Completed masonry veneer and masonry columns. • Maintained original grades can be seen at toe of wall. 6 August 2, 2009 Face of wall grading essentially complete. • Historically old flora and structures can be easily seen at neighboring lot to the north. • Silt fence can be seen still in place. • Maintained original grades can be seen at toe of wall. Engineering Design & Consultation: Spread Footing Cast -In -Place Concrete Retaining Wall Construction 581 Rocky Branch Lane Coppell, TX 75019 GT Project 2007005 Re- Reviewed Construction August 2, 2009 Engineering Design & Consultation: Spread Footing Cast -In -Place Concrete Retaining Wall Construction 581 Rocky Branch Lane Coppell, TX 75019 GT Project 2007005 Fully vegetated and maintained lower yard and shared channel with opposite neighbor. • Maintained original grades can be seen at toe of wall and along your side of the pipe culvert Existing and undisturbed tree and hardscaping on opposite neighbor's yard can be seen adjacent to pipe culvert wing wall. August 2, 2009 Fully vegetated and maintained lower yards /shared channel with opposite neighbor. Undisturbed pilot trench can be easily seen. • Historically old flora and structures can be easily seen at neighboring lot to the north. Constricted drainage channel between neighboring lots to the north. • In- filled swimming pool coping at your north neighbor's lower yard can be seen. Pool was anecdotally described abandoned due to repeated over - topping dating back many decades. Engineering Design & Consultation: Spread Footing Cast -In -Place Concrete Retaining Wall Construction 581 Rocky Branch Lane Coppell, TX 75019 GT Project 2007005 Historically old crosstie retaining wall and supported post/mesh fence approximately aligned along the pilot channel at the neighboring north, opposite side lot. • Mesh fencing appeared to capture debris flow from upstream. Channel flow would be expected to be impeded. August 2, 2009 Engineering Design & Consultation: Spread Footing Cast -In -Place Concrete Retaining Wall Construction 581 Rocky Branch Lane Coppell, TX 75019 GT Project 2007005 Reviewed Anecdotal Pictures (Provided by Cindy Frie) 10 August 2, 2009 Engineering Design & Consultation: Spread Footing Cast -In -Place Concrete Retaining Wall Construction 581 Rocky Branch Lane Coppell, TX 75019 GT Project 2007005 Pre - development of your back yard. Existing decayed crosstie retaining wall and modest channel side slopes compared closely to characteristics observed and described during and after new retaining wall construction. August 2, 2009 Existing topography on your lot leading toward pipe culvert compared closely to characteristics observed and described during and after new retaining wall construction. Note opposite neighbor's historically old flora placement at the culvert wing wall. Historical sedimentation and debris collection after recent storm events were described and graphically represented at north neighboring opposite lot. Mesh fencing captured debris from upstream and likely impede channel flow. Improper debris disposal into channel upstream likely exacerbated impeded channel flow and associated flooding. 11